1. Introduction
The urbanized world has brought social, economic, and environmental sustainability into increasingly challenged surroundings, which necessitate the exploration on their intertwined relationships, particularly in the rapidly rising countries [
1,
2,
3]. The urban population has increased from 2.3 billion to 3.9 billion from 1994 to 2014, indicating that more than half of the world’s population currently dwells in urban areas [
4]. At the same time, urban ecosystems and landscapes have become increasingly domesticated and vulnerable though urbanization [
5]. A series of eco-environmental problems such as resource consumption, biodiversity, climate change, and environmental degradation have emerged and sprawled [
6,
7]. In the context of rapid urbanization, cities have become the engines of socio-economic development, and resolving such problems in these highly dense urban areas requires further investigation [
8].
The relationship between urbanization and sustainability has long been the focus of numerous studies [
9]. In the recent surge of interest in sustainability, some scholars believe that urbanization is the key to regional and global sustainability, whereas others regard urban sustainability as an oxymoron [
5]. For a long time, the interaction between urbanization and sustainability is embodied in ecological sustainability, which is closely linked to ubiquitous urban sprawl and social sustainability correlated with continuous urban population growth. In an ecological sense, the past several decades have seen a widespread urban expansion in developing countries such as China and India. Such expansion has put enormous strain on its supporting ecological systems. Impervious lands such as settlements and highways have sprawled rapidly with the cost of cropland, forest, wetland, and other lands with high ecological values in urban areas. In this case, although the urban landscape has been transformed into a manageable pattern in terms of its connectivity and compactness [
10], the ecological habitat is greatly challenged because the urbanized landscape profoundly affects the related ecological processes and services [
11]. In a socio-economic sense, sustainability revolves around two core themes (
i.e., “social equity” and “economic balance”) all the way through [
11,
12]. Social inequality is associated with issues such as social welfare for rural migrants [
13], separation of peasants from their land leading to the deterritorialization of the peasantry [
14], weak social ties in the urban setting with increasing rural–urban migration [
15], and increasing health risks from air pollution, occupational hazards, and traffic injury [
16]. In its initial stage, urbanization positively affects the social aspects, including social mobilization, literacy, political participation, education, income, and health. However, these effects become negative when urbanization goes beyond the carrying capacity of the city [
17]. Economic balance mainly refers to a holistic framework for industrial development in different sectors [
18]. A number of developing countries have experienced rapid industrialization and urbanization [
19]. In recent years, the service sector, which requires a variety of manual labor, has rapidly become the leading sector in the industrial structure of many countries [
20]. Under this industrial transformation, the requirements for natural resources and energy use have expanded, thereby threatening the carrying capacity in certain areas. Consequently, economic balance is vital to achieving the harmonious development between human activities and the natural environment [
21].
In this study, Brazil, India, and China are considered “BIC” countries to be our representative study areas for investigating sustainability and urbanization. Jim O’Neill first introduced the BRIC countries—Brazil, Russia, India, and China—almost one and a half decades ago through a Global Economics Paper of the Goldman Sachs entitled “Building Better Global Economic BICs” [
22]. These countries with large geographic and demographic sizes and high economic potential have experienced unprecedented boom in socio-economic development and have occupied increasingly relevant positions in the world economy. However, a series of essential problems in this course, such as increasing socio-economic discrepancies between rural and urban areas as well as air, aquatic, and terrestrial pollution, cannot be disregarded [
23]. Distinguishable development trajectories provide characteristic references for exploring the sustainable urbanization pathways. As a result, Brazil, India, and China are chosen as the representative countries of our study to summarize the similarities and differences in the process of urbanization. Russia is excluded from such investigation because it has undergone the remarkable dissolution of the Soviet Union, and the data analysis on the urbanization of this country is inconsistent with those of other countries.
5. Sustainability in City Development
As the spatial agglomeration of production, wealth, and consumption, cities command an increasingly dominant role in the global economy. The rapid urban growth throughout the developing world is seriously outstripping the capacity of most cities to provide adequate services for their citizens. Over the next 30 years, virtually all of the world’s population growth is expected to be concentrated in urban areas in the developing world. Consequently, a sustainable urban system has been highlighted to balance city development at different levels and in different regions.
City developments in Brazil, India, and China experience different trajectories, whereas the crucial roles of large cities are the same.
Table 3 lists the number of cities in the BIC countries with populations greater than five million and in the range of one million to five million in 1990, 2000, and 2010. India and China have the most cities with populations over five million and in the range of one million to five million in 1990. In 2010, China ranks first with 14 cities with populations greater than five million and with 70 cities with populations ranging from one million to five million. The population of Brazil lags behind those of India and China, especially in medium-highly populated cities.
Table 4,
Table 5 and
Table 6 list the top 10 cities in Brazil, India, and China with the largest populations in 2010.
