Refined Wilding for Functional Biodiversity in Urban Landscapes: A Verification and Contextualisation

Abstract

Optimising existing knowledge sets and encouraging the integration of interdisciplinary study findings can facilitate the advanced functions of biodiversity required for sustainable urban landscapes. Urban Green Spaces (UGS) can reach across an urban landscape, including indoor environments. The existing and traditional knowledge sets and practices for urban development and greening provide extensive and pertinent guidance; they are however variably implemented. More recent and advanced knowledge sets where properly utilised can optimise and provide advanced function. When adequately brought together, advanced sustainability for urban landscapes can significantly improve global sustainability performance. This article uses the final step of classic grounded theory to contextualise, verify and define refined wilding as a substantiating concept for functional biodiversity as theory for urban landscapes and for sustainable urban development. Refined wilding works toward wild refined UGS that functionally connect across an urban space and landscape, including positive influential flows with grey and transparent spaces. Where used to guide urban design, strategies, vision and goals this concept can provide (i) a conceptual framing that optimises and encourages an organisation of interdisciplinary and advanced knowledge, improving and advancing sustainable urban development, and (ii) a specificity, and overarching and comprehensive guidance for various UGS types toward the positive outcome of functional biodiversity. Functionally biodiverse UGS and landscapes require lower maintenance and perform at an advanced level for human health, economic development, the natural environment, and built or paved environments and landscapes. In turn, addressing how human activity and modification of urban landscapes can significantly degrade human health and the natural environment, or underachieve. Refined wilding (i) substantiates functional biodiversity as a positive outcome for urban landscapes, with a balance between ecological functions and functions for human populations; (ii) considers quality, function, and connectivity of and between UGS and spaces where UGS could be introduced or improved; (iii) enables an improvement, and addresses common barriers to UGS accomplishing advanced functions for urban sustainability; (iv) encourages urban wilding by functional native and non-native selections, and natural and semi-natural UGS; (v) positively influences and is influenced by grey (built environment) and transparent spaces (blue/aquatic and air).

1. Introduction

Urban landscapes are primarily built environments resulting from human modification and, therefore, inevitably and significantly the result of human influence. The significance of human influence on sustainable outcomes in urban landscapes is evident in statistics reported by the FAO [1], which state that 2% of the world’s surface is urban, and by 2050, 70% of the world’s population will live in cities and urban landscapes. A total of 75% of natural resources are used by city inhabitants. The importance of sustainable urban development is recognised by various international organisations. The majority of waste and carbon dioxide emissions come from the urban landscapes where a significant number of the world’s population lives. Apart from CO₂ emissions, air pollution and hard surface and built environment development are also mostly caused by urban landscapes and development, with transport systems also responsible for changes in land cover types and air pollution, and industrial activity responsible for changes in land cover and air, water, and waste pollution. Transport systems are normally mostly in urban landscapes; however, they are also used to connect urban landscapes. Industrial activity is normally on the outskirts of urban landscapes or even in regional landscapes. These outcomes are in majority the result of human modifications and evidence of the human influence on outcomes for and from urban landscapes, by behaviour and urban development approaches. The reasons for giving adequate effort to sustainability in urban development and landscapes include climate change mitigation [2], clean air and water, and limited terrestrial and aquatic ecosystem degradation. These reasons as motivating factors vary by individual and organisational response.

Most international organisations refer to the relevant Sustainable Development Goals (SDG) and recognise the importance of mitigating the effects of urbanisation when detrimental to human development and the natural environment. These efforts take place in the era of the Fourth Industrial Revolution [3], which is defined by technological advances that integrate into daily lives. In most cases, this revolution is connected to a priority given to the principles of sustainability while also presenting some contradictions. The World Economic Forum (WEF) [4] refers to this revolution as human-centred and encourages the use of technologies for positive impacts. In this definition, sustainability principles can be used to guide and improve how new technologies are integrated into society, urban environments, and landscapes. In urban development during this Fourth Industrial Revolution, an increase in hard surfaces and infrastructure and reliance on artificial intelligence occurs. While some technological advances are sustainability-focused, they rely on manufacturing and components that are not. Therefore, a cultural shift occurs in the same era as improved guidelines and knowledge sets for sustainability. It is not, however, synonymous with sustainability, and efforts for sustainable urban development alongside this revolution are needed. Urban development is responsible for some of the most detrimental impacts on the environment, economy, and society, including human health. These impacts might not be worse than in the last century, but as more studies are conducted, they are more evidently proven to be negative and detrimental. The Organisation for Economic Cooperation and Development (OECD) [5], as a policy sub-issue, emphasises the need to address expanding urban environments and landscapes, ensuring they are green and low carbon as a matter of economic, environmental, and societal sustainability. SDG 11 is the most referenced by the OECD for sustainable cities and communities [6].

Urban open spaces (UOS) are a range of urban space types (UST) [7], referred to as a matrix of different UST, urban green spaces (UGS), urban grey spaces and urban transparent spaces (air and aquatic). UGS are also referred to as ‘softscapes’, as compared to hard urban environments, referred to as grey (built environment and informal) spaces, provide a connection across grey and green spaces [8] and transparent (aquatic and air) spaces as natural-environment in and of an urban landscape. All UST are interconnected and interdependent, and they influence each other. UGS provide significant advantages for improved sustainability outcomes. The quality of each space type is as important as the proportions of grey to green to transparent. The proportions of each UST are also significant, as are spatial distributions and where each is located compared to others, and as compared to human activity and residence. Maintaining connectivity and function of the natural environment across a built environment of human settlement, transport, industrial activity, or other use is by this consideration significant. The natural-environment as biodiversity is introduced here. Bukvareva [9] discusses optimal biodiversity as a variable according to urban landscapes and systems and easily reaches an intention for biodiversity across urban landscapes to address diminishing ecological function. Mayrand and Cleargeu [10] suggest a need for 3D connectivity across urban green roofs and walls and a need for further research into the design and maintenance of green buildings to resemble UGS to ensure functional landscape connectivity between grey spaces, which emphasises how different UST are influential to each other.

Functional quality and connection between space types and differences within the same space type is a significant consideration for urban biodiversity and could inform valuation of and policy for UOS [11]. As grey space, the hardening of urban landscapes,, increases, biodiversity losses are representative of diminishing ecological function and decreases in structural and functional biodiversity, which can lead to consequences for humans and limit the benefits that nature can provide [12]. There is evidence of variably increasing and decreasing green spaces dependent on the city and country; in some cases, significant decreases [13]. Rapid urbanisation, high density and shrinking cities, are a few of many reasons for this variability. These trends in urban development, some understudied, example the importance of urban planning for development, and evidence an opportunity for planning that can address SDGs for urban development. Even an opportunity for specific conceptual guidance that is conducive to sustainable development goals, as they contribute to decreases in urban and spontaneous greening, limiting a planned preventative greening that functional biodiversity encourages. Decreases can have an effect on various functions of UGS by system and landscape [13,14] and for human health. An ‘enabling environment’ which consistently encourages UGS, particularly functional UGS, despite adapting populations and infrastructure caused by shrinking or high density cities, or rapid urbanisation [14] could be facilitated with improved use of guiding concepts. An improvement by concepts that can capture what is required for the various UGS types as compared to existing terms and concepts that can but, in some cases, do not by use or definition might more adequately plan for sustainable urban greening.

Nature-based solutions, novel ecosystems, and renaturing are examples of recent terms that intend improved urban sustainability outcome. These terms, renaturing, for example [8,15], consider specifics like green roofs and forests but not all UGS types to address urban heat islands and floods. Novel assemblages for novel urban ecosystems of ‘biotic, abiotic, and social components’ [16], where native plants are preferred and aesthetic preferences are addressed. The specifics of native compared to wild require defining, with native as plants that naturally occur, by arrival or origin, and in most cases indigenous and hybrids or cultivars of native plants are defined as native. Wild plants are not cultivated and are grown in natural ecosystems, and can grow in semi-natural ecosystems. The recommendation for native and low maintenance is common for UGS [17], with less reference to wild plants or systems. Teixeira [16] recommends and encourages an improved understanding of the novel urban ecosystem concept from the landscape architecture discipline and gives examples of how this knowledge set can contribute [18]. Rega-Brodsky [19] recommends an increase in studies of taxa diversities and suggests that limited studies linking biodiversity to ecosystem function in 5% of the literature reviewed might limit an understanding of solutions. They recommend research that encompasses a greater diversity of taxonomic groups and urban systems, focusing on biodiversity hotspots with multidisciplinary approaches for addressing and achieving urban biodiversity across urban landscapes. Behm [20] recommends trait-based research to address the limited understanding of urban biodiversity associated with functional dimensions to improve outcomes from studying and increasing biodiversity. Most urban biodiversity research recommends understanding ecosystem services, which can be limited to monetary values. While understanding the monetary value of biodiversity can increase motivation, functions of biodiversity that might have indirect monetary values are important to research and improve upon. Some researchers [10] find that simplified interventions with native species of plants and shrubs can provide a functional structure for urban landscapes, emphasising the importance of function at low cost through low maintenance. These studies introduce an idea of ease for simplified UGS of ecological function while proving how more complex UGS of ecological function improved functional connectivity might require design and variable maintenance.

With these various recommendations, terms, and knowledge sets, which have mostly similar intentions but are variably expressed by language and specifics of intention, this article:

(I)

Suggests an improved understanding of how wild and diverse UGS can improve sustainability in urban landscapes could be required, alongside implementation strategies that ensure function.

(II)

Suggests urban landscape design can improve the ecological function and natural- environment aspects of an urban landscape, but it requires improved language for intention to care, ‘cues to care’ [21], for a design to be able to ensure positive outcomes [22] from implementations and guidance provided for human natural-environment interactions (HNEI).

(III)

Verifies functional biodiversity as a viable positive outcome for UGS and urban landscapes and refined wilding as a substantiating concept. It is a new term for urban landscapes that has improved specificity for responsive guidance for urban development.

(IV)

Uses Grounded Theory Methodology (GTM) and a literature review to verify the term and substantiating concept for relevance and fit in the urban landscape context, how it addresses a main concern [23] and is complementary by intention and can improve on existing terms. Agricultural wilding as a preceding substantiating concept provides some basic conceptual framing for analysis and assists in contextualising refined wilding and functional biodiversity for the urban landscape. How wild productive systems are different from refined wilding design principles is a significant indication of how refined wilding is different from agricultural wilding and how ecological sensitivity within human realities (ESHR) [22,24] aligns design changes by landscape type and specific conceptual guidance. The three literature reviews analyse UGS types, advanced studies, and search term results. They provide initial verification of refined wilding as a substantiating term for functional biodiversity in urban landscapes. They are analysed and organised using this theory and concept as a conceptual framing that additionally verifies and contextualises the relevance of functional biodiversity and refined wilding. The methodologies review definitions of different UGSs in an effort to address different functions and define functional outcomes. This drives refined wilding toward a biodiversity function for different UGS types, adequately addresses the main concerns [23], and takes advantage of opportunities for urban trends. Eventually, refined wilding is verified as achieving a functional biodiversity that satisfies all UGS types and that can improve the quality of all UGSs, which is suggested as capable of improving the quality of other UST and of the urban landscape for the typical functions of an urban landscape and for advanced function, including the opportunity to decrease health care costs.

(V)

Brings functionality to biodiversity, and functional biodiversity is an aspect of UGSs that can reach urban landscape sustainability by functional connecting. The functions of UGSs are hypothesised to be determined and dependent on an adequate response to most advanced studies from various relevant disciplines, a well-defined intention of outcome, and being specific while adaptable to local context concepts. As these studies continue to advance and improve, an approach for comprehensive reach in guidance is suggested.

(VI)

Provides by definition of the concept, refined wilding as guidance for design approaches that achieve a wild refined UGS which can be further supported by the existing terms, renaturing and novel urban ecosystems, and by existing disciplinary understandings and practices for the urban landscape. It is, by principle, a design system for functional biodiversity that encourages function and efficiency in planning and implementation by long-term outcomes that maintain efficiency and function with minimal maintenance. The land type, UGS, is the defining space and its influence on and connection to surrounding landscape and space types.

(VII)

Refers to UGS as urban green spaces, but also uses urban green systems.

(VIII)

Introduces urban transparent spaces as air and aquatic spaces in urban landscapes.

1.1. Urban Green Spaces

The various types of UGS are listed as gardens, residential or public, forests, parks, cemeteries, corridors, rooftops, and walls. They have various uses and are all designed differently for use and function. UGSs inevitably influence and connect to other natural- environment urban spaces, including transparent (air and aquatic) [25], and grey (informal, undetermined use and vacant land, occasionally with spontaneous greenery) spaces.

Green spaces in urban landscapes are not specifically associated with the Fourth Industrial Revolution other than being a space type that could decrease with built and hard surface development. It is very much encapsulated in SDG 11, but further goals and reference to them could improve an understanding of why UGS of various types are important to either maintain and conserve and/or reconstruct for landscape connectivity and how they can be further implemented and of improved function for environmental, societal, and economic outcomes. The following SDGs, SDG 3: Good Health and Well-being; SDG 9: Build Resilient Infrastructure (with the definition of resilient providing an opportunity for relevance); SDG 12: Responsible Consumption and Production; SDG 15: Life on Land (which brings considerations to an environmental level, not only urban, with an opportunity to justify the reason for the built environment); SDG 16: Peace, Justice, and Strong Institutions (effective, accountable, and inclusive institutions at all levels, which can address the negative and detrimental impacts of unsustainable urban development, for this article, caused by decreasing green spaces); and SDG 17: Partnerships for Goals and Strengthening the Means for Implementation, by allocation of funds, are all conducive to, support, and can improve an understanding of the importance of functional green spaces for each individual UGS as a system and for urban and outside of urban landscape sustainability by connectivity. There are various programs, initiatives, and studies that emphasise the urgency and importance of conserving and increasing UGS as gardens or other UGS types. Land cover and UGS coverage in 1039 cities across the world was 38.46% with a 20.27% standard deviation in 2015, with UGS accessibility at 82.67% with a 22.89% standard deviation [26,27]. Coverage, as stated in 2015, is difficult to determine sustainability significance without expectation of coverage and above-average accessibility [27]. Accessibility is determined by subjective and objective measures, including attractiveness, urban land use pattern, and impact on UGS spatial distribution. A residential garden is not included in these statistics for accessibility.

1.2. Functional Urban Green Spaces

The definitions of UGS have developed in the last thirty years [28], from urban forests to inner city green spaces. The connecting influences to and from urban transparent space (air and aquatic quality) furthers understanding of the significance of UGS for sustainability and advanced function [29].

The term function must address the significant human interaction and population in urban landscapes by use, health, and impact on the natural-environment. Functional biodiversity is a desired outcome for urban landscapes, and green spaces are a specific aspect of sustainable urban development relevant to the outcome. Green spaces significantly connect grey and transparent (air and aquatic) urban spaces to the aerobiome and air quality (sound and sight). The various functions are biodiversity conservation, stormwater, water regulation, heat mitigation, air quality regulation, aesthetics, and therapeutic benefits [30,31]. UGS have been proven to mitigate emissions [32] and improve water quality (through grasses as water filtration and regulation [25]) and human health. Specific to tree canopy as compared to grass cover [29], air quality and pollen exposure risks have been proven to worsen mental health [33,34] and symptoms of various diseases despite the proven therapeutic and health benefits of high-quality green spaces. UGSs are also proven to improve air and noise pollution and mitigate heat waves or long-term increases in heat and, therefore, climatic shifts [32,34]. Through connectivity, their function reaches across the urban landscape, with paved and built environments and informal spaces (grey spaces) easily becoming functionally biodiverse and contributing to landscape-level function and connectivity. Functionality is determined by human interactions with the natural environment and design. How and whether UGS are planned as connecting spaces across a landscape determines sustainability outcomes. As a specific example, improvements that accommodate and even improve human health where interventions for UGS are refined for function could focus on the quality by influence on and of human health as well as accessibility. Where influence on human health might be negative, behavioral changes can decrease negative influence, and lower the importance of accessibility. Defining functional for purpose and quality is, therefore, a significant factor.

1.3. Functional Biodiversity for Urban Landscapes

For this article, functional biodiversity refers to any biodiversity across an urban landscape, and for this reason, the different types of UGSs are listed. Function specifically intends to better understand human use of the landscape and how biodiversity can be functional. Advanced function by benefits of functional biodiversity, as well as some of biodiversity’s harmful outcomes is an additional consideration and intention.

Functional biodiversity was originally a term or theory introduced for the agricultural landscape; it is substantiated and defined by the ESHR concept [22]. In previous work, the ESHR concept has been verified using grounded theory. Biodiversity has several definitions and is variably understood as needed or beneficial for agricultural landscapes. The ESHR concept encourages an understanding of it as ecological interactions and processes at the system and landscape levels and the human realities of any study landscape, as novel urban systems and renaturing are referred to for social factors. Urban landscapes present a different yet similar challenge for positive biodiversity outcomes. Functional biodiversity is therefore suggested as a theory for urban landscapes as the ESHR provides substantiating that can be applied to the landscape type.

For agricultural systems, a GTM identifies productive intention by yield and harvest as the main concern [23] and even a barrier to improved positive outcomes, as well as additional factors of access to resources, capability, and personal preferences. For agricultural wilding [24], wild crops and plants are defined as non-domesticated and growing in a productive system.

In urban landscapes, biodiversity and the natural environment are an addition to the built environment and infrastructure and to the significant human population, which is different from agricultural landscapes in purpose and composition of land use types. In other explanations, biodiversity is hardened and degraded by urban landscapes and arguably needs a conservation approach. In urban landscapes, wild plants can grow spontaneously in self-maintaining populations and in natural or semi-natural ecosystems that can exist independently of direct human action. In most cases these spontaneous plants are not as accepted for urban landscapes for matters of aesthetic and safety preference [35]. Wild systems can also be refined for urban purposes, and the purpose can be determined by the type of UGS. Norton et al. [36] provide some definitions of biodiversity from urban gardeners, and Delahay et al. [37] provide a review of biodiversity in residential gardens. Goddard et al. [38] consider biodiversity and its conservation to be a scaling up from gardens.

Function of biodiversity for urban landscapes refers to a balance between the two aspects of the ESHR concept and, particularly, an understanding of function for purpose by UGS type, and landscape connectivity, across UGS and across different UST. In ecological terms, it refers to plant, tree, shrub, and grass (PTSG) diversities, as well as taxa diversities in a system and across systems and a landscape, including influences on and from transparent (air and water) and grey spaces. The function of biodiversity for purpose can address and accommodate human interactions and intentions, which novel urban ecosystems intend to address.

1.4. Trends in Urban Development: An Example of Changing Landscapes and Opportunities for Refined Wilding and Functional Biodiversity

Where trends in urban development are properly or better understood, sustainable development and adaptability to unexpected changes are expected. The importance of adequately responding to emerging trends for sustainable development is a reason to ensure responsive and well-guided adaption and development.

Shrinking cities is the example of an understudied urban development trend. Other trends of conserving or improving sustainability in high-density cities and managing informal connections between different UST are in discussion. Shrinking cities bring attention to pre-empting and planning urban landscapes as an opportunity for sustainable development and as responsive to local urban landscape circumstances.

1.4.1. Shrinking Cities

By 2050, 37% of all cities will be impacted by the shrinking cities trend. This provides an opportunity for parallel efforts of greening and planning for newly organised decreases in urban-centred populations, referred to as planning for ‘compact cities’ [39,40], which can work toward SDG 11 and other Sustainable Development Goals. The trend of shrinking cities is studied most in developed countries and is a point for urban development and planning [39,40,41]. In some cases, it is understood as a decrease in urban population with increases in surrounding areas, often called suburbs. The decrease can be to accommodate intensive or densely populated cities that cannot sustainably accommodate residence or professional activities or for reasons of employment or living preferences, with sustainability influences of waste management and energy consumption as examples. The reorganisation of population distribution as a vertical and horizontal distribution is often understood as the opposite of urban growth. Suburban sprawl is also, however, defined as an urbanisation trend, and increases in suburban populations are seen as a shrinking city trend. Shrinking city trends are, therefore, often an observation and study of urban population organisation and distribution across a range of urban landscape types. Wu et al. [39] provide an analysis of published work on the topic and emphasise the importance of understanding and studying SCT as a point for planning, particularly in regard to sustainable development. They define SCT as a socio-environmental consequence that is often indicated by an economic downturn and population decline. This population decline is in parallel to increasing global populations.

Most shrinking cities trends are different in eventual settlements and population distributions, and influence on built environment and infrastructure. The demographic influence is in birth rates (caused by infertility, lower childbirth by choice, or urban settlement shifts), which has different demographics populating urban centres (elderly, gender distribution, and labour market), which is observed to be similar in all shrinking cities trends. Some shrinking cities are caused by changes in natural resource availability and industrial changes, with the closure of single-company towns and impacts of environmental hazards leading to changes in employment opportunities and housing affordability as reasons for population redistribution trends. In many cases, economic shrinking and restructuring can influence housing and the location of populations [41]. This can result in vacant land and various built environment adaptions that, without adequate planning, can result in further detrimental impacts.

This urban trend provides an opportunity for prevention and planning as aspects of development, as population changes can result in urban development in any case. It, therefore, makes sense to take these trends as opportunities in already changing urban landscapes and in already variable quantity and use of UGS, instead of leaving these changes to detrimental developments that are contrary to the intended goals of sustainability or other principles. The implications are often negative for human health and human preferences, and for overall sustainability goals.

1.4.2. Urban Green Spaces and Examples of Urban Planning

The decreases [12] and inconsistent uses of UGS and urban landscapes might be, in a substantial knowledge environment, evidence of limited uptake at a planning level and of decentralised local planning and implementation. Examples of UGS planning prove an enabling environment. FAO guidelines [1] for urban and peri-urban forestry emphasise the importance of an ‘enabling environment’ with several country- and city-level examples of strategies led by inter-departmentally developed initiatives, including a common vision with unified goals across councils, inclusive green planning, and building capacity to manage. These examples are relevant to UGS often defined as gardens, as well as to urban forests. Examples from these guidelines, including policy development mapped out with visions, principles and implementation for some significant green city and urban strategies demonstrate how a guiding concept could be relevant and useful for policy, strategy, or common visions across departments or across several of the same departments or councils.

1.4.3. Responsive Guidance for Trends in Urban Development: Functional Biodiversity

Conceptual guidance could lead to responsive guidance for any trend, or common urban development activity that focuses on UGS. Not only to guide urban development, but for assessing and planning for urban development. Several terms and concepts can be used to guide urban planning activities amidst changing urban trends and development, and in normal urban circumstances. Terms and concepts that guide planning and practices need to be organised and defined as conducive to best practice for various circumstances. In these cases, conceptual guidance that brings the most relevant terms and concepts together for advanced outcomes is recommended. In response to shrinking cities trends, to ensure sustainably planned development. They could also improve already well guided strategies, visions and goals for urban development [1], if used to assess the urban landscape. An ability to reach the most relevant and advanced terms for improved sustainability outcomes is a step toward preventative and advanced guidance that can adequately respond. UGS would be conducive to adaption to these trends. Functional and biodiverse UGS could therefore be one of the focuses or responses for adapting to this trend, and for other trends.

The theory of functional biodiversity [22,24] for urban landscapes could provide responsive guidance, particularly where design approaches are used and guided by refined wilding. Functional biodiversity is defined as a combination of ecological functions across systems and landscapes and human functions that address various human realities of different urban landscapes. It is suggested that the more sensitive we are to the human influence on functional biodiversity outcomes by knowledge and understanding of what it means and how it can be implemented [25], the more advanced and widespread these positive outcomes will be. Where used to guide HNEI for several UGS, an urban landscape can achieve functional ecological connectivity that also functions for human populations. With its emphasis on wild crops and PTSG, alongside ensuring an ecological and human realities function conducive to functional biodiversity with associated management and design techniques, refined wilding can reach a vision, principle, and implementation level conducive to influencing policy, city-level strategies, across departments and geographic locations within a city and across cities as an urban landscape [1] (p. 11). In design, various advanced functional biodiversity aspects can be factored in to advance sustainability outcomes, as a common word used for urban landscapes [1] (pp. 36–47).

2. Materials and Methodologies

This article uses step seven of classic grounded theory [42] to verify and contextualise the relevance and fit of functional biodiversity for the urban landscape for any time and place [43]. It is a methodology that ‘discovers theory using data’ from various methods and processes of reflection and triangulation, where the researcher stays ‘impartial and with a neutral mind during the seven-step process’. The reflective and triangulation processes eventuate to coding core categories by relevance and, eventually, to theory and concepts, which initially identify a main concern [23] and words or terms and concepts that define or even intend to solve the concern. The methodology required to identify a main concern is considered a complex method of analysis [27,44]. These words, terms, and concepts are eventually verified by literature and ‘library-based research’. Functional biodiversity is already a substantial theory verified by five concepts [22,24]. The preceding classic grounded theory was for agricultural wilding, an advanced term for rewilding the agricultural landscape used as a substantiating concept for functional biodiversity outcomes in agricultural landscapes [22]. The more specific term and outcome, wild productive systems, is suggested as improved for landscape context and relevance. A classic grounded theory process is a theory-building process to explain and understand a phenomenon and often works to identify a main concern [23,45]. It is often initiated from fieldwork and observations, processes of coding, comparisons and contextualising, and identifying key categories, then a verification with fieldwork to narrow down the most significant and relevant categories that adequately address the main concern [23]. It is in the final step of grounded theory that contextualising outside of one’s own findings begins, and it is traditionally a literature verification.

This article illustrates this step to verify outside of the author’s own understandings from fieldwork, coding, identifying key categories, and from previous classic grounded theory completed and published for agricultural landscapes, to verify the grounded theory of functional biodiversity for the urban landscape, using refined wilding as a substantiating concept. The literature review as step seven of classic grounded theory verifies and contextualises the relevance of functional biodiversity as a positive outcome for urban landscapes and introduces and explains refined wilding amongst the existing literature as a substantiating and specific concept for this positive outcome in urban landscapes. It uses the methodologies to define and explain functional biodiversity outcomes for the urban landscape using refined wilding as a substantiating concept. UGS are the basis for the article, with refined wilding and functional biodiversity definitions as relevant to these spaces verified. In doing so, it further explains complementarity with existing terms and niche opportunities for improvements. As is recommended for novel urban ecosystems, disciplines and practitioners already influential in urban landscapes can input, contribute, and be guided by this theory and substantiating concept.

How trends in urban development require maintained sustainability intentions and opportunities is also explained. These trends, including shrinking cities [39,40,41] and the challenges of floods and urban heat islands, which renaturing [8] intends to address, are easily included in trends that require and provide an opportunity for UGS improvements. How responsive guidance to these trends from strategies, visions, and goals for urban development can be better guided by the introduced term and concept then forms a basis for the article and recommended use for the term and substantiating concept. This article, thus also intends to explain how functional biodiversity and refined wilding can provide an overarching and specific term for such guidance and implementation.

2.1. Data Filtering and Classification Procedures

The data filtering and classification process used for a literature review is informed by completed grounded theory processes [42,43,44,45] and fit and relevance by verifying the main concern [23] and relevance of functional biodiversity for the urban landscape. The conceptual framing, which provides analytical guidance for filtering and classification, is this basis and informing factor. UGS, different types and if functional biodiversity can reach by definition and relevance every type and, therefore, fit the urban landscape context; advanced and specific studies that verify the main concern and recommendations to address the concern; and if functional biodiversity and refined wilding fit and are relevant to recommendations to address the main concern. Results from search terms to verify and determine the existing use of the term or concept in the study.

2.2. Conceptual Framing and Preceding Theories and Concepts

Functional biodiversity and refined wilding provide a conceptual frame for analysing literature review results. It assists in verifying relevance and responsive ability to interdisciplinary and specific study findings. Design is not a conceptual frame for analysis but is included in the literature review as an implementation tool that can be guided by refined wilding principles for functional biodiversity outcomes. Refined wilding is a term or concept that builds on other concepts toward functional biodiversity as a grounded theory of positive outcomes for any landscape.

Table 1. Three concepts that provide a conceptual frame to analyse literature reviews.

Functional Biodiversity	Agricultural Wilding and Wild Productive Systems	Refined Wilding
Functional biodiversity is a verified grounded theory substantiated by five published concepts developed using a classic GTM. Ecological Sensitivity within Human Realities (ESHR *) is the substantiating concept [22] that can guide HNEI to positive outcomes for agricultural landscapes.	Agricultural wilding [24] is a term introduced for an agricultural landscape. The resulting system is defined as a wild productive system. The definition of wild crops and plants is clarified and well-defined. Wild productive systems can satisfy the productive intention and various other human realities that are occasionally proven to impede functional biodiversity outcomes in these landscapes. It is the result of an analysis of traditional definitions and uses of rewilding using ESHR as a schema for the grounded theory of functional biodiversity. This schema is also used to analyse four farm designs and results in an ESHR-aligned farm design [46] implementation tool for agricultural wilding. The analysis relies on a literature review and determines the appropriateness of coffee farming landscapes.	Refined wilding provides semi-natural ecological systems in urban landscapes that are composed of wild plants, trees, shrubs, and grasses (PTSG). Wild PTSG are non-domesticated and in systems that are not human-modified. Refined provides differentiation and expectation of human modification; wild PTSG are native and non-native functional selections. Urban agricultural and community garden spaces could use functional biodiversity and wild productive systems as relevant outcomes for improved functional biodiversity outcomes. The other UGS types are not normally productive but instead for aesthetic function for resident or public use and, in some cases, address health benefits. Wild refined UGS is a term introduced for other UGS types. As a design approach, refined wilding provides initial and general design principles for the urban landscape. It works from some specific aspects of ESHR-aligned farm design [46].

* ESHR provides consistent conceptual framing as a general concept and provides specific aspects that frame the conceptual analysis of the three literature reviews and guides design principles that are furthered with refined wilding.

provides a further explanation of each concept.

2.3. Three Literature Reviews

The three literature reviews provide (i) a definition and overview of different UGS types with the relevance of refined wilding summarised, (ii) a summary of specific and significant study findings that can improve and inform refined wilding for advanced functional biodiversity outcomes, and (iii) a summary of three search term results. All three literature reviews contextualise functional biodiversity and refined wilding as a new and viable concept for the urban landscape and are a final step of classic GTM. The first two literature reviews provide a similar type of verification and contextualisation of commonly used terms for the study landscape. All literature reviews and search term results are analysed using the conceptual framing.

2.3.1. Literature Review I

UGS is the term that most adequately summarises and generalises landscape spaces that are easily designed to be functionally biodiverse. An overview of how refined wilding can be relevant and improve different UGS types and urban landscapes emphasises required improvements in studies about UGS to achieve sustainability goals for urban landscapes and cities. More specific intentions and outcomes could ensure the quality of achievement. The literature review for UGS types and definitions are from existing knowledge determining search terms: urban forests, urban gardens, urban green roofs and walls. Search term results from literature review III also provide further definitions of UGS. See

Table 2. Different urban green space types and refined wilding.

UGS Types and Refined Wilding
Urban gardens and forests
Urban gardens and forests represent microhabitats, ecological niches [46] and, at times, an overlooked opportunity for functional urban biodiversity that can connect across an urban landscape. Urban forests provide a different use and function for sustainability principles and categories; they also, however, provide an opportunity for functional urban biodiversity that connects across an urban landscape. Urban forests [47] provide advanced complexity in all aspects of natural environment systems, including wildlife-friendly functions. They are not likely to be residential individual-use systems. Soil multi-functionality and biodiversity in below- and above-ground interactions and processes are relevant considerations for urban gardens, but also for urban forests. They provide microhabitats where plant diversity has a positive effect on soil fauna and multi-functionality and for diverse taxa. Urban gardens of different types, residential (individual or shared), community, public, rooftop and wall or ceilings, will often provide functional complexity in particular aspects, for example, soil and plants, and indirect functions for human well-being, as well as protection for the natural environment beyond its own system. Several studies indicate important landscape design considerations to address and integrate. For example, a decline in community garden biodiversity and a need for green hard surfaces and connectivity between garden plots and other green spaces [48]. Tresch et al. [49] find that intensive management decreases plant diversity, and urban gardens should have plant diversity and engage in soil protective management practices, including applying compost and mulch and avoiding soil tilling to improve urban biodiversity. They find that anthropogenic assemblages can achieve such urban biodiversity outcomes. Individual preferences in aesthetics, safety, or other aspects can lead to higher maintenance and less complex, less native, less wild, and less biodiverse systems. Wildlife friendliness and wildlife conservation in urban landscapes improve with the use of residential gardens [50,51,52], which are dominant UGS types.	Advanced design principles and techniques are suggested to increase and achieve urban biodiversity outcomes. Watering and soil tilling were two significant factors in structuring soil fauna and plant communities which can be managed to avoid reducing urban biodiversity outcomes. Urban gardens and forests can, therefore, be encouraged, maintained, or improved with refined wilding principles and associated ESHR-aligned garden and forest design approaches [46]. The challenges of ensuring continuity across individually owned gardens are recognised and need to be addressed. Most urban forests are, by category, functionally biodiverse and ecologically complex UGS.
Urban agriculture
Urban agriculture, like traditional agriculture in rural landscapes, is often prioritised by productivity. Urban agriculture is often more adaptable to various functions and uses rather than just a productive function, with the population also influenced by urban sustainability principles. Management techniques can result in urban agriculture benefiting the natural environment as well as humans [53]. However, the agricultural and productive intention does differentiate a community garden system in an urban landscape from an urban agricultural system. The biodiversity outcomes from urban agriculture, from gardens to farms with livestock, therefore, vary and contribute variably to landscape-level ecological connectivity and function. Defining urban agriculture is suggested as dependent on an urbanisation gradient, as agricultural systems have very similar intentions and definitions with location, with the urbanised area being the most significant defining factor. It can also be differentiated from urban gardens for the definition of agriculture, which often has several of the same tree or plant as a crop harvested for subsistence or for sale. In urban gardens, while there can occasionally be several of the same plant or crop for harvest, these examples are closer to urban agriculture but stay within an urban garden definition. Urban agriculture is then defined when a closer to standard or traditional agricultural system is located within or close to the population of an urban landscape and is managed by urban populations.	Refined wilding and design approaches aligned with ESHR for functional biodiversity [22] outcomes are relevant for urban agricultural systems; however, agricultural wilding [24] is relevant as well, with wild productive systems more likely to result. It is, therefore, an example of how refined wilding can result in wild productive systems.
Urban green rooftops, walls, and ceilings
Urban green rooftops and exterior walls often result in climate variability and heat mitigation from hard surfaces in urban landscapes. They provide additional benefits, with air and water quality and noise quality by photosynthesis, filtration, and insulation from external noise and air provision, with some aesthetic benefits depending on a user’s preferences. Green interior walls and ceilings, which are not always urban but in most cases are, provide a different function, including noise insulation and air quality, including scents and filtration [54,55] and aesthetic benefits that are associated with health benefits, by relaxation and other hypertension factors [55,56]. Green roofs, walls, and ceilings perform differently than urban parks, forests, and gardens when discussing air pollutants and aerosols. They provide a different function for human health via mitigation, and expectations for design are, therefore, different but can be guided by the same parameters for urban landscapes by optimised requirements. These differences include how they regulate air pollution, contribute to pollen and allergenic aerosols, and how they mitigate heat radiation and filter or capture water.	Design approaches and refined wilding are relevant for these green space types, and exterior UGSs are most significant for ecological continuity across an urban landscape. As refined wilding works toward functional biodiversity, these factors for consideration can easily be integrated into a refined wilding design approach.
Urban green corridors
Green corridors provide a connection between traditional UGS for various purposes, including fauna, pollinator, and insect habitat or forage, transport corridors, air quality, temperature regulation, or just an aesthetic function. They, therefore, provide a significant opportunity for ecological continuity between UGS and can be influenced by aesthetic preference and function, with selections determined by preferences.	Refined wilding as a design principle and a guiding concept that balances between aesthetic preferences and advanced functional biodiversity outcomes.

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2.3.2. Literature Review II

The second literature review selects advanced studies for urban landscapes that integrate considerations of human health and UGS. They emphasise specific points for functions that refined wilding and functional biodiversity can address. They lead to a summary of important considerations and findings that can further specify and improve refined wilding as a conceptual guidance and design approach for functionally biodiverse urban landscapes. In most cases, where they are understood as integrated points influential to refined wilding design, they can assist in providing advanced functions of any UGS and urban landscapes. Human health and ecological considerations are overviewed with (i) air quality and complex considerations as recommendations and as relevant to refined wilding and (ii) existing and relevant terms for urban landscape development and UGS as relevant to refined wilding summarised. These advanced studies result from the search results from literature review II, which are informed by two searches: functional biodiversity and UGS, and functional biodiversity and cities. Literature searches are informed by significant terms and findings from these searches.

Table 3. Strategies and recommendations for pollen exposure.

Significant Considerations and Findings	Strategies and Recommendations for Pollen Exposures
Allergenic rhinitis affects 4 million people, reduces life quality, and burdens the health care system. Kabisch et al. [57] list clinical symptoms, including dermatitis, rhinitis, and respiratory complications such as asthma and symptoms indicative of worsening mental health [32,33]. Air pollutants and pollen types and counts influence allergenic symptoms.	Improved prevention of allergic symptoms of pollen allergy sufferers is considered a significant strategy, with symptom burdens, ozone or air pollutants, and pollen concentrations coordinated with behaviour change [58]. Determining different pollen types and different concentrations using in situ monitoring of pollen and forecasting that provides a finer scale with continuous implementation can improve the availability of relevant information for risk and recommendations for behaviour adaption. Recognising the significance of air pollution and ozone for humans and UGS. Reducing air pollutants. Urban development strategies, including considering eco tones between urban and regional or rural landscapes to address pollen exposures from outer urban landscapes. Providing allergenicity [59,60] findings by contextualising for human population, pollen type, air pollutants, and UGS type is essential. Urban planning at the system and landscape level, differentiating UGS planning strategies and studies to minimise the negative health effects on urban residents, such as allergies. Improve the risk information available and use it to improve opportunities for improved targeted behaviour changes, which can reduce medical treatment needed. Low risk according to pollutants combined with pollen exposure by different UGSs.
Higher concentration on a hospital rooftop as compared to a park of allergenic pollen from PTSG with different symptoms as compared to urban parks [55].	UGS-specific findings, design, and behaviours are required. Proven decreases in air pollutants in and because of UGS and between UGS (rooftops had higher allergen symptoms among the exposed as compared to a park). Ensure education and understanding of different UGS types and higher allergen symptoms. Ensure the public utilises the information and adapts behaviour to reduce the risk of exposure. Ensure different UGS are designed for specific use and type, and for continuity across UGS and urban landscapes.
Pollen interactions and merging with air pollutants, which leads to the majority of pollen particles creating allergen containing aerosols, worsen symptoms amongst the exposed. Limited studies of pollen counts, concentrations, allergenic thresholds, and behaviour change.	Lower pollen particles that are allergenic with strategic and functional selections and spatial distributions of native and non-native plants. Lower air pollutants. Studies and designs that consider specific and comprehensive indicators for measurement and responsive design. Measures include tree and grass types, pollen types, and varying pollen concentrations and thresholds for allergenic symptoms. Designs for UGS should maintain diversity in PTSG. Include non allergenic trees, shrubs, and grasses in UGS with maintained native plant diversity.
Summary	A functional design that finds a balance between these specific considerations of air quality and ecological function by system and landscape can provide an advanced function for urban functional biodiversity.

,

Table 4. Advanced knowledge for functional design: allergenic species and pollen season.

Allergenic Species and Pollen Season: Advanced Knowledge for Functional Design
Allergenic PTSG are normally only a problem in the flowering season, for three months of the year. In most cases, wind-pollinated and species identified as the most harmful by aerosol exposure are to be avoided but can be managed with adapted human behaviour and locations away from high air pollutant rates. Urban landscapes are surroundings that rely on transport networks and can be considered higher in air pollutants, alongside manufacturing and mining locations. As allergens vary by region and climate, the variables to consider that support country- and regional-level studies for accurate estimations of risk will factor in types of allergens, pollen, air pollutants, moulds, mites, and other microbials from outdoor and indoor exposure [54,55]. Hasnain et al. [61] find that sensitisation to different indigenous pollens and moulds varies by country and region, determining allergenicity [59,60] as a regional and country-specific finding.	Regional and country-level studies are required to determine estimations of risk to allergens, pollen, and air pollutants. Indoor and outdoor exposures require study and consideration.	Allergenicity is region- and country-dependent. Sensitivity to pollen and air pollutant exposure is human-dependent. Indoor and outdoor exposure risks must be monitored.
Recognising the allergenic potential of UGS is relatively unproven or unknown in detail of native and non-native species, additional studies have found that non-natives, while not necessarily less allergenic than natives, have different flowering seasons and, therefore, lengthen the pollen season and potential risk of exposure. In a study of the allergenic properties of 56 dry grasslands, 30% were allergenic, and most were natives [62]. From this study, the pool of non-natives contributed a larger biochemical diversity of allergens and flowered later than natives. The policies, strategies, and design and implementation of diverse, non- or low-allergen UGS vegetation must take the combination of native and non-native vegetation into account and must consider and monitor the abundance of allergenic species. This study suggests urban area populations are more susceptible to allergens; this might be qualified with air pollutants and UGS type.	Different flowering seasons and abundance of allergenic species and pollen. Air pollutants are regulated differently according to UGS type.	Functional selections that limit pollen season are required. Monitor the abundance of allergenic species and pollen content. Adapt behaviour to limit air pollutant and pollen exposure risks. Functionally biodiverse UGS can regulate air quality.
Trees or shrubs that are high in pollen and rely on wind include cypress, box hedges, and pine trees. Avoid trees such as alder, birch, ash, Willow, elm, olive, mulberry, and white cedar. Pollinator-reliant PTSG are less likely to contribute to pollen-containing allergenic aerosols. Ref. [63] Non-obvious flowering PTSG are to be avoided. Ref. [60], wattle trees, native wildflowers pollinated by insects, birds, bees, etc., are less likely to be allergenic and, therefore, negatively impactful to human health. Diverse landscapes with many different plant types minimise the amount of pollen from any one species. Asters, goldenrods, and coneflowers are examples. Exceptions to the rule include cypress pine which are Australian native and allergenic trees.	Wind-reliant pollination increases a species’ allergenicity; pollinator-reliant species are less likely to negatively impact human health; Diversity in species can minimise the amount of any one type of pollen.	Diverse pollinator-reliant selections of PTSG could minimise the risk of pollen exposure in urban landscapes. Natives and non-natives are allergenic.
Some studies consider the potential allergenicity of tree species to determine risks to human health. There are limited regulations for planting and maintaining allergenic versus non-allergenic in urban landscapes [13,14]. These regulations can be informed by improved and updated measures of the allergenicity of different tree and plant species, referred to as the value of potential allergenicity (VPA). Two studies in the Mediterranean found species, or native species provide further information about allergenic risks [59]. Some studies provide information about the allergenicity of each tree species, and other studies further analyse to determine the risk of an entire urban park, using VPA, the surface of the urban park, the number of species in the park, and the area occupied by each species and height of each tree. Composition and configuration by spatial distribution and arrangement of tree species are factored into this study. With these factors formulated, the urban park is rated for allergenicity risk, which is informative to the design and planning of UGS [64]. Across the Mediterranean, 41.3% of common Mediterranean urban trees from 150 urban forest species (trees and shrubs) have moderate- to very-high allergenicity, and they are not all native species [60].	VPA varies by country and is not entirely determined by native species. Various trees and shrub species have different allergenicity.	Allergenicity is more significant than native selections. Local and regional studies of VPA are required. Planning and design must be responsive to these findings. Regulations could be required.

and

Table 5. Advanced existing knowledge for consideration addressed by refined wilding.

Improved Understanding: Existing Knowledge Sets of Biodiversity in an Urban Landscape	Examples of How Refined Wilding Can Improve a Green Urban Space from Existing Knowledge Sets *
‘Ecological continuity’ from community gardens for urban biodiversity
Community gardens for ‘ecological continuity’ [43] and urban biodiversity, particularly when located in urban spaces, are determined by plant diversity and are almost continuously proven as beneficial. More precarious is considered for building land, and non-precarious on non-building land. The non-building lands can provide an ecological corridor with diverse and functional plant species selection and continuity by corridors across the urban landscape. With significant community garden coverage, the loss of community gardens is considered to represent a significant risk to ecological continuity. The emerging threats to garden biodiversity include their replacement by development, conversion to hard surfaces, and declining plot sizes. The points of connectivity between garden spaces and neighbouring plots are important with declining plot sizes. Adaptive green hard surfaces for connectivity are suggested as capable of addressing how biodiversity across an urban landscape with connectivity can provide biodiversity impacts of intensively diverse garden spaces. These hard surfaces could be adapted to UGS, rooftops and walls, or footpaths and roads of partial green surface coverage.	Refined wilding is relevant for any green urban space introduced to adapt to hard surface introductions. Landscape design provides not only an opportunity for human control and intervention for a biodiversity outcome but, when guided by a particular concept, can further encourage an intended outcome. With refined wilding guiding landscape design or urban gardens and green spaces, native and wild crops and plants are integrated at minimum proportions. The function of these systems is reliant on aspects of ESHR, which factors in human realities of the landscape and of each individual designing and maintaining and/or using the garden or green space, alongside ensuring an ecological function within the system, between garden and green urban space systems and at a landscape level. The importance of ecological niches for garden systems [46] as a complementary schematic analysis and considers different farm design approaches with a conceptual analysis guided by an ESHR-aligned design approach. The ecological continuity referred to for conservation and functional biodiversity for community gardens, or inclusive of community gardens, is determined by PTSG selection and spatial distribution. Therefore, determining which design can be guided by refined wilding.
Novel urban ecosystems.
NUEs [13,14,65,66] emphasise the importance of native plants for UGS and some of the human barriers to seeing native plants further implemented in various UGS types. They also emphasise the importance of conserving semi-natural systems in urban landscapes. Spontaneous plants, lack of safety, and invasive risk provide an argument for design and structured terms for all urban ecosystems, as well as a need to address non-native plants and spontaneous plants (unattractiveness, lack of safety, and no cues to care) [21].	Refined wilding provides design principles and intentions for a functionally biodiverse green space. It can address and refine spontaneous plant green spaces and improve the ability for human care and control of any UGS. It encourages native plant inclusion and functional native and non-native selections for various additional functions. A refined wilding UGS would, therefore, suit the definition of a novel urban ecosystem; also, the informing concept, ESHR, considers continuity and function across a landscape and with other UGS that are geographically close, alongside continuity and function between urban and outer-urban landscapes.
Novel landscape designs
Design provides cues to care and a level of human control. ‘Design makes NUEs more acceptable by providing guidance for intervention’ [65,66,67] for professionals, but without findings for users of NUEs. Li and Nassauer [21] find that design provides cues to care by providing human control for organising and providing new uses and encourages a landscape approach for design [68]. Design makes NUEs more acceptable by providing defined guidance for intervention. The value of design is further supported for intervening and making native and biodiverse gardens and urban spaces functional, ecologically and for human purposes. The level of human control it provides can facilitate conservation and ecological continuity, not just by maintaining and conserving with realistic creation and maintenance strategies but with the function and complexity of ecological structures in each urban community garden or green space. Landscape designs that are novel are likely influenced and guided by knowledge sets organised within advanced concepts.	Landscape-level consideration of functional biodiversity encourages consideration of ecological connectivity between different green spaces and the creation of UGS and urban gardens, even on hard surfaces and built-up areas. Refined wilding furthers the functional ecological connectivity of such garden and urban green systems, with further implementation guidance provided with complementary schema and terms developed [21,31]. As refined wilding suits definitions of novel urban ecosystems and provides design principles, it addresses suggestions for and provides a novel landscape design. It also complements Carinanos et al.’s [60,69] informed design with health outcome focus suggestions for urban trees and parks.
Wildlife friendly
Wildlife-friendly urban systems emphasise the importance of landscape connectivity and the management of gardens as a collection of gardens across scales from neighbourhood to city [44,45,46,47]. For an urban landscape with a limited intention for productivity as a spatially continuous intention across systems or landscape patches in a landscape, wildlife diversity or populations are encouraged or conserved with gardens, whether individual/residential or community. Van Helden et al. [51] discuss wildlife-friendly gardens with ponds, bird baths, and shelters for rare and endangered native species, contributing to biodiversity and conservation. Hwang and Jain [52] encourage landscape design for urban wildlife conservation, with design examples provided for an urban city. They suggest urban landscapes as opportunities for wildlife conservation, which require improvement across cities. Larson et al. [50] suggest residential gardens and ‘yards’ as significant opportunities to contribute to and support wildlife habitat in urban landscapes. Habitats and corridors for wildlife do not always need native or closer-to-wild urban green systems to be supportive. Plants more than grass are often found in wildlife supportive residential gardens. To retain viable populations, a landscape ecology framing is needed which can provide biological corridors and safe movement between UGS. Assigning particular spaces for wildlife to find habitat in urban landscapes can also address safety and impacts on built environment structures. The influence of human behaviour on wildlife and other taxonomic groups is almost as important to control as the threat of some wildlife to humans.	Where biodiverse UGS encourage wildlife and other taxonomic populations, they also provide more opportunities and encourage the importance of functionally biodiverse UGS that provide habitat and corridor function between habitat and forage environments. A refined wilding system can better support wildlife-friendly UGS by addressing human realities. The different needs and preferences of individual gardens and yards as compared to public parks and other UGS types can be accommodated. Individual gardens and yards are considered significant for wildlife-friendly urban landscapes. Human realities include safety and human health associated with wildlife abundance in urban landscapes; examples include human/wildlife interactions and zoonotic disease. With these factors well addressed in implementation and design, the resistance to wildlife-friendly UGS could decrease. ESHR encourages landscape ecological framing as an analytical schema that leads to refined wilding as a new term for the urban landscape. Intra-system considerations of an individual garden and of connection to neighbouring habitats or landscape patches can provide a system-to-system understanding of landscape ecology and connectivity. Design can improve landscape ecological connections and functional biodiversity outcomes. These considerations can be addressed with refined wilding-influenced PTSG selections across an urban landscape, particularly as ecological connectivity across an urban landscape can adapt design spaces for such purposes.
Meadowscaping
Integrating native grasses and meadows can provide a sustainable alternative to traditional grass for residential or public gardens or parks [19,36]. Multi-layered vegetation, including tree canopy, might better address human health and functional biodiversity outcomes.	With variable findings regarding lawns and maintenance, refined wilding encourages an understanding of native grasses and maintenance approaches. However, meadows without tree canopy can provide sufficient function. All selections for advanced function are non-allergenic, have a limited pollen season, are not wind-pollinated, and are able to regulate air pollutants.

* Examples provided in this section are existing terms used by various landscape architects, gardeners, urban designers and planners, and ecologists. They emphasise how the inclusion of wild crops and plants and diverse plants, and using design systems can improve functional biodiversity outcomes and address human opinions of what is acceptable, safe, aesthetically pleasing, and manageable. In urban landscapes, addressing human opinion is as important and required as the ecological principles for functionally biodiverse UGS.

lists significant summaries of advanced studies and findings for interdisciplinary use.

2.3.3. Literature Review III

The third literature review includes three literature searches and provides verification and contextualisation of refined wilding using functional biodiversity as a search term for urban landscapes. The literature review is step seven of the classic GTM for relevance and contextualising of refined wilding and functional biodiversity for an urban landscape as a positive outcome. Three searches are conducted, and the frequency of terms and similarity by intention to be verified are understood as indicative of how refined wilding substantiates functional biodiversity for an urban landscape. Thus, how appropriate functional biodiversity is for an urban landscape, and if functional biodiversity is an already used term. The conceptual framing for search term results further assists in verifying these terms for the urban landscape and uses ESHR as well. ESHR provides in-depth substantiating. These searches are conducted using Google Scholar as an example of used terms and concepts for the urban landscape. The search terms are selected to determine how commonly specific terms and words are found in the published literature to verify the relevance and originality of refined wilding and functional biodiversity for an urban landscape. The first search is ‘functional biodiversity and UGSs’ with 159,000 search results and 960 results reviewed. A total of 110 results were listed as title and journal, and the next 850 results were reviewed for significance and relevance by titles, summaries, or abstracts according to search terms. The second search is ‘functional biodiversity and cities’, with 159,000 search results and 960 results reviewed. The third search is ‘Design, functional biodiversity, urban’, with specificity search results by terms included referred to. The journals by discipline are analysed for interdisciplinarity in urban landscape studies and practice. The different UGS types found in search results are also identified and listed as an indication of being frequently studied or occurring. Most of the search results inform or further literature review I and II.

3. Results

Three literature searches and reviews evidence and verify the relevance of refined wilding and functional biodiversity for urban landscapes and their reach in organising and analysing urban landscape studies and terms. This verification process proves encapsulation by interdisciplinary and advanced studies for optimisation.

3.1. Literature Review I: UGS Types Defined as Relevant to Refined Wilding

Table 2 provides definitions for UGS types and how refined wilding could improve the quality of each UGS type. There are more categories of UGS found in literature review III.

Summary of Literature Review I

UGS of different types have different functions and require different designs. Various studies indicate knowledge sets that recognise the relevance of refined wilding and functional biodiversity. The findings evidence different landscapes and UGS contexts by UGS numbers, function, and type. They justify the term refined, as for human preference, design, use and interaction that is more consistently required, as the population in urban landscapes is significantly higher, a need for appearance and precise development for urban purpose and function is needed. Refined wilding encourages semi-natural or natural ecological systems that are refined for reasons of significant human population and can reach across a landscape with functional connectivity, resulting in functional biodiversity for an urban landscape which is responsive to individual UGS and landscape circumstances.

3.2. Literature Review II: Advanced Study Findings

3.2.1. General Findings of Significance for Functional Biodiversity in Urban Landscapes

Wildlife and Urban Landscapes

Urban landscapes are often built environments that, without ecologically functional biodiversity, can be detrimental to natural environments and to wildlife through land clearing and human activity. Urban environments and humans can be detrimental to wildlife and their safety. In some cases, keeping wildlife out of urban development is better for humans and wildlife, as they can be detrimental to each other. It can, however, be better for wildlife to have biological and travel corridors and connections between their habitats and across urban developments, particularly across roads. The impact of taxonomic groups, including wildlife, reptiles, and insects, in more biodiverse and native gardens and green spaces is another human consideration, with impacts on health and safety. The emphasis on the cause of impact and considerations can depend on the country for urban development, with some taxonomic groups presenting significant threats to humans and human settlements, by preferences or physical or health safety, and urban developments presenting a threat to wildlife and other taxonomic groups. Wildlife can be defined as various taxa, including mammals, reptiles, and pollinators, as examples. Different wildlife have different functions for natural environment systems.

Plant Species Selection for Taxonomically and Functionally Diverse Areas

With refined wilding, the selection of native versus non-native plants and crops for any residential or community garden and urban UGS, even on and in buildings or hard surfaces, can provide ecological continuity and encourage an understanding of plant species, with spatial distributions informed by design systems for functional biodiversity. With intended input and outcome, wildlife and taxonomically functional diversity can also be designed for at the individual, system, and landscape levels. The following three points are for further consideration as associated with plant selections.

Functional Attributes of Native and Non-Native Species

Refined wilding brings attention to how an urban garden system can be of minimum proportion with wild crops and plants (native and close to native). In most cases, an urban landscape will maintain plants, but community gardens and various human functions and intentions for a residential garden or public garden in a hard-surfaced and/or built-up space. It, therefore, encourages an understanding of realistic intentions for any urban garden system that includes native or wild varieties of plants or crops. Native and non-native selections do require functional arrangement or assemblages [49] for advanced performance, including limiting pollen season and ensuring a semi-natural system of low maintenance.

Meadowscaping Lawn and Grasses: Selections, Diversities, and Maintenance

Grasses in UGS are common in parks and gardens. Maintenance required for conventional lawns is proven to decrease biodiversity despite aesthetic preferences [15,70,71]. Meadowscapes of wildflowers and native or functional selections of wildflowers and grasses result in low maintenance and functionally different systems of improved ecological complexity but are aesthetically different [62,71]. They can also have health implications and benefits [56,57,58,59,60,61,63,64,70,72,73,74,75,76].

Human Health

Kondo et al. [70] and Nguyen et al. [29] recommend an improved understanding of the advanced function of UGS for human health. Health outcomes from complex green spaces require a balance between hazardous health outcomes from some UGS related to pollen exposure and air pollutants. The health benefits, which lead to sense scapes and other functions explained in the above section, are not essential for human health. Physical activity can often provide health outcomes without UGS, where inequity in access to UGS exists [11,19] and where UGS are dysfunctional and can degrade human health. The argument for increasing UGS without an advanced function, as accessibility to UGS studies often recommend, requires improvement to ensure that UGS do not impede health outcomes and are ecologically functional. This is often referred to as the quality of UGS [19], which can improve the benefits of physical activity. UGS are also studied and recommended for other therapeutic effects that improve health and recovery from disease, including cardiovascular disease and cancer. Ref. [54] Finding the right balance between health benefits as compared to impeded health outcomes and degraded health from UGS is, therefore, a significant recommendation. Specific advanced points for pollen exposure are in the following section and in Table 3 and Table 4.

3.2.2. Specific and Advanced Study Findings for Functional Biodiversity in Urban Landscapes

Air Quality: Pollen Content by Count and Type, and Pollutants

There are studies that indicate a worsening of air quality and impacts on human health caused by air pollution combined with pollen in the air [57,59,60,61,62,64,73,74,75]. The effect of pollen count and air pollutants on human health depends on pollen type, human health status, human exposure, and air pollutant levels. There are abilities to adapt behaviour at a population level around pollen seasons. There might, without these control factors, be an increased argument against wild PTSG that produce allergenic pollen and are wind-pollinated. Equally, an argument for functional UGS and an argument for decreasing other pollutants in the air is supported. In many cases, the additional air pollutants are caused by CO₂ emissions of different categories, which are, in the majority, caused by urban development. It is argued that improvements in sustainable urban development and practices could reduce air pollutants and, therefore, the negative impact of pollen content on human health. The difference in pollutants by green space type is a factor for consideration, as is how green spaces mitigate against air pollutants. An additional factor is the plant selections as non-allergenic species and pollinator-dependent selections, with limited pollen seasons and spatial distributions by structure, complexity, and ability to regulate air quality and pollutants. A functional design of UGS requires health-related adaption with adapted use and decreased pollutants, providing acceptable levels for allergenic selections in a green space. UGS are proven to improve air, noise, and water quality. When used by humans, they can provide additional health benefits, including relaxation for physical and mental health [27,28,29,32,33]. The negative health influence of pollen-allergenic exposures, which are often attributed to different types of UGS, street trees, and other PTSG that have allergenic pollen, are numerous and significant. Kabisch et al. [57] list clinical symptoms, including dermatitis, rhinitis, and respiratory complications such as asthma and symptoms indicative of worsening mental health [27,28,29,32,33]. The health benefits of high-quality UGS are proven for allergic respiratory conditions, cardiovascular conditions, and psychological well-being [30,55]. It is, therefore, important to state that the design and selection of PTSG for any UGS, including isolated greenery and street trees, must be functional in this manner, diverse but non-allergenic and limited in pollen season. It is important to recognise that adequate monitoring, availability, and use of information for pollen count and risk of exposure is essential and can result in behaviour changes that can mitigate the risk of exposure [58], decrease medical treatment costs, limit risks to human health, and limit counteracting health benefits from high-quality UGS. Alongside are adequate strategies for behaviour change to reduce the risk of exposure, and reducing air pollutants that interact and merge with pollen particles to create allergen-containing aerosols, which worsen symptoms among the exposed, lowering exposure risk. Additional considerations from studies like Kabisch et al. [57] indicate different risks of exposure to allergen-containing aerosols with pollen particles on rooftops as compared to parks and that pollen counts and types can be from other UGS or isolated greenery. These factors must be taken into consideration for safe and high-quality UGS for people with allergies. Where allergenic PTSG are native selections, these behaviour changes can accommodate and limit negative health outcomes by adapting behaviour to avoid close to or above allergenic thresholds of pollen and allergenic aerosols and worsening symptoms. Additional strategies include reducing air pollutants and lessening pollen particles interacting and merging with pollutants in the air. Lowering of pollen particles is achieved by selecting native and non-native plants that can lower the risk of exposure. The lowering of risk to exposure and allergenic aerosols is also in lowering air pollutants. These considerations are specific and informative to the term function and functional biodiversity for an urban landscape and support the need for an advanced function to address these more complex findings. Refined wilding can provide a system of design principles that provides an advanced function for topics of air quality and exposures that significantly risk human health. The combination of pollutants and pollen exposures can be addressed with selections of PTSG that are non-allergenic and native and have a limited pollen season, lowering risk to human health by risk of exposure while maintaining time or exposure to UGS. The location of UGS that are allergenic could also be strategically planned for habitant behaviour [58] to adapt around pollen season, lowering exposure and, therefore, health risks, without significant changes to daily activities. These considerations provide a functional biodiversity with advanced performance for urban landscapes.

Existing Terms and Practices for Urban Green Spaces and Refined Wilding

Urban development and planning is a long-standing discipline and knowledge set, informed by several different design systems, landscape architecture, urban planning, and development professionals, as well as gardeners and landscape gardeners. There are well-established terms, concepts, design approaches, and practices for biodiversity in urban landscapes. These existing knowledge sets and practices have informed some of the more advanced biodiversity outcomes in urban landscapes but are not consistent or far-reaching enough to provide landscape ecological continuity nor a system-level ecological function in every UGS. Most studies find the importance of green infrastructure, greening hard surfaces, and integration of native plants. The categories of UGS vary by type and PTSG and flowers in them, and the type of green space by intended use and function, including gardens, filtration systems, aesthetics, air purifying, shade, and noise insulation. The multi-factor consideration is encouraged with the new term and can address the most needed considerations for functional biodiversity outcomes. Table 5 summarises some advanced considerations and relevant and significant study findings that can be addressed by refined wilding and functional biodiversity.

Summary of Literature Review II

There is adequate knowledge provided in the published literature on the topic of UGS and biodiversity using native PTSG. Grasses are given significant consideration, in terms of intensive maintenance as compared to native meadows and allergenic grass selections. Intensive management is considered negatively impactful. These considerations are biodiversity-focused but not human-health-focused. Nguyen et al. [29] find that tree canopy in UGS can benefit human health more than grassland. This point leads to findings related to air quality but also other health functions of UGS, including water, air and noise filtration and regulation. Some studies indicate sufficient knowledge in professionals and less knowledge in users of residential UGS [15,56,70]. Refined wilding and functional biodiversity for UGS and urban landscapes encourage an advanced function and consideration of humans as well as biodiversity and ecology aspects; it informs literature reviews and organisation and identification of significant study findings for recommendations for design. It also provides realistic recommendations for an increase in functional biodiversity across urban landscapes, recognising that UGS vary by number, size, quality, and accessibility by city and country. As refined wilding encourages wild UGS systems as semi-natural or natural ecosystems with lower maintenance requirements, professional design or access to relevant information for residential UGS is recommended. The point of landscape design for urban wildlife conservation is integrated into ecological continuity. It emphasises the importance of landscape-level functional biodiversity, which provides ecological function and addresses various human realities [21].

3.3. Literature Review III: Relevance and Verification of Refined Wilding and Functional Biodiversity for Urban Landscapes

This search provided 365,000 results, with 1800 reviewed. A total of 110 were reviewed in detail for the first search, and 12 for the second search, then the title and summary of article review for the remaining 1678 articles. A total of 82 relevant terms for functional biodiversity in the urban landscape were found, and only 2 articles that specifically used the term functional biodiversity were found. Sixteen UGS types were found in the literature review and are expected to be equally as improved by refined wilding and the intended positive outcome of functional biodiversity as they could be for the advanced, existing, and complementary terms found. Sixty-nine journals published the findings from search results and different disciplines, including ecology, public health, cities and planning and policy, science, building, landscape architecture, urban ecology, biodiversity and conservation, sustainability, monitoring and assessment, environment, land use, and urban forestry. This range of academic and peer-reviewed journals or theses is considered representative of the interdisciplinary of UGSs and sustainable urban development that considers terms relevant to functional biodiversity. The search results for each term selection indicate specific aspects of functional biodiversity studied and limited focus on design. When design is specifically in search terms, results are more specific and relevant to refined wilding and functional biodiversity. The results for each search are organised into core categories with relevant terms connected to each category; see Figure 1 and Figure 2.

Biodiversity is often included in search results, but the term functional biodiversity is not often used. Many studies from search results encourage increases, improvement and consideration of human aspects for functional biodiversity in UGS and cities. The variable purpose is defined by UGS types, connecting biodiversity and green space types across a landscape. These space types are from the literature search defined as green, blue (aquatic), and grey (informal or undetermined use, urban vacant land) spaces, and then air quality considerations, such as aerobiomes, aerosols, pollutants, pollen count, and ground-level ozone, and indoor microbiome [54,55], which can respond to and accommodate observed trends. Air quality considerations are influenced by and influential to these UST by sound and sight functions, as well as influence on human health affected by air. UST are eventually categorised in this article as green, grey (built environments and informal spaces), and transparent (air and aquatic). The different UGS types are determinants of function and optimisation of biodiversity and provide parameters for refined wilding design and guidance.

Table 6. Search term results: ‘Functional biodiversity and Urban Green Spaces’.

Functional Biodiversity and Urban Green Spaces
(Diversity 11) (Biodiversity 12) Functional Functional diversity (2) Functional ecology (2) Functional connectivity (2) of a structure of green space network Functional roles Functional ecosystems Functional specificities of wild bee communities (refined wilding) Functional riparian corridors Functional specificities Functional habitat network Functional group Functional biotope Functional spontaneity (refined wilding) Function of urban parks Functional urban green space types Functional habitat network Functional diversity and urban bird Functional traits Ecological functionalities Functional and taxonomic biodiversity approaches Species richness to functional community structure. Linking functional and structural connectivity Multi-function Multi-function by human use Multi-scale landscape patterns Multifunctional (4) green infrastructure Multifunctional design of sustainable drainage (blue or aquatic space with green space) Multifunctional urban green space (2). Bioretention swales as multifunctional landscapes Spontaneous vegetation: more than weeds Province trees Diversity Structural diversity Diversity of urban birds Spatial patterns and drivers of plant diversity. Plant species diversity (refined wilding) Mammal diversity Identifying diversity Tree species diversity and composition Soundscape diversity (layers of vegetation and trees) Urban forest diversity Taxonomic diversity Butterfly richness and diversity	Ecological Avian ecological diversity Ecological quality Landscape heterogeneity Private trees as compared to urban forests Sustainable urban futures: ecological approach Plant/pollinator interactions Trait-based Ground dwelling anthropoids Parasitoid wasps Overabundance of species Vegetation structure Urban Urban biodiversity Urban ecosystems services Urban green connectivity and multi-functionality Urban green space dynamics Urban ecosystem regeneration (refined wilding) Urban green space standards Urban residents value Landscape Landscape structure and function (2), edges and adjacent Landscape connectivity Landscape construction and bird diversity Ecology of air Composition Vegetation structure and composition across UGS types ‘Composition and structure of the local plant community’ Composition and functional diversity of urban flora Habitat Habitat network construction Habitat fragmentation and connectivity Animal habitat construction Native Indigenous plants Native or exotic Role of natives in urban greening Plant native Native and non-native: role in urban pollinator networks Wild Wild flowers Design Assemblages (refined wilding and design	Additional search term results by relevance Renaturing (refined wilding) Green Neighbouring green network and landscape metric Restorative urban green spaces Green corridors in urban landscapes, domestic gardens Green roofs Urban green networking Regreening the metropolis Green infrastructure (2) Regreening (2) Human preferences Mental and physical fitness and cultural dimensions Aerobiomes Urban green space Effects of UGS on water partitioning Urban green networking Restorative urban green spaces Effects of UGS on water partitioning Vegetation structure and composition across UGS types Role of natives in urban greening Urban green space standards Multifunctional urban green space (2). Functional urban green space types Biodiversity in urban green spaces Functional urban green space types Urban green space dynamics Quality green space Effects of UGS on water partitioning Green space characteristics Green space functionality Quality green space Green space characteristics Land surface temperature and green spaces Biodiversity Biodiversity patterns Biodiversity in urban green spaces Integrating biodiversity Maintenance and biodiversity Nature connectedness and biodiversity Fungal biodiversity Facets of biodiversity: edible forests Tree biodiversity Increasing biodiversity Spontaneous biodiversity Trait-based approach for sustainable benefits of biodiversity

and

Table 7. Search term results: ‘Functional biodiversity and Cities’.

‘Functional Biodiversity and Cities’

Functional Functional networks of green spaces: landscape spatial patterns Functional roles: integrating biodiversity as a non-human stakeholder Functional traits Functional biodiversity metrics Functional spontaneity Functional corridor connected green areas Functional traits for species Functional, structural and aesthetic aspects Wild Wilding cities for biodiversity Wildlife friendly Biodiversity Biodiverse city Biophilia: urban biodiversity for biophilic cities Biodiversity in gardens Air Aerobiomes Air quality (2) Aerosols with pollen particles

Green Urban green infrastructure Quality urban green spaces (2) Common green connectivity Ecology Hierarchical filters Community assemblages of urban species pool Ecological continuity Plant selections Multi-layered vegetation Native Native plants Native plants, grasses, and trees Native meadows Novel Novel urban ecosystems Novel landscape design Planning Reorientation Meadowscaping vs. lawns

list search term results organised by more defining categories.

Table 8. Journals of search term results.

Journal and Disciplinary Knowledge Sets from Research and Practice

Biology Biological conservation (3) Biodiversity and conservation (3) Bioscience Biological reviews Journal of biological diversity Urban biodiversity Plant archives Ecology Urban ecosystems (8) Ecological engineering (2) Journal of applied ecology (2) Ecological indicators (2) Ecosystem services (2) Journal of applied ecology Urban ecology Ecology and evolution Ecological Ecological applications Frontiers in ecology and the environment Austral ecology Ecography Energy, ecology and environment Journal of animal ecology Eco cities Journal of urban ecology Frontiers in ecology Basic and applied ecology Ecological research Trends in ecology and evolution Medical and health British medical bulletin International journal of environment and public health World Health Organisation (WHO) Oencologia Frontiers in microbiology Cities Making green cities Greening cities forms and functions Economics Beyond CBA

Sustainability Sustainability (2) Frontiers in sustainable cities Sustainable cities and society Sustainable development Current opinion of environmental sustainability. Centre for sustainable infrastructure development Journal Urban Urban forestry and urban greening (5) Landscape and urban planning (3) Contemporary urban design thinking Science Science and pollution Scientific Report Nature and science Science and the total environment Science and policy Journal of land use science Social science European journal of social science research Plurality, diversity and multicultural Frontiers in psychology Environment Environmental research (2) Environmental research Building and environment Mobility and environment Environmental monitoring and assessment Floresta y ambience Landscapes and land use Doctoral thesis: landscape architecture Conference on landscape and urban horticulture Landscape research Journal of faculty of architecture Land use policy (3) Land (2) Remote sensing ISPRS Remote sensing Revista

lists journal disciplines by most defining categories, and

Table 9. Examples of terms that are relevant to functional biodiversity and refined wilding design.

Relevant to Functional Biodiversity and Refined Wilding

Vegetation structure Multi-layered Native selections Assemblages Landscape design Novel ecosystems Aesthetic preferences Human safety and health: air quality, pollen and wildlife, vector-borne disease, zoonotic disease. Capability: design and maintenance Non-allergenic native selections Adapted human behaviour in pollen season Pollen and air quality UGS type, air quality and human health Heat mitigation Water filtration Ecology of air Landscape connectivity Noise and soundscape

Landscape connectivity Spontaneous greenery Green corridors Green space connectivity Wild cities (functional and refined) Biophilia Aesthetic preferences Sensescaping (scents, visual, sounds) therapy and health Ecological continuity across paved (grey) and urban green spaces Mammals, insects, and fauna included in urban biodiversity Wildlife friendly Tree canopy, green roofs vs. vegetation for human health and air quality Air, noise and water quality: impacts on respiratory, skin, and mental health [28,29,32,33]. Biotope Meadowscaping Renaturing

lists examples of terms that are relevant to refined wilding and design for functional biodiversity.

3.3.1. Functional Biodiversity and Urban Green Spaces

From these results, approximately 82 terms were identified as having similar meanings or intentions. There are no results with the exact term functional biodiversity and a few recurring terms. The terms are identified as significant or relevant for several reasons, including function, which includes a function for biodiversity, but also for human purpose and reason. The terms identified indicate a knowledge and practice that is relevant to this term as an intended outcome for UGS. UGS are also defined differently and are of different types. The various terms provide examples of the reach and scope that the term functional biodiversity has, and how refined wilding is relevant and can address the practices or recommendations of most articles in the search results. After 100 results, the search results remain relevant and become specific. The most significant organising of terms and considerations from summaries of search results are UGS types and terms that are conducive to refined wilding for functional biodiversity. There are additional and more specific terms that relate to human health. They are listed in Table 6 and advance how refined wilding and functional biodiversity can be understood, defined, and used. Table 6 is graphically represented in Figure 1.

3.3.2. Functional Biodiversity and Cities

A total of 12 article results listed as title and journal provide initial examples of more specific terms included, and the term functional biodiversity is found twice: as a reference to ‘functional biodiversity’ and ‘functional biodiversity metrics’. In further search results, functional biodiversity is found in 3 articles from 710 to 980 articles: ‘structural and functional biodiversity’, ‘functional and taxonomic biodiversity’, and ‘functional dimension of biodiversity’. Similar terms with ‘functional’ are not significantly found. The next 970 results were reviewed for significant and relevant titles or summaries. Abstracts according to search terms provide terms of similar meaning and significance; some are more specific to searches that include UGS. They provide additional examples of meaning and use for refined wilding and biodiversity. The terms that are of similar meaning and significance are more specific to the meaning of functional biodiversity for refined wilding. They include ‘Functional ecology’, ‘Functional traits for species’, ‘Functional corridor connected green areas’, ‘Functional spontaneity’, ‘Functional networks of green spaces’, ‘wilding cities for biodiversity’, ‘Functional roles’, and ‘Functional uniqueness vs. redundancy’. Some summaries include functional alongside terms for functional biodiversity, including aesthetics and structural. Disciplinary terms that are associated with ‘functional biodiversity’ include indoor and interior design as connected to the natural environment, which has some connection with the outdoor design of UGS. These findings are not specific to green spaces; however, most are relevant to these spaces, such as urban biodiversity or city biodiversity. These terms are different and are added to identified terms of similar or relevant meanings in Table 7 and are graphically represented in Figure 2.

3.3.3. Design, Functional Biodiversity, Urban

Search terms that include design: design, functional biodiversity, and urban, provide 294,000 search results with design in the heading, the title of the article, and/or in contents for the majority of results. Most refer to design, design frameworks, and design systems, with further reference to design tools, schemes, approaches, attributes, and conceptual design. The results that refer to design are specific to the search term, functional biodiversity, and terms included in the other search results, including green infrastructure, urban, city, functional connectivity, habitat, ecosystems, eco-engineering, functional connectivity, functional GI, multi-functional, and landscape. The results provide more specific considerations for design for functional biodiversity and some advanced and complementary ideas. In most cases, design is in the article content and not in the title or heading of the article. In the first ten pages, 200 results have 22 results with design in the title of the article. Design provides more specific results, ideas, and findings that can complement refined wilding design for functional biodiversity in urban landscapes. The search results evidence an existing knowledge set, and some advanced studies and findings that guide design for the urban landscape.

3.3.4. Journals by General Discipline

Search results are from 66 different academic journals, 1 dissertation, and 1 conference. There are 12 categories of general disciplines for these journals: biology, ecology, medicine and health, cities, economics, sustainability, urban, science, social science, environment, landscapes and land use, and remote sensing, listed in Table 8. And graphically represented in Figure 3. The most frequently published journals are biological conservation (3), biodiversity and conservation (3), urban ecosystems (8), urban forestry and urban greening (5), landscape and urban planning (3), land use policy (3), ecological engineering (2); Journal of applied ecology (2), ecological indicators (2), ecosystem services (2), sustainability (2), environmental research (2), and land (2). The interdisciplinarity by journal indicates a range of study findings by search results and an indication not representation of the reach of the topics of functional biodiversity and UGS, and functional biodiversity and cities by discipline. The refined wilding and functional biodiversity concepts here provide a generalised but also specific definition guidance, which can reach these different disciplines and contextualise the studies and findings. These disciplines, by search results, also contextualise the relevance of the refined wilding term by the different studies and their various considerations.

3.3.5. Urban Green Space Types

The UGS types found in the literature review, that is UGS studied amongst search results, are listed and include particular blue (aquatic) space types. The UGS types listed are more numerous than standard UGS types studied or focused on. For example, renaturing often refers to and focuses on urban forests and rooftops. Advanced studies also indicate air space types for consideration, including aerobiomes, pollutants, pollen count and types, viruses, ground-level ozone and indoor microbiome, and considerations, which also require consideration for advanced function. From the search term results and literature review, fifteen UGS types with different functions and logic for design were found. For example, a rooftop, as compared to an urban forest, will logically lead to a different optimisation of biodiversity by ecological consideration, stratification, diversity of PTSG and taxa, and how it connects to other UGS and space types. The different UGS types will also determine and could improve how green spaces are integrated and less impacted by grey and transparent spaces.

3.3.6. Terms That Are More Relevant to Refined Wilding and Functional Biodiversity

Terms that are more relevant to refined wilding and functional biodiversity are listed in Table 9. They are examples of existing advanced knowledge sets that can be organised by or referred to as relevant to refined wilding design and functional biodiversity for an urban landscape. They are, therefore, considered of similar importance to literature review results from literature review II. Health studies also provide findings that support advanced function where adequately considered next to ecological studies for functional biodiversity. These studies can provide advanced comprehensive guidance that can further design and improve positive outcomes. It is, therefore, suggested that refined wilding can be used with confidence by various disciplinary experts and preferably by or for interdisciplinary use for better defined and guided intentions and interventions. These terms can be organised or included in refined wilding design to improve functional biodiversity outcomes in urban landscapes. They are of similar importance to literature review II of advanced study findings. These terms accommodate different urban landscapes and the interdisciplinarity of urban landscape development studies and practice, and the different UGS types. Novel urban ecosystems, ecological continuity, native selections, and air quality are existing terms that are relevant, similar, and specific to refined wilding and functional biodiversity for the urban landscape. Meadowscaping, wildlife, pollen exposure risk, and air quality are more original topics for the urban landscape that are relevant and improve definitions of refined wilding as substantiating functional biodiversity in urban landscapes. Native and non-native selections as significant for functional biodiversity aspects are even more specific examples for the urban landscape that can address human health as an essential consideration. Other studies provide recommendations that can address other advanced functions but require further refining for advanced functions. These specific examples further the importance of individually designed UGS that integrate refined wilding design into the urban landscape and neighbouring UGS and that factor in the UGS type and how they connect to each other across an urban landscape. Examples are air quality and PTSG and vegetation selection, which advance refined wilding to considerations of non-allergenic selections.

Summary of Literature Review III

Most terms in the search results and in general and advanced literature review verify refined wilding and functional biodiversity as a new term that can reach most of the relevant terms identified. As conceptual guidance toward functional biodiversity for urban landscapes, it can encourage a coordinated understanding of study findings that lead to advanced implementation and function. Of the numerous relevant terms in the search results, many refer to functional or biodiversity or words or concepts that are similar by intention (Table 6 and Table 7). Most concepts in the search results are within the scope of refined wilding, which is more specific than functional biodiversity for urban landscapes. Design in the search results improved the specificity of terms used and supports a significant relevance for the implementation of refined wilding and functional biodiversity for an urban landscape. These search term results determine limited use of the term functional biodiversity for urban landscapes and variable use of terms wild and refined within the context of functional biodiversity and urban landscape from various disciplinary studies. The knowledge set for functional biodiversity in urban landscapes is evident. Numerous terms, studies, and practices evidence interdisciplinary understandings of biodiversity and various functions in urban landscapes. There are extensive and specific advanced study findings for urban landscapes that reach health, ecology, landscape architecture, biology, social science, sustainability, and geographic information systems. They provide a range of considerations that verify ecological science for agricultural systems, with the different purposes and functions of UGS as compared to agricultural systems and landscapes being a significant differentiation. Examples include vegetation structure and above- and below-ground functional ecological conditions. There are some terms that already exist and provide similar guidance, such as sustainability with a balance between economy, environment and society, including renaturing, restoring to natural condition, and rewilding, as examples. UGS type is more extensive than the normal categories listed in review I. The more extensive definitions are considered for the intended function of urban biodiversity in optimised and quality terms. Their influence on and how they are influenced by transparent and grey spaces also depends on the UGS type. The advanced study considerations remain the same, and UGS design for all types will improve impacts on transparent spaces and, in turn, improve human health and long-term and indirect influences on the natural environment. Transparent spaces (air and aquatic) are integrated with green spaces, by reciprocal influence which is a point for improvement by design and research that informs design. The influence of and on air quality is also dependent on UGS type and urban landscape and is a significant design aspect. Advanced function is the term leading from functional biodiversity to an outcome for refined wilding. This concept can guide toward functional biodiversity for any UGS type and, by advanced function, ensure positive outcomes reach across space types, to grey and transparent, and limit negative impacts of grey and transparent spaces on the natural environment and on human health. The ESHR and functional biodiversity [22] provide consideration of how different UGS types can provide and achieve advanced function in biodiversity and landscape-level connectivity, improving sustainability outcomes when guided by refined wilding.

3.3.7. Limitations

The location of relevant articles by term inclusion is either by search engine providing terms that are relevant first and most used, then the term searched for, or a limitation of the search engine. Most terms found in earlier search results are relevant and most used for the urban landscape. The limited result of this specific term, functional biodiversity, in all search results is considered an indication of limited knowledge, awareness, and use, while terms found in search results are relevant to it, more specific and used or appropriate for the urban landscape. This is an assumption with recognition of limitations presented by the search engine used. Graphs by core categories are provided for the first two search term results, and journals by disciplinary fields, for design they are written into paragraphs.

3.3.8. Summary

The results verify (i) a contextual relevance for the urban landscape, (ii) refined wilding and functional biodiversity can reach the extensive knowledge set that is already used to improve sustainable urban development and can provide adequate design approaches, principles, and guidance for optimised functional biodiversity outcomes. Verification is by (i) how refined wilding is relevant to different UGS types and how it could improve or provide consistent conceptual guidance for functional biodiversity outcomes that suit the different green space types and complexities in function for each; (ii) advanced specific studies of various disciplinary fields reached by refined wilding and functional biodiversity, particularly evident when the ESHR is used to substantiate functional biodiversity for urban landscapes; (iii) how search results for three different term combinations indicate limited use of functional biodiversity; (iv) the numerous terms of similar intention, definition, and intention to refined wilding and functional biodiversity; (v) improved definition of functional biodiversity and refined wilding as a conceptual frame and sorting and categorising method for literature reviews. The three literature reviews provide an opportunity to use refined wilding and functional biodiversity as an analytical framing, or schema, which further verifies the relevance and ability of the concept and grounded theory for the urban landscape to organise specific advanced interdisciplinary findings into a comprehensive conceptual framework and grounded theory. This organisation furthers how it can be a guide for urban development strategies and for urban landscape design, including specific guidance for PTSG and taxa selections, by distributed ecological function across systems and landscapes, and human and natural environment impacts that can address economic benefits. Specific examples from the literature review results are presented in

Table 10. Significant points from three literature reviews used.

Significant Points
Functional biodiversity is a rarely used term for urban landscapes as per published articles reviewed.
The terms used with similar definitions or intentions can be comprehensively defined or organised by refined wilding as a concept for urban landscapes that work toward functional biodiversity.
Verifying and contextualising functional biodiversity and refined wilding for the urban landscape emphasises the opportunity for advanced function. Advanced and specific studies from different disciplinary fields must be considered for the advanced function of biodiversity for UGSs and urban landscapes.
Trends in urban development and changes in urban development, planned or unplanned, provide opportunities for functional biodiversity interventions and adaptions using refined wilding as a preventative and improvement approach toward already set sustainability goals.
There are several different types of UGSs. Gardens, forests, urban agriculture, urban parks, meadows, residential yards, grassy lawns, green roofs, and rain gardens [19].
UGSs provide a significant opportunity for improved sustainability outcomes in urban landscapes. A landscape type that has a significant influence on economic, environmental, and societal outcomes and that requires maintained improvement. Urban grey spaces require almost the same consideration and both are reciprocally influential to blue spaces, aerobiomes, and air quality (sound, sight, climate). Refined wilding can achieve a balance in function across all UST, aerobiomes, and other aspects of air quality as a matter of adequately reaching advanced interdisciplinary studies as relevant for each particular UGS and urban landscape.
Native systems are also more conducive and acceptable to ecological function while leading to self-maintained or low-maintenance systems. They must, however, be designed for urban landscapes to ensure the functionality of biodiversity.
Human health in an urban environment can emphasise some negative aspects of urban biodiverse systems and landscapes, including pollen count and taxonomy groups of wildlife, reptiles, and insects. Design can address these drawbacks, with examples of plant selections that are non-allergenic, how pollen exposure is influenced by pollen seasons, which can be extended by combinations of non-natives and natives, and layers in UGSs that provide various functions, including noise and air filtration, alongside the complexity of the ecological function of the modified natural environment system.
UGS with multi-layered vegetation and tree canopy of non-allergenic native and non-native selections that have a limited pollen season.
Wild plants, as native or indigenous by definitional terms, are already recognised as significant for urban biodiversity outcomes but must be functional for the human population as well as for the natural environment and for ecological function.
Meadows and native grasses can address human health impacts of pollen in urban landscapes as advanced function systems.
Human populations must adapt some behaviours and interactions for the function of the natural environment.
The size, type, quality, and capacity of UGS affect visit volume and frequency [26,27] and are relevant to users of public green spaces but are determined by the designer and urban planner in most cases, with the exception of spontaneous green spaces. A residential garden is not included in these statistics for accessibility. While UGSA is limited by spatial equity, with higher-income countries having better access compared to cities in low-income countries [26] the quality of UGS by income of city or country could be measured to balance and further qualify the finding. The quality of UGS [28] can significantly influence human health, and access can improve human health, but it is not essential. UGSA, may be as significant as the quality of UGS. Physical activity without green spaces can maintain human health in lower socioeconomic urban landscapes that have lower accessibility.
Selections of natives and non-natives must be functional for ecological conditions in the system and across systems and must factor in human health, pollen season length, and allergenic selections.
Wildlife integrated into an urban landscape requires system and landscape connectivity, and human and wildlife safety considerations.
Techniques for maintenance are significant for functional biodiversity outcomes.
Native and diverse UGSs are often found to be low maintenance and sustainable, but function is not assumed.
Designing for ecological connectivity within and between systems and across urban landscapes can factor in the safety of wildlife and human interactions while providing habitat, forage, and corridors for travelling between natural environments without human exposure.
Design that ensures functional structures for native PTSG provides human control and cues for care that encourage long-term functional biodiversity outcomes.
Design by selection and distribution in any green urban space is an essential consideration for function.
An example of the novelty of refined wilding is how it can improve an understanding of spontaneous urban greenery, which is often resisted by preference but presents a significant opportunity for functional biodiversity in an urban landscape.
Refined wilding design approaches and functional biodiversity can integrate and maintain spontaneous urban greenery and informal UGS with the encouraged understanding of the greenery as native with decreased need for maintenance and with ecological functions.
Introduce and abide by regulations for planting and maintaining allergenic versus non-allergenic plants in urban landscapes.

,

Table 11. Refined wilding conceptual and design for existing and accepted sustainable practices for UGSs.

Some Commonly Understood and Practiced Aspects of Sustainable UGS	How Refined Wilding Addresses Each of the Existing Practices
Native or indigenous plants	Functional native and non-native selections assembled for a natural system function and function for human populations.
Water regulation	Selections of grasses and location of UGS; advanced design by PTSG selections and soil patterns; functional integration of UGS with built environment and infrastructure.
Air quality	Stratification and PTSG selections determined by design for functional ecological complexity and UGS type.
Low pollen	PTSG selections and functional native and non-native selections for limited pollen season.
Low maintenance	Semi-natural or natural ecological systems determined by wild PTSG selections and design for function.
Ecological connectivity between UGS, particularly community gardens	Ecological urban corridors; multi-function of ecological urban corridors for wildlife, different taxa, water regulation, and air quality; increases in UGS quality and number; improvements in informal UGS; increases in UGS in built environments, outdoor and indoor, rooftop, walls, indoors.
Wildlife habitat, forage, and transit	PTSG selections and design for habitat dependent on UGS type. Provision of a concept and design system that can provide aesthetic and built environment preferences and requirements while accommodating wildlife-friendly requirements and strategies. Integrated considerations of wildlife function as mammals and pollinators.
Limited preference for spontaneous urban greenery and informal UGSs	Conceptual guidance and design approach that can improve understanding of how spontaneous greenery and informal urban greenery can be integrated for aesthetic and safety preferences.
Meadowscaping	Refined wilding encourages wild PTSG selections and encourages selections that are low allergenic, functional, and conducive to meadowscaping; lower maintenance but different aesthetics. Plants can provide wildlife-friendly residential gardens more than grasses.
Anthropogenic assemblages	ESHR-aligned and refined wilding design as selections and spatial distributions at system and landscape level.
Diversity of taxa	Ecological function and complexity as associated with PTSG selections and spatial distributions.
Multi-layered vegetation; stratification; tree canopy	Ecological complexity by structures, vertical and horizontal of a system and landscape. Inclusion of plants, trees, shrubs, and/or grasses as functional inclusions by ESHR definition of functional biodiversity.
Microhabitats	Ecological niches [46].

,

Table 12. Advanced functional design for lowered pollen exposure risk.

Summarised Points for Advanced Functional Design for UGS That Accommodate Pollen Exposure Risks to Human Health.

Lower air pollutants during pollen season. Limit pollen season using functional and coordinated PTSG selections. Select pollinator-dependent selection and design of UGS which adequately maintain these diversities and populations. Use non-allergenic and diverse PTSG in UGS [60] Effective monitoring and communication of pollen counts and concentrations combined with air pollutants can inform UGS redesign and/or behaviour change [58,59,64]. For behaviour change: Increase visitation to parks and forests as compared to green roofs or other UGS types that might not have multiple functions. Increase visitation to UGS with non-allergenic and diverse PTSG during pollen season or when air pollutants are significant. Decrease visitation to UGS that are allergenic during pollen season. Decrease visitation during high air pollutant days/weeks/months when pollen exposure risk is high. Ecological connectivity between UGS with these functional attributes is maintained. As pollen exposure risk is publicly available, make safe UGS according to pollen seasons and exposure risk publicly available.

and

Table 13. Advanced function by refined wilding design for wildlife-friendly urban landscapes.

Summarised Points for Refined Wilding Design for UGS That Accommodate Wildlife Friendly Strategies for Advanced Function

Provide various habitat types, forage, and/or transport corridors for different wildlife types. Health considerations that can be designed for: Disease contracted from wildlife; Attacks from either a human or wildlife; Attracting wildlife to locations that are safe for reasons of traffic, electricity lines, or other examples. Landscape-level connectivity considerations UGSs connect and contribute adequately to an ecological continuity that is functional for wildlife activity in an urban landscape. Consideration of outskirt urban systems and landscapes, including roads and public transport infrastructure, which can be addressed with biological corridors that provide transit and transport as well as habitat for different wildlife. In built-up urban landscapes, these considerations are different from biological corridors between natural environment landscapes. Road or public transport infrastructure, again different by UGS type, garden as compared to forest. Complementary to the specific points for air quality and pollen exposures in Table 11, where wildlife includes pollinators, design approaches for an urban landscape that integrates wildlife-friendly strategies and provides additional consideration for advanced function for biodiverse urban landscapes. Larson et al. [50] emphasise residential gardens as significant opportunities to provide habitat for wildlife. Van Helden et al. [51] discuss wildlife-friendly gardens. Hwang and Jain [52] encourage landscape design for wildlife consideration.

. Table 10 and Table 11 provide significant points that can easily be encapsulated within the refined wilding concept and will advance functional biodiversity outcomes.

Table 12 provides an example of advanced study findings, including air quality and pollen exposure associated with human health risks. PTSG selections will determine the risk of pollen exposure presented by different UGS systems and urban landscapes and are a significant consideration for the advanced function of biodiversity in a UGS. The summarised points are related to pollen exposures and lowering risks, addressing a deterred preference for UGSs due to an understanding of human health impacts.

Table 13 provides summarised points relevant to wildlife-friendly strategies for urban landscapes that provide examples of landscape connectivity and system-level functions that reach the specific points made in Table 12 and that connect to points made in Table 10 and Table 11.

Refined wilding and functional biodiversity for an urban landscape could further specify and organise an existing extensive and interdisciplinary range of practice and knowledge for sustainable urban development. Functional biodiversity achieved using refined wilding can address the different UGS types (literature review I), indicating an ability to optimise functional biodiversity outcomes at a smaller UGS scale, particularly where informed by findings from advanced studies and selective coding and categorising from search term results lists (literature review II and III). As ESHR definitions of functional biodiversity encourage landscape connectivity across UST, these concepts can reach and encapsulate search terms, studies, and different UGS, as found in the three literature reviews. Smaller-scale refined wilding can easily reach an urban landscape level, where applied to several UGS with landscape function applied to urban grey and transparent spaces by influential flows.

Search results with design are more specific and it is, therefore, in design that specific recommendations and comprehensive guidance that integrates different advanced studies are encouraged. Design approaches that address and adapt significant points in Table 9, Table 10, Table 11 and Table 12 to different UGS types and location-specific requirements are expected to provide advanced functional biodiversity for different UGS and urban landscapes. They provide an in-depth example of how interdisciplinary studies, when comprehensively represented in refined wilding design for functional biodiversity, could improve the advanced function of different UGS types.

Adequate responses to specific recommendations from Table 10, Table 11, Table 12 and Table 13 are expected to optimise and achieve advanced functional biodiversity for an urban landscape.

4. Refined Wilding as a Verified Concept for Urban Functional Biodiversity

Refined wilding and functional biodiversity is relevant and verified for the urban landscape context with (i) the ability to provide a conceptual frame for analysing literature reviews relevant to urban landscape and sustainability, (ii) proving relevance to search term results, (iii) originality in term (functional biodiversity), (iv) specificity and reach of refined wilding, (v) ability to guide design principles and approaches which could significantly advance understanding of professionals and users [56,70] and practice for sustainable urban development. Where adequately used, they are expected to increase the opportunity for optimised functional biodiversity outcomes, also referred to as advanced function. They will reach across the different UST and functionally influence and be influenced by transparent urban spaces, aerobiome, and different aspects of air and aquatic quality. An improved intervention and intention by well-defined conceptual guidance can improve implementation and outcomes by knowledge set or practice. Refined wilding design provides the realistic capability for implementation and ‘cues to care’ [21], which can increase uptake and consistent functional biodiversity in urban landscapes. Where the advanced function of UGS is the result of design using refined wilding, different UGS types will easily address pollen distributions and exposure risks, wildlife-friendly, including spontaneous plants and informal UGS in functional biodiversity outcomes, functional ecological complexities that accommodate human health and taxa diversities, and wildlife (mammals and pollinators, birds, butterflies, bees, and insects, as examples) at a functional landscape level. Functional according to functional biodiversity is substantiated by the ESHR [22]. Further studies about UGS by number, quality, and location are required for different cities and countries and how they functionally connect across an urban landscape to ensure adequate and advanced function assessments, and improved strategies and plans for already set sustainability goals. Advanced functions for UGS can easily address and encourage a consistent and significant achievement for urban landscapes. It also encourages consideration of connectivity between urban and surrounding landscapes.

Refined wilding is verified as a substantiating concept for functional biodiversity in urban landscapes. A concept that can guide visions, strategies, and goals for UGSs and/or all USTs that can integrate green spaces or be influenced by them toward a functionally connected and biodiverse urban matrix. The methodology verifies that functional biodiversity and refined wilding can reach or support most of the specific concerns and recommendations for addressing them. It can also (i) complement or even improve upon existing terms that intend to address these concerns and (ii) encourage a comprehensive planning, design and implementation strategy which can address the interdisciplinary range of main concerns [23]. The more significant recommendations and studies that align and encourage refined wilding and functional biodiversity are (i) indigenous plant diversity, (ii) multi-layered vegetation, (iii) microhabitats, (iv) tree canopy, (v) wildlife-friendly urban landscapes, (vi) limiting pollen exposure risk, and (vii) improving the natural regulation (air, water) effects of UGSs. Refined wilding furthers these initially important aspects and complements existing terms of similar intention. It introduces a term for variably wild UGS that are for appearance and purpose precise and include native PTSG selections and functional native and non-native selections. These selections accommodate taxa diversities and for advanced function address these various advanced functions for human health, stratification, wildlife-friendly, positive influential flows between UGS, and between UGS and grey and transparent spaces (air and aquatic). The studies provided and associated terms, for example, how refined wilding can provide an overarching concept that is easily inclusive of most existing terms of similar intention. These terms are of similar general sustainability level outcomes and meaning, and are from different disciplinary backgrounds. They can easily encourage and improve refined wilding and eventual functional biodiversity outcomes as defined and implemented and provide an opportunity to precisely improve the various advanced functions that UGS can provide to an urban landscape. Native and non-native selections for any UGS encourage, as ESHR does, a system and landscape connectivity, as wild productive systems do [24]. Wild PTSG for refined wilding do, however, provide different specificity and refer to functional native or non-native selections appropriate for the local climate that are organised in a semi-natural or natural ecological system suitable for the UGS type. Pollen seasons, functional stratification, multiple functions of vegetation, and taxa diversities must be considered alongside aesthetic preferences. As a leading concept and theory, refined wilding and functional biodiversity can conceptually frame research, practice, and literature reviews and guide strategies, visions, goals and designs with integrated principles that comprehensively reach and lead most of the advanced and interdisciplinary studies. Some advanced and specific studies can also lend guidance within a refined wilding and functional biodiversity framework. In implementation, these studies and findings need to be adequately integrated into conceptual guidance and design.

4.1. Wild Refined Urban Green Spaces

There is limited expected use for wild productive systems, only determinants for urban agricultural and/or community gardens and occasionally for personal use supporting a more specific term for the urban landscape. Reference to the term functional and multi-functional is frequent. Reference to biodiversity and various types of biodiversity is, also. How these different types of biodiversity are defined and discussed tends to require specificity. These terms, when further and more specifically defined and assessed for the urban context, like agricultural wilding, which differs from rewilding by required definitional difference for different landscape types, can provide overarching guidance with the intention for improvement in urban landscapes. For this reason, wild refined UGS are introduced as a more specific outcome within the functional biodiversity theory for urban landscapes.

Refined wilding as a concept is expected to result in wild refined green spaces of advanced systems and landscape level functions. For initial use in urban landscapes, refined wilding is discussed for UGS at a smaller scale of use and can be applicable to multiple UGS, for connectivity between UGS, and for increases in UGS, particularly for built environments. Minimum proportions of native and non-native wild selections of PTSG are included for wild refined UGS as minimum proportions are provided for wild productive systems. Green, grey and transparent spaces such as aerobiome quality impacts are all considered, as well as landscape-level functions for and of UGS as a matter of functional connectivity. Urban green and grey spaces are suitable for refined wilding, with grey spaces even spontaneous greenery able to be optimised. Urban spaces and landscapes that are optimised using refined wilding are referred to as wild refined UGS. Urban grey spaces with greenery or planned increases of greenery will also be referred to as wild refined UGS. Wild refined UGS and urban landscapes will (i) mitigate the risks that some green urban spaces present for human health, (ii) ensure complexity in functional biodiversity that includes various taxa and provide functional connectivity of complexity across an urban landscape and all UGS, while addressing relevant human realities, (iii) ensure that refined wilding design is specific to the city and location and is informed by local studies and knowledge sets, (iv) work toward increases and improvements in UGS, particularly for changing urban landscapes, (v) provide functionally biodiverse UGS that optimises and does not degrade human health, (vi) functionally connect to, influence, and be influenced by other UGS, transparent spaces, of aerobiomes, air qualities, and blue aquatic qualities across an urban landscape. Refined wilding will, therefore, work toward wild refined UGS and functional biodiversity at a landscape level.

Wild refined green and grey spaces are integrated systems of diverse and functional PTSG selections (native and non-native), which are spatially distributed for semi-natural ecological systems and landscape function. They are low maintenance and of various complex stratifications and structures and variably include all PTSG, while being ecologically functional and functional for human populations. They accommodate human realities of preference, safety, and health and can improve how spontaneous green spaces are used and maintained. They are capable of achieving all aspects of conservation in an urban landscape through achieving functional biodiversity as a positive outcome for urban landscapes. Functional connectivity across wild refined UGS of various types is an expected outcome, with a balance between ecological complexities of PTSG selections conducive to maintenance and uses that maintain taxa diversities and accommodate the significant human realities by safety, human health, and accessibility to PTSG selections, aesthetic preferences, education, and capability for safe implementation and use. It can also accommodate the various complexities of ecological function, urban landscape, and human health function that different UGS types have. Eventually, every significant point can lead to complex advanced functions that the ESHR and refined wilding can reach. Specific suggestions for advanced function include human behaviour change [58] to accommodate the various human realities of urban landscapes and an ability to design and maintain functionally biodiverse urban landscapes and/or UGS.

The term differentiates between a wild natural system with no human modification versus a natural environment that is significantly modified by human populations. A wild refined urban system is closer to natural or semi-natural ecological function with continuity across a landscape that is functional for human populations and for ecological function, thus providing functional biodiversity for urban landscapes of optimal biodiversity and function by system and across a landscape.

4.2. Refined Wilding Design for Advanced Function

Design systems for urban landscapes are understood as improving an ability for cues to care [21], also referred to as anthropogenic assemblages [49] of native or indigenous plants in an urban landscape. These assemblages are referred to as design approaches that determine PTSG selections, abundances, and their distributions at a system and landscape level, with diversities and stratifications often referred to in ecological science. Functional biodiversity at a landscape level can be planned and designed for between urban and outer-urban landscapes for an ecological and functional continuity, with these examples proving existing use and knowledge of benefit as a transfer of knowledge to practice [46]. ESHR aligned design approaches [46] for an urban landscape are defined as refined wilding design. ESHR and refined wilding design considerations are where additional or advanced function considerations and questions commence, as they can comprehensively organise and integrate advanced findings for function. As a design system, refined wilding determines PTSG selections, abundances, and distributions. Ecological function encouraged with the inclusion of wild PTSG is an important basis within a system, in and between UGS systems and across a landscape. It is relevant to UGS that are productive for various reasons or are for aesthetic residential, recreational, or other public or private functions and purposes. It can result in wild productive systems or wild refined UGS and urban landscapes that are partly productive, partly for standard urban purposes, while satisfying advanced functions for urban landscapes. For design approaches, refined wilding focuses on advanced functions that specifically address the quality of UGS and their influence on other urban spaces. Quality is a balance between ecological sensitivity and addressing human realities, which include health, safety, and cues for care, and maintenance requirements and capabilities. This is different from agricultural landscapes and agricultural wilding, which is rewilding for agricultural landscapes, which addresses a need for wild plants and crops in agricultural landscapes as a contribution to functional biodiversity outcomes. The resulting agricultural systems are wild productive systems that are, first and foremost, for productive purposes with additional uses and benefits such as visitors, recreation around such systems, and populations living in these landscapes. This is as compared to refined wilding, which intends to achieve functional biodiversity with wild PTSG, which can be native or non-native but must be functional and address most of the advanced concerns and recommendations for an urban landscape.

Refined wilding avoids assumptions of any green or grey space of any native PTSG being functional or sustainable and encourages inclusion and integration of interdisciplinary and advanced study findings for advanced system and landscape functional biodiversity. It can address limitations to achieving functional biodiversity in an urban landscape by adequately designing for human realities, while pushing to new acceptable and norms for aesthetics [68]. Examples in urban landscapes include how (1) spontaneous plants are understood by urban designers and users of green and grey spaces. Spontaneous or informal UGS are often referred to as weeds [35] and as aesthetically displeasing and unsafe, but they can improve the continuity and quality of green spaces [20]. (2) Aerobiomes are degraded by pollen content caused by green spaces [32,74]; diverse wild (native and even non-native) PTSG selections that are functionally assembled or designed can limit pollen season and pollen exposure risks [60]. Refined wilding design approaches can easily address these two examples to optimise the use of existing grey spaces and ensure green spaces provide positive human health benefits. It can also avoid assumptions of any green or grey space of native PTSG being functional or sustainable. The diversity in PTSG (native or non-native) included in a refined wild system is implied as a matter of ecological complexity and conditioned by a function provided with ecologically informed design. Design can initially include only one green or grey system or several, and various UGS types.

4.3. Recommendations

Advanced studies can provide concepts that might specify guidance toward functional biodiversity as a positive outcome for urban landscapes and, therefore, a direction for responsive guidance that might inform monitoring, inventories, and assessments of urban landscapes for sustainable development goals, within the refined wilding concept as a substantiating concept for functional biodiversity. They might also provide measures that improve understanding of an urban landscape or UGS for appropriate response.

Search term results supported by literature review I, II, and III, lead to recommendations for advanced functions of UGSs and urban landscapes. The terms included in the search results as relevant improve the representation of the reach of the concept of refined wilding for the urban landscape as relevant to already used terms and studies. These search term results also prove advanced studies from ecological and medical science which substantiate and support refined wilding for functional biodiversity with specific findings and recommendations. There is, therefore, extensive and in-depth relevant knowledge from and for the urban landscape. For more advanced studies, city, country, and intercity and UGS-specific studies and adequate response from conceptual guidance and design approach for functional biodiversity should optimise positive outcomes and encourage increases in refined built environment greening, both outdoor and indoor.

Recommendations for future research and responsive urban planning are listed as follows:

• Organise the selected study findings (Table 3, Table 4 and Table 5) that provide specific and advanced considerations using refined wilding and functional biodiversity as a resource of extensive knowledge sets to improve functional biodiversity outcomes as a responsive local urban landscape and system and to UGS type.
• Use the organisation of existing knowledge sets for conceptual guidance and design approaches in urban landscapes, optimise functional biodiversity outcomes, and improve refined wilding design by ensuring locally specific and appropriate outcomes.
• Design for landscape functional biodiversity outcomes using refined wilding principles ensuring connective function between UGS types and between different USTs, including grey and transparent (aquatic and air).
• Work from methods to monitor connectivity between green spaces in cities, like the City Biodiversity Index: Connectivity of Natural Areas in a City [77] and the Singapore Index on city biodiversities, and include the additional method of measuring within-patch connectivity. These methods can determine strategies for increasing connectivity and identifying the impacts of urban development on biodiversity.
• Guide and design for the advanced function of urban green, grey, and transparent spaces for functional urban biodiversity.
• Ensure local appropriateness of any refined wilding intervention by UGS number and quality, including the allergenicity of a population [59,60,64].
• Ensure functional connectivity between UGS, different UGS types, and between different UST.
• Responsive guidance informed by interdisciplinarity and a need for specificity from different disciplines can, for a topic and practical intervention and implementation, require multi-disciplinary expertise that facilitates a vast range of understandings.
• Find and assess state of the art examples for different UGS types; Urban grey spaces that include advanced function for and from UGS, and transparent spaces that are influenced by advanced function of UGS and subsequent human health implications and benefits.

For local appropriateness, the following summarised points are presented in tables as recommendations for the advanced function of urban green and grey spaces that can ultimately advance functional biodiversity across an urban landscape. They are presented as implementation strategies,

Table 14. Implementation strategies.

Measure and understand the local landscape and individual green spaces and connect grey and transparent spaces by ecological (plant and taxa diversities) and human realities.
Design and guide for landscape connectivity and advanced function.
	Wildlife-friendly, including understanding habitat quality and importance and connectivity across an urban landscape; air quality and human health, including non-allergenic native or non-native refined wild systems with limited pollen seasons.	Human health-orientated UGS design and urban landscape design using refined wilding with consideration of transparent spaces, stratification, and ecological complexity according to UGS. Human behaviour: Ensure human health benefits by physical activity, location of UGS, and air quality benefits; Ensure quality of UGS without or with increases in the quantity of UGS.
Green spaces	Improving the quality of different UGS, types, and increasing UGS coverage and accessibility where functional biodiversity outcomes as optimal are or will be achieved,
Grey spaces	Increasing coverage and quality of green spaces on grey spaces of the built environment. Improving understanding of spontaneous greenery as a functional biodiversity aspect. Work from advanced function examples in sustainable building design, sustainable informal space design, and sustainable temporary space design and use.
Transparent (aquatic and air) spaces	Ensure the function of green and grey spaces provides a positive influence on transparent spaces, with filtrations, limiting pollutants, aerosols, and pollen exposures and improving as sensescapes and for health benefit functions.

.

5. Discussion

As refined wilding substantiates functional biodiversity for an urban landscape as a grounded theory, the terms with similar meanings indicate existing knowledge sets and practices that align with and intend similar outcomes. The advanced study outcome indicates an advanced understanding of sustainable urban development that must be taken into account. Bukvareva [9] discusses optimal biodiversity as different to high species diversity as a matter of management strategy for different UGS of different functions across an urban landscape. Functional biodiversity refers to functionality for ecological and human realities function; the ecological structures and complexities of different UGS types indicate different functions. Functional intends for function across ecological interactions and processes as well as an improved function or advanced function and by complexity in planning and design, which might lead to an increase in ecological stratification by PTSG and taxa for a UGS or across UGS types. It also intends for a landscape level function and continuity despite various functional biodiversities. With these aspects of functional biodiversity achieved, optimal biodiversity could be considered as a defined achievement as functional for the UGS type. Mata et al. [78] and Tresch et al. [49] provide examples of ecological studies that provide recommendations for functional biodiversity for UGSs. Larson et al. [50], Van Helden et al. [51], Hwang and Jain [52] and provide examples of wildlife conservation considerations for urban landscapes, which are influenced by landscape ecology. Nguyen et al. [29] and Kabisch et al. [57] provide health study findings about pollen that indicate the importance of UGS function for human health. Where these findings are adequately addressed, UGSs can lead to advanced function, limited maintenance, ecological complexity and function by taxa, and maintained or improved human health. They improve refined wilding guidance and functional biodiversity outcomes with specific disciplinary findings, presented and considered with other studies of different disciplines. UGS with non-native and native selections can suit novel urban ecosystems [14,15,16], novel landscape designs, ecological connectivity [48], wildlife-friendly [50,51,52] requirements, and meadowscaping [50] rather than high-maintenance lawns in residential or public gardens, and high air quality [32] by being a lowered causal factor for pollen exposure risk [57,64,74]. The examples of terms and concepts that can inform and even improve how UGS, including forests, gardens, roofs, walls, and agricultural systems, provide functional biodiversity across urban landscapes are examples of how refined wilding can provide an overarching concept that is easily inclusive of most existing terms of similar intention, and advanced findings from different disciplines. These terms are of similar general sustainability level outcomes and meaning, and are from different disciplinary backgrounds. They can easily encourage and improve refined wilding and eventual outcomes as defined and implemented and provide an opportunity to precisely improve the various advanced functions that UGS can provide to an urban landscape. Existing terms encourage important aspects of functional green spaces. They indicate required improvements in how grey spaces are understood and used and how landscape connectivity can improve for advanced function at an urban landscape level.

Refined wilding provides an analytical framing for determining if the greenery in a UGS is functional and high quality; this analysis can be informed by inventories from ecological studies [79] and classification and mapping of and for ecological values [79], with multidimensional values of urban ecosystems providing basis and reason for improving function and even working toward advanced function. Working from studies of UGS types, numbers and accessibility for each city is recommended for landscape-level functional biodiversity. It can also be informed by monitoring of air [57] and water quality [2,25] as influenced by UGS quality, and human health by interaction and access with different UGS types. This basis for planning, strategies, and design can better inform the eventual value of an urban landscape, including monetary values [9] Examples of the proceeding include making grey spaces green and grey with refined wilding to encourage the continuity of advanced function across a landscape. This is recommended for high-density cities [80], shrinking cities [39,40,41] that are undergoing changes and rearrangements, and for urban landscapes that experience significant urban heat or flooding [8,20,78,81]. Wild plants in urban landscapes often pertain to spontaneous, informal or weed-like green systems, which can be refined for function rather than undervalued [35,67]. Their natural ecological systems, in most cases, do require refinement, and refining provides an opportunity to increase ecological and human function with assemblages of diverse wild PTSG. Wild refined UGSs will result, and, where adequately implemented across urban landscapes by organising advanced studies and state-of-the-art, can provide an ecological function that can mitigate or improve outcomes for the human population in terms of health, living standards, and economic benefits and provide an opportunity for urban landscapes to progress to positive outcomes. Often negative impacts that other landscape types experience from urban development are expected to improve. These systems result in functional biodiversity, which optimises sustainable outcomes and improves planners’ and designers’ understanding of advanced functions for UGS and urban landscapes. Wild PTSG for refined wilding provide different specificities and refer to functional native or non-native selections appropriate for the local climate that are organised in a semi-natural or natural ecological system suitable for the UGS type. Design and strategies for implementation according to UGS type and landscape specifics, alongside grey and transparent space specifics, will further determine wild PTSG selections, spatial distributions, and advanced ecological function, and function for human populations

Existing studies reviewed in the literature verify and improve how refined wilding and functional biodiversity are relevant, contextualised, and can be implemented for urban landscapes. Some studies suggest an essential function of UGS and their number and accessibility across an urban landscape for human health. PTSG selection, by native and non-native selections, allergenic properties, referred to as allergenic potential [57,59,69], filtration properties for water or air, and function for fauna, insects, and pollinators as wildlife, has implications for human realities and are significant considerations. In some cases, accessibility is understood as associated with the quantity of UGS and the quality of UGS can receive a lower importance than is needed. There is a significant need for advanced study findings to be considered in a balanced manner to ensure that specific findings are adequately represented amongst all advanced interdisciplinary findings. Where these advanced interdisciplinary findings are integrated into guidance and implementation and where different UST, grey (informal, spontaneous, and built environment) and transparent spaces are integrated as influential to outcomes, the advanced function of urban biodiversity at the system and landscape level is expected.

Refined wilding substantiates functional biodiversity as a positive outcome for urban landscapes, with the ESHR providing a definition for functional biodiversity [22]. As conceptual guidance for HNEI, a range of interdisciplinary and specific findings from advanced studies can lead to UGS and urban landscapes achieving an advanced function. It can encourage advanced consideration of how ecological interactions and processes are interdependent on human realities and how human inputs require sensitivity to the natural environment. Functional biodiversity outcomes from refined wilding complement the concept and implementation of nature-based solutions, novel urban ecosystems [14,15] and renaturing. Renaturing is an outcome of nature-based solutions [8,81] and is defined next to rewilding and urban rewilding. Refined wilding develops from agricultural wilding, a term developed using grounded theory for rewilding in agricultural landscapes [24]. It further specifies and defines a rewilding for the urban landscape and substantiates functional biodiversity outcomes for urban landscapes. It is a complementary term for nature-based solutions and renaturing, which is an urban landscape-specific term used to respond to challenges like floods and urban heat islands [20] but is not limited to response to challenges. The complementary aspects of refined wilding and functional biodiversity might further assist and guide the recommendation and opportunity for landscape architecture’s contribution to improving the use of terms for improved urban sustainability outcomes. Refined wilding toward functional biodiversity can guide urban development strategies and design for implementation. It can, therefore, provide cues for care at the system or landscape level for preventative and advanced function use and is recommended for any UGS type and urban landscape. The quality of UGS is recommended over the quantity of UGS, for reasons of advanced function. Advanced functional biodiversity across an urban landscape by refined wilding for various UGS types is more likely to achieve targeted, sustainable development goals for urban development. Optimised biodiversity [19] as an advanced function of biodiversity is also considered an indication of UGS quality where a UGS is designed for multiple functions responsive to local landscape conditions and optimised according to the concept and theory. This optimised biodiversity will provide functional connectivity between all UST, increase UGS across urban grey spaces, and functionally connect urban landscapes with neighbouring landscapes and systems. It is expected to maintain and improve human health and the natural environment, and provide functional connectivity between countries. Implementing refined wilding for functional biodiversity outcomes using the concept for guidance for various strategies, visions, and policies for urban development and for design is expected to result in outcomes that are responsive to interdisciplinary studies and connectivity across different UST. The expected improvement in urban functional biodiversity outcomes for most UGS types will encourage connectivity across an urban landscape conducive to landscape-level functional biodiversity outcomes.

With this basis of information, guiding strategies, visions, and goals with refined wilding as an organising concept and functional biodiversity as a desired outcome could increase and improve urban landscapes for advanced functional biodiversity. The positive outcome of functional biodiversity can also initially be led by a different focal point. Health is an example where the negative impacts of UGS on human health can be prevented, and positive impacts can be increased with refined wilding design for functional biodiversity. It must work from an accurate understanding of UGS types, quality, and accessibility across an urban landscape, including inventories, pollen counts, and exposures. From here, from the advanced studies in the results, urban planning and strategies can be informed by the number of as compared to the quality of UGS, and accessibility as compared to high quality. Low-quality UGS can degrade health by allergenic PTSG selections that increase the risk of pollen exposure; high-quality UGS can regulate air quality and limit pollen exposure. Functional native and non-native non-allergenic selections that are functionally assembled can address these human health factors for indoor and outdoor environments. The design concept and desired positive outcome, functional biodiversity, can also encourage and then result from a health focus that eventuates to an advanced function. Further consideration can include how behaviour change can avoid pollen exposure risk where changing a UGS design to lower allergenicity requires inaccessible resources. Refined wilding, in most cases, will lead to a low maintenance system, which limits the need for the capability of a user but increases how the capability of a designer and implementer is needed. UGS, particularly urban forests and community gardens, also provide additional health benefits which could be negated without the advanced function of mitigated pollen exposures. These benefits include sense scapes, as therapeutic, sounds, sights, and scents are proven to improve health, hypertension, and mental health [32]. Pollen exposure in already polluted air can worsen mental health [33] and increase the risk of respiratory disease. Additional examples which would be considered by this health-led example are wildlife-friendly and the use of aquatic and built environments for functional biodiversity and different UGS types, depending on the urban landscape context. These additional focal points provide examples of how functional biodiversity and refined wilding as supported or defined by ESHR, provide an opportunity to bring terms and advanced study findings from different disciplinary fields or different categories tougher for improved functional and advanced sustainability outcomes.

Design guided by refined wilding for functional biodiversity in urban landscapes will improve how biodiversity can address sustainability intentions and how significantly influential a human population is. It can (i) encourage what is recognised as a needed increase in native selections in residential and urban gardens for improved functional biodiversity outcomes; (ii) consider the complexity needed in ecological interactions and processes; (iii) allow complexity in vegetation, even multiple layers which are extremely conducive to providing urban biodiversity and taxa diversities that rely on wild (native and non-native) PTSG for food [56]; (iv) ensure a functional balance of native and non-native plant selections for advanced function. It, therefore, ensures that UGS systems and connectivity between different urban spaces are functional and coordinated; (v) provides an advanced function for human health through strategic selections of non-allergenic pollinator-dependent PTSG; (v) provides ecological conditions for a variety of fauna and pollinators while accommodating human safety and health effects for the urban landscape. Where integrated and organised, and advanced study findings inform design approaches, an advanced contextually specific and appropriate functional biodiversity in urban landscapes is more expected. Refined wilding design, as a new term, can equally and adequately provide a framework for advanced interdisciplinary findings with designs that are landscape-specific and responsive to individual urban landscape needs.

The value of refined wilding and functional biodiversity for the urban landscape is shown through trends in urban development and how these landscape changes provide opportunities for improvement. As landscapes with high proportions of human populations and significantly negative environmental impacts, these changes are significant. Emerging urban landscape trends met with responsive strategies, visions, and policies that encourage or require refined wilding design for advanced function across an urban landscape are likely to provide functional biodiversity for urban landscapes that reach every aspect of influence that a UGS has as per sustainability definitions and principles. Moreover, at a time when adaption and change could result in decreases in sustainability performance, it integrates aspects that advanced and interdisciplinary studies or original observations indicate as significant in terms of an urban landscape’s ability to achieve advanced practices, concepts, and advice from each disciplinary field. As advanced function addresses human health, it is recommended that refined wilding landscape design and functional biodiversity influence [71] and follow regulations, find a balance between recommending UGSs for health while ensuring advanced function, adapt or find a balance between behaviour and aesthetic preferences where possible, and ensure functional connectivity between all urban green, grey, and transparent spaces, aerobiomes, and other aspects of air quality [59], publicly list UGS that are low risk at different times of the year and adapt human behaviour. The more advanced and coordinated study findings are within a refined wilding conceptual framework and design approach, the more advanced the implemented strategies and visions for UGS and landscape connectivity.

Recommendations and implementation strategies provided in explanations of refined wilding and functional biodiversity for advanced function offer further guidance for urban development trends. Eventually, a wild refined UGS and landscape will have a functional connectivity between UGS and positive influential flows with grey and transparent spaces. These UGS will be functionally diverse and biodiverse and are not only for productive function. The intention of functional native and non-native selections for any UGS encourages, as ESHR and wild productive systems do, system and landscape connectivity [22,23]. The concept and theory are expected to provide consistent guidance that can encourage initial monitoring to determine and ensure responsive strategies, plans, visions, and design for an urban landscape or for a UGS influential to urban grey and transparent spaces.

6. Conclusions

For the urban landscape, the main concern [23] is degrading the environment and the two other categories of sustainability, society and economy. Researchers and disciplinary experts hold expertise and understanding that further verify this concern and provide recommendations for urban landscapes.

Refined wilding, as a new term and specific conceptual approach, substantiates functional biodiversity for the urban landscape, as agricultural wilding [24] does for the agricultural landscape. This specificity can ensure that functionality for humans and the natural-environment is accommodated and that the term rewilding is not used outside of its original definition, which is to rewild with keystone species, different than taxa and wildlife and PTSG selections, which are often complementary strategies and not for urban landscapes [21,29]. It encapsulates or improves specificity while reaching and refining existing and agreed-upon good practices or state-of-the-art terms and discussions for urban landscapes. In some cases, the existing practices, terms, and advancing discussions for practice can further the specificity of refined wilding and functional biodiversity-led strategies and visions for different urban landscapes. It is suggested as a term that could optimise the various types of UGS for functional biodiversity outcomes by reaching and requiring balance among various relevant disciplinary studies and UGS purposes. Health as a guiding point for functional analysis using refined wilding and functional biodiversity can encourage a functional connection and balance between human beings and the natural environment. The user of the concept will determine how it can achieve this balanced and advanced function.

Advanced function is a significant opportunity to develop and adapt urban landscapes efficiently while optimising sustainability outcomes. Ensuring functionality in any wilding depends on the landscape type and further classification by a semi-natural or natural ecosystem that reaches landscape functional connectivity. The reach will be across green, grey, and transparent spaces and influential to and influenced by the aerobiome and aspects of air and aquatic quality. Advanced function for UGS would ensure functional biodiversity by refined wilding, which reaches all significant advanced findings and consistently includes grey and transparent space influences.

Refined wilding intends functional biodiversity outcomes for the urban landscape and for any UGS by integrating a diverse and functional range of wild PTSG, and, occasionally, crops (native and non-native) with advanced functional biodiversity considerations that can address and reach a functional connection between humans and the natural environment while ensuring ecological function and connectivity across a landscape. A refined wilding and functionally biodiverse UGS does not have to have every PTSG. However, more complex systems will support more diverse taxa and ecological function that normally requires less maintenance, and design will ensure the function. By definition, refined wilding for functionally biodiverse green spaces includes a functional selection of wild crops and PTSG (native and non-native) and intends to refine green, informal and spontaneous and grey urban spaces [20] for functional biodiversity outcomes. It provides a wild refined semi-natural or natural green and urban system that satisfies the expectation of the standard and advanced function of any type of green space. The functions of these wild refined green spaces are expected to assist in protecting and even improving transparent spaces. The definition of wild for agricultural wilding [24] includes functional selections of native and non-native PTSG that take pollen seasons, taxa communities, safety, human health, and aesthetic preference into account. For agricultural wilding [24], wild crops and plants are defined as non-domesticated and growing in a productive system. They can grow spontaneously in self-maintaining populations and in natural or semi-natural ecosystems that can exist independently of direct human action. As refined wilding is a substantiating concept for functional biodiversity in urban landscapes, it is informed and substantiated by the ESHR. The ESHR allows consideration of a range of aspects of ecological conditions and human realities. Where these considerations are adequately understood and acted upon, an advanced function of green spaces, and eventually transparent spaces and aerobiome and air and aquatic ecosystem quality are expected. Urban agricultural systems are the UGS type most likely to use wild productive systems, and agricultural wilding, all the other UGS types, thirteen types, can achieve functional biodiversity with refined wilding and with functional selections of wild PTSG.

These integrated considerations, as encouraged by ESHR, address every aspect of ecological interactions and processes, and human realities, particularly human health. The wild native and non-native selections of PTSG for any UGS and the structure by configuration and composition must be functional not only for the natural-environment but for human health and the economy. The integration and consideration of PTSG selections and their configuration and composition, which in ecological terms can encourage functional interactions and processes for microhabitats using ecological niches [46], taxonomically diverse communities, and wildlife-friendly, leading to function for human populations, and for a urban space system, and for the urban landscape. Function for human populations encourages consideration of realities of an urban landscape, UGS access, health, access to PTSG selections, maintenance requirements, capabilities in design and use, aesthetic preferences, and limited productive functions. How these functions are adequately balanced by functional biodiversity outcomes can address various negative developments in urban landscapes. In some cases, functional biodiversity is more achieved; in other cases, it can address air, water, and soil quality and for example improve human health and in turn economic, environmental, and other societal factors.

For refined wilding, wild PTSG are assembled in semi-natural or natural systems for urban landscapes as functionally biodiverse green systems. These systems are of various uses and types, and have variable functional ecological complexities and other functions. They do not all have productive intentions, can satisfy aesthetic preferences, and have variable complexity. They are referred to as refined as, and in most cases, an urban natural environment system will not be a naturally wild system. The majority are human-modified for the urban landscape.

Wild PTSG selections are diverse and functional to require low maintenance, limiting the proven negative effect of intensively managed green [24] spaces. Wild refined green and grey spaces composed of native and non-native selections, with diverse and complex structures, of PTSG and taxa improve ecological function. The other functions must address human realities, including human health and influence on transparent spaces and aerobiome, air and aquatic ecosystem quality. How they satisfy all functions determines how advanced their function as biodiversity in urban landscapes is. Refined wilding, therefore, infers a functionally biodiverse urban landscape that comprises native and non-native, wild flora and fauna, and pollinators and insects, and provides a natural or semi-natural system that can self-regulate and improve or maintain human health. It can assist to counteract the effects of various urban development trends and their detrimental environmental and societal outcomes, and ensure that UGSs do not contribute to decreases in human health status. In urban landscapes, these sustainability intentions are already by various different terms and are variably understood. Diversity, native selections, and ecological continuity across an urban landscape are already often referred to as positive outcomes.

Refined wilding can provide guidance for changes in urban landscapes and responsive strategies, visions, and goals for urban development, particularly for UGS, and lead to more advanced positive outcomes. There is limited use of the term functional biodiversity and variable definitions for the urban landscape. Existing terms (literature review I) and studies (literature review II) evidence a long-standing and extensive knowledge set of research and practice, with newer topics for research evident. These knowledge sets improve sustainable urban development. The fact that refined wilding and functional biodiversity can reach these terms and knowledge sets and improve integrated understandings and be improved by them indicates an ability to provide adequate design approaches, principles, and guidance for optimised functional biodiversity in urban landscapes while proving the relevance of both terms for the urban landscape. Refined wilding design is influenced by and responsive to a balance of advanced study findings according to UGS type and the urban landscape context and facilitates locally appropriate implementation. It will result in wild refined UGSs that functionally connect to grey and transparent spaces, particularly air quality [32], and aquatic ecosystems [25]. The concept and theory can provide the same guidance for strategies, visions, and goals for sustainable urban development at the system and landscape level. Recommendations provide specific guidance for the use of the concept and definition of the theory, which can ensure improvements and achievement of sustainable development goals for urban landscapes that are optimised and advanced. This optimisation and advancement, which commences from environmental and social aspects, can provide efficiency by use and coordination of existing knowledge sets and planning, conducive to economic and social sustainability.