2.1. Sustainable Development and Sustainable Cities
The concept of sustainable cities comes from the theory of sustainable development. While the Industrial Revolution and the scientific and technological revolution in the 20th century promoted the rapid development of human society, they also brought about a series of environmental problems that are not conducive to the development of human society, such as the over-exploitation of resources, environmental degradation, and disorderly urban expansion. In this context, the United Nations held a Conference on the Human Environment in Stockholm, Sweden, in 1972, and the theory of sustainable development was formally discussed by the international community for the first time. The United Nations Conference on Environment and Development (UNCED) published a report named Our Common Future in 1987, which systematically explained sustainable development for the first time, defining it as a development that meets the needs of the present without compromising future generations to meet their needs. Agenda 21, adopted by the United Nations in 1990, marked the transition from theory to practice in the context of sustainable development [
4,
5]. The theory of sustainable development was introduced in China in the early 1990s. China first proposed this theory at the Conference on Ministers of Environment and Development of Developing Countries in 1991. Since then, Chinese scholars have applied the concept of sustainable development in many aspects, such as ecological environment protection, urban construction and renewal, and the protection of traditional culture.
Sustainable cities apply the concept of sustainable development to urbanization and urban construction. The purpose of sustainable cities is to solve the problems brought about by urbanization, such as environmental pollution and social inequity. “Sustainable city” was defined by the the Sustainable Cities Programme (SCP) launched by the United Nations Human Settlements Programme (UN-HABITAT) and the United Nations Environment Programme (UNEP) in the early 1990s, and was internationally agreed upon [
6]. The definition is as follows: “a sustainable city is a city that has achieved sustainable social, economic, and natural environments. The city’s use of resources and the environment is maintained at a sustainable level and has a lasting resistance to potential environmental risks”.
In 1991, the Chinese government launched the Conference on Ministers of Environment and Development of Developing Countries. The conference issued the Beijing declaration, which defined sustainable urban construction. In 1994, China formulated and promulgated China Agenda 21, which stated that the goal of sustainable cities in China is “to build cities with reasonable planning and layout. The city has perfect supporting facilities, which can provide convenient work and life. The living environment is clean, beautiful, quiet, and comfortable”.
At the macro level, the current research on sustainable cities in Chinese mainly focuses on the theory of sustainable construction, the construction of an evaluation index system, and the types of sustainable cities. The “three-pillar theory” is the most recognized concept of sustainable development in academia. Thus, Chinese scholars’ research on sustainable urban construction theory focuses on three aspects: economic, social, and ecological [
7]. When Chinese scholars conduct research on the construction of a sustainable city evaluation index system, they mainly focus on the levels of urban construction, social construction, and economic development and environmental protection [
8,
9,
10,
11]. Chinese scholars have rich research results on sustainable city types, which can be divided into three categories according to the urban development goals: research on healthy and forest cities, with the goal of improving the ecological environment; research on low-carbon and circular economy cities, with the goal of promoting urban transformation or renewal; and research on livable and ecological civilization cities, with the goal of comprehensive development [
12]. At the micro level, Chinese scholars’ research on sustainable city construction mainly focuses on infrastructure planning, design, and construction, such as studies on communities, parks, and transportation [
13,
14,
15,
16].
In summary, the sustainable city research of Chinese scholars is mostly carried out from the perspective of the government, while research on the status, role, and participation of citizens is still rare.
2.2. Environmental Literacy
In the 1960s, consumerism spread throughout American society, accelerating the predatory development of the natural environment, causing the serious pollution of forests, soil, water, and air [
17]. At that time, many scholars believed that environmental pollution was caused by those who were considered to be “environmentally illiterate”. Roth, an American scholar, proposed a concept opposed to “environmental illiterates”, i.e., environmental literacy, in 1968. To him, environmental literacy referred to the comprehensive quality of knowledge, emotions, values, skills, and actions that people have about the environment and the human–environment relationship [
3]. So far, complete agreement on the definition of environmental literacy has not been reached (see
Table 1). However, we can see that environmental literacy is not only related to the public’s environmental knowledge, values and emotions, but also closely related to their environmental protection behavior.
Personal environmental literacy can significantly influence environmental behavior and promote the emergence of their environmental behavior [
23]. Taeshina [
24] explored the impact of environmental literacy on farmers’ farmland ecological protection behavior and concluded that farmers’ environmental skills had the greatest impact on ecological protection behavior. As an important part of environmental literacy, environmental awareness can make individuals pay attention to the environment and accept related information, correctly understand and evaluate environmental problems, and consciously regulate their own behavior. That is, people with stronger natural consciousness have more environmental behaviors [
25].
The evaluation of citizens’ environmental literacy can understand the characteristics of citizens’ environmental literacy and their support for environmental behavior. In 1976, the Department of Environmental Education of South Carolina developed a preliminary evaluation index system of environmental literacy, which includes knowledge, skills, and attitudes [
26]. The research group of “the research project on Chinese public environmental literacy indicator system” divides environmental literacy into four aspects: environmental knowledge, environmental values, environmental attitude, and environmental behavior. Up to now, most environmental literacy assessments have been carried out on the basis of environmental knowledge, environmental attitude, and environmental behavior. Based on this, this paper designs an environmental literacy measurement scale including three dimensions of environmental knowledge, environmental values, and environmental behavior.
Environmental knowledge is the foundation of environmental literacy [
27]. On the composition of environmental knowledge, different scholars put forward different opinions. According to the different levels of environmental issues citizens are involved in, it can be divided into daily life, regional, and global environmental knowledge [
28]. Sun’s article [
29] divides environmental knowledge into the knowledge of environmental problems and knowledge and skills of adopting environmental behaviors. Chen and Lou [
30] believes that environmental knowledge includes knowledge understanding degree and knowledge approach. For the design of measurement items of environmental knowledge dimensions, we can use the combination of knowledge rate and accuracy rate, the Likert scale and single choice. In terms of environmental knowledge scale, the Chinese General Social Survey project (CGSS2010), which is hosted by the Department of Sociology of Renmin University of China and jointly implemented by other academic units, has formed a more authoritative environmental knowledge scale [
31] by verifying a large number of people in various provinces and cities in China.
Environmental values are important standards and norms for people to deal with the relationship between humans and the ecological environment, and their evaluation development is the most mature. Among them, the most famous and influential measurement scale is the “new ecological paradigm” (NEP) scale. This scale was proposed by Dunlap and Van Liere, and its applicability in China has been extensively tested. Hong [
32] concluded that the properly revised NEP scale can be used as an important tool to measure public concern about the environment. Yao [
33] took haze in Shanxi province as a microcosm of China’s experience and concluded that the NEP has a strong explanatory power for the microcosm. Wu and Zhu’s paper [
34] showed that the revised student version of the NEP scale had good reliability.
There are many different expressions of environmental behavior, such as environmentally friendly, pro-environmental, ecological, environmental protection, and sustainable behavior. The connotations expressed are basically the same, emphasizing the individual’s active participation and action to solve or prevent ecological environmental problems. The environmental behavior reflects the behavior subject’s respect for nature, is conducive to human survival and the development of positive pro-social behavior. In terms of the composition of environmental behavior, Hines and Hungerford [
20] divided environmental behavior into five categories: ecological management, persuasion, consumption, political behavior, and legal behavior. Stern [
35] proposed the concept of environmentally significant behaviors, which can be divided into four categories, including the environmental protection behavior of individual citizens, such as limiting automobile exhaust emissions and domestic water use, which are closely related to the daily life of the individual. Based on this, this paper carries out measurement from the dimension of daily environmental behavior and behavior frequency, such as clothing, food, housing, and transportation.
2.3. Environmental Education
Pritchard initially proposed the concept of environmental education in the establishment of the International Union for Protection of Nature and Natural Resources (IUPN) in 1948. Currently, there are three theories about the connotation of environmental education: discipline theory, process theory, and method theory (see
Table 2) [
36]. Due to changes to, and the expansion of the concept, there is still a lack of complete consensus on the definition of environmental education. However, it is widely accepted that environmental education is aimed at protecting the environment and promoting the consciousness and behavior of environmental protection by cultivating or improving people’s related knowledge, skills, attitudes, and values. In addition, previous research conducted by numerous scholars in various fields has proven that environmental education can enhance public environmental literacy and promote environmental protection behaviors [
37].
In the 21st century, the concept of sustainable development has been gradually attracting attention from all walks of life. The United Nations Conference on Environment and Development (UNCED) adopted Agenda 21, which pointed out the importance of environmental education to enhance the abilities of solving environmental problems, and also added the idea of “sustainable development” as the new connotation and target of environmental education [
38].
In conclusion, citizens who receive environmental education will grasp a stronger awareness of environment, more skills of environmental protection, deeper consciousness of the relationship between humans and nature, thus joining in protecting the environment to promote sustainable urban development.
2.4. Study on the Environmental Education Demand
This study first introduces the concept of demand before that of environment education demand. The concept of demand often appears in the fields of economics and psychology. In economics, demand refers to the consumer’s need for purchasing certain goods under a certain period of time and under certain price conditions; while in psychology, demand refers to a certain lack or imbalance in the organism, and it is mostly expressed in the form of intention, desire, motivation, interest and values in human activities [
42]. For example, in [
43], the psychologist Kurt Lewin pointed out a certain balance between the individual and the environment. If that balance was damaged, the individual would generate tension, then the demand and motivation to ease nervousness would be stimulated. So, compared with psychology, the demand in economics is also affected by external factors, such as the ability to pay, supply, and other factors. Inspired by the concept of “demand” in psychology, this paper believes that the demand for environmental education is the demand of mankind to learn about environmental knowledge and environmental skills in order to achieve a balance between man and nature and to eliminate the adverse effects of environmental problems.
Public environmental education systems consist of environmental education content and environmental education methods. The environmental education content corresponds to different educational objects in different scenes, and the content composition is different. The content of environmental education for students in schools includes environmental knowledge and ethics. In tourism activities, the content for tourists includes environmental ethics, attitudes, management technology, and knowledge [
44]. In communities, the content for residents includes environmental knowledge, skills, behaviors, and emotions [
45]. It can be concluded from the above studies that the contents of public environmental education include environmental knowledge, environmental skills, and environmental ethics according to the public’s cognition of the environment. Environmental knowledge is supposed to help people understand the objective matters and general laws of nature. Environmental skills can help people to develop behaviors of protection. Environmental ethics is to help people understand and think about the relationship between man and nature. With the development of information technology, environmental education has become more abundant. The traditional methods of environmental education mainly include school and non-school education. School environmental education is the main form of implementation in the international community at present [
46], which is mainly aimed at school students, such as the Green Ribbon Schools program in the United States and the Youth Regional Environment Program in Japan [
47]. Non-school education is represented by environmental education for the public in specific places of rural, natural, and outdoor education [
48]. With social networks and the use of mobile media subverting and substituting for the traditional ways of disseminating information, the methods and channels of environmental education are also constantly changing. The purpose of this paper is to promote environmental education for the public in Beijing, considering that there are many types of audience and various channels for receiving information, so the research on the mode of environmental education is mainly based on the study of mass media [
49].
The subsequent study on reasons for individuals’ different environmental education demand shows that individuals have different environmental education demands due to various factors, such as sociodemographic characteristics and environmental education experiences [
50]. At present, there are few studies on the factors of public environmental education demands. So, this study conducts a literature review of the influential factors about the demand for education, which is the superior concept of environmental education. The relevant literature indicates that there are mainly three types of factors affecting the demand for education: economic factors, cultural factors, and social factors [
51,
52]. The impact of economic factors on education demand is that the better the family or individual’s material conditions, the higher the individual’s need for higher-level teaching. The impact of cultural factors is that when the family or individual receives more and better education, the deeper their knowledge of education, the more they can recognize the benefits brought by education, and the higher their demand for education. The impact of social factors is that, with the complete educational resources that society can provide, like settings, teachers, etc., the education demand of an individual will increase a lot. Accordingly, the environmental education demand discussed in this study excludes environmental factors from the perspective of psychology. Therefore, this study mainly discusses the influence of cultural factors on the demand for environmental education. From the influence of cultural factors on education demand, it can be inferred that the higher the individual’s cognitive level of environmental knowledge, environmental protection skills, and the relationship between people and the environment, the higher their demand for environmental education will be. For example, Zhang Qi conducted a survey on the green lifestyle of Beijing residents and found that citizens who had a high level of awareness and practice of green lifestyles were willing to learn more about green lifestyles [
53].
In summary, the public’s awareness of environmental knowledge and environmental skills affects their demand for environmental education. Therefore, before conducting a survey on the environmental education demand of the public, it is necessary to understand their current status of environmental knowledge, environmental skills, and environmental ethics, that is, to evaluate their level of environmental literacy first.