Most of the large cities in Brazil, such as Sao Paulo, Rio de Janeiro, Salvador, and Belo Horizonte, are located on the eastern coastal area. Many of the cities in Brazil are located on a coastline of more than 8600 km, which encompasses approximately 20% of the total Brazilian population distributed within 17 states, 395 municipalities, and 16 metropolitan regions [
35]. The abundance in natural resources in coastal zones clearly explains this intensive distribution. The urbanization in these cities is also associated with the “spreading” of the historical urban–industrial concentration in the southeast. Historically, Sao Paulo and Rio de Janeiro have become the densest and most dynamic urbanized cities with an integrated urban system in the 1950s, and this superiority remains until now. The population of Sao Paulo peaked at 11.79 million and that of Rio de Janeiro reached 6.45 million in 2014, ranking at 141 and 229, respectively, according to the Global City Competitiveness index in 2011–2012. However, the population growth rates in these megalopolises lagged behind in the past two decades. From 2010 to 2014, the population growth rate in Rio de Janeiro was 2.11%. As found in many other countries, this phenomenon was largely attributed to the economic and industrial decentralization since the 1970s. The readjustment of the regional development strategy gradually made both cities lose the momentum and stimulated the development of Belo Horizonte, Porto Alegre, and other well-equipped selective and externalities-rich areas. Since the 1990s, with the formation of Brasilia’s hinterland and the process of regional metropolization, a new socio-spatial dynamics of the Brazilian urbanization was observed in the Center-West Region [
34]. Brasilia saw a noticeable population growth from 1991 to 2010, most of which was attributed to the absorbing of an expressive contingent of northeast immigration. As a large regional center in the north, Manaus exhibited an expressive urbanization expansion and was characterized as a migrant pull center. The population of this city was slightly above one million in 1991 and even doubled at the end of 2014.
The city development in India does not show apparent spatial clustering. Three large cities—Mumbai in the west, Delhi in the north, and Kolkata in the east—with enormous populations, present the economic rewards and unique challenges in urbanization [
36]. Since 2000, the populations of all these cities have exceeded 10 million, with Mumbai peaking at 18.39 million, Delhi at 16.35 million, Kolkata at 14.06 million in 2010. The singularity of the distribution of Indian cities was caused not only by the preponderance of these megalopolises but also by the presence of a set of “secondary cities” with large populations such as Chennai, Hyderabad, Bangalore, Ahmadabad, and Pune having populations of between four million and nine million in 2010 [
37]. In the past two decades, cities in the west such as Ahmadabad, Pune, and Surat developed rapidly with a population growth rate reaching 85.1% in Surat from 1990 to 2000. Chennai, Bangalore, Hyderabad, and Ahmadabad were cities whose population growth rates were higher in 2000–2010 than those in 1990–2000. In particular, the population of Bangalore increased from 5.7 million to 8.52 million from 2000 to 2010, with a growth rate reaching 49.44%. This finding justified the statement that the region around Bangalore, in the “corridor” linking Hyderabad, Mumbai, Ahmedabad, and Delhi, experienced the most burgeoning city development. In general, city development is a two-tier hierarchy system in India, with Mumbai, Delhi, and Kolkata in the first class originating from the influence of the colonial period (the gateways to India by sea) and the rest of the cities with populations greater than five million as the second class, whose developments are promoted by endogenous urbanization over several centuries [
37].
The urban development in China demonstrates an apparent spatial heterogeneity, with the northwestern cities lagging behind the southeastern cities. Beijing (the capital city of China), Shanghai (the harbor city in the east), and Guangzhou (the city in the southern coast) are the most developed cities, with populations of 16.45 million, 20.22 million, and 10.64 million in 2010, respectively. With remarkable economic, social, cultural, and political positions, these cities have also been the ideal destination for trans-city immigration for a long time. In the past two decades, the Chinese cities in the southern part have also experienced unprecedented development in terms of their socio-economic performances. In 1990–2000, the population growth of Dongguan peaked to 600.68%, and Foshan had a high growth rate of 144.47%. As the first economic zone established after the Reform and Opening-up Policy, Shenzhen has expanded at an extraordinary pace, and its population exceeded 10 million by the end of 2010. In 2014, China adjusted its “city categorization standard,” and all the cities listed in
Table 6 are the newly defined megalopolises and metropolises according to this new categorization. China has also implemented a series of strategic policies to promote regional development in the middle and western parts of the country, where Wuhan (7.54 million in 2010), Chengdu (6.32 million in 2010), and Chongqing (6.26 million in 2010) are three representative centers driving regional development. In general, the population growth in 1990–2000 is greater than that in 2000–2010. With the rapid population growth in large cities, the eco-environment has been seriously threatened with intensive anthropogenic activities. As a result, cities such as Beijing have issued various population control policies and adjusted their urban planning to promote sustainable city development.
The investigation of city developments in Brazil, India, and China has shown that cities have been categorized into different levels. The coastal areas in Brazil and China have exhibited strengths with respect to city development, whereas Indian cities are spatially balanced. Increased urbanization level and growth rate have accelerated the expansion of cities demographically and spatially. Nevertheless, city development has brought great challenges to these urban agglomerations because the carrying capacity of natural resources is limited. As a result, sustainable urban development is expected to be in a balanced state between concentration and deconcentration, thereby requiring the adjustment of city size.
7. Comparison of Sustainable Development in BIC
In this section, the sustainability status quo is discussed in the context of rapid urbanization and is decomposed into four parts, namely, rural–urban relation, industry, city development, and landscape pattern in Brazil, India, and China. These countries were selected as research subjects not only because of their identification as “BIC” countries worldwide but also in view of their representativeness as fast-growing, developing countries that encounter various sustainability problems. The distinguishing features were identified for comparisons and policy implications by exploring the trajectories of urbanization and related sustainable issues in these countries (
Table 8).
The relationships between urban and rural residents as well as their living conditions determine social sustainability. The urban population of BIC continues to grow, but the changes in their rural population vary from one another. We determined that the rural–urban dichotomy exists in these countries, with India and China having a higher degree than Brazil. In Brazil and India, poverty problems appear in urban and rural areas, and favelas and slums emerge on a large scale. In China, many remote villages are highly impoverished and backward. Even in urban areas, the Chinese characteristic “urban villages” appear to accommodate rural migrants and low-income residents. The number of urban residents in developing countries is predicted to increase, thereby requiring the reduction of the urban–rural gap and the acquisition of the solution to the extreme poverty problem. “Encouraging” policies such as the reform in housing and employment system need to be implemented for rural migrants or rural residents. The coordination of urban and rural development is an indispensable means to relieve the increasing socio-economic pressure and ecological conflicts in urban agglomerations and to improve human well-being in an all-around manner.
The economic outputs in the agricultural, manufacturing, and service sectors demonstrate the sustainability of industrial structure and economic development. The sectors that dominate Brazil, India, and China vary. The service sector is dominant in Brazil, justifying its superior position in economic development among the three countries. The industrial transformation of India is remarkable, and its dominant sector has gradually changed from agriculture to the service sector. Accordingly, a considerable proportion of the agricultural outputs, the number of high-tech products, and its related business have grown tremendously in the country. In the past half-decade, China has been considered an industrial country because its manufacturing sector continues to be the primary economic contributor. However, China’s manufacturing industry is a highly resource-consumed sector and threatens its environmental sustainability to a great extent, whereas its agriculture development is closely associated with food security. In this sense, the industrial transformation in India should be affirmed, and China devotes great efforts to strengthen its service sector and optimize its industrial structure. The relationship between economic development and urbanization growth rate is a useful indicator of a harmonious development. Brazil has a typical economic-lead pattern, but its different sectors show different relationships with urbanization in terms of their growth rate in India and China.
Cities are the aggregation of resources, wealth, and knowledge, and city development is the embodiment of urban sustainability. In the past half-decade, the number of large cities remains stable in Brazil and shows great increases in India and China. The distribution of these large cities follows a regional pattern, with Brazil being northeast-focused, China being southeast-focused, and India being comparatively balanced. The population size of these large cities has continuously increased in the past several decades. In China, the growth is more rapid in the 1990s when counties and towns developed massively than in other periods. In the face of approaching growth limits in mega-cities in countries such as China, urban planning is oriented to be regionally balanced. Medium-sized cities and towns with predictable potential are also encouraged to be supported for development. Sustainability in cities at different levels is an issue of strategic layout in guaranteeing spatial superiority and spatial equilibrium.
Landscape pattern is an important issue in Brazil, India, and China not only because of their large geographical areas but also on account of their distinctive land use pattern. In general, abundance in resources is conducive to natural resilience and improved ecosystem service. Approximately 60% of Brazil is occupied by the Amazon forest, making this country a special place as “the kingdom of plants and animals.” This distinction also brings great challenges to Brazil with respect to the conservation of biodiversity and eco-environment. Physical difference determines the appearance of the northwest–southeast dividing line in land use distribution, in which human activities concentrate in the southeastern area. In the 1950s and 1960s, Brazil approved the opening of Amazon regions, where new towns and cities began to thrive. In the past half-decade, the conflicts between rapid urbanization and the protection of natural environmental have increasingly become severe, and they have aroused widespread attention on conservation measures. India is a cropland-dominated country whose land distribution is relatively random, whereas the land use in China is primarily mixed with cropland, forest, and grassland. Both of these countries have encountered tremendous urban expansion or sprawl in the past several decades, and the loss of arable land has made food security a critical issue for the growing population. Similar to the land use in Brazil, the land use distribution in India and China also shows a northwest–southeast dividing line because the development is apparently lagging behind the northwestern area. In the future, based on the characteristic physical conditions, adjusting measures are expected to be undertaken to improve resource efficiency and achieve an improved ecological environment. Landscape pattern is a socio-ecological term that measures the spatial aggregation or dispersion in urban areas and reflects the spatial vulnerability and resilience in urban ecosystem. In most cases, the fundamental data sources are considered land use maps in raster format. We chose more than 80 representative cities to explore urban landscape patterns using landscape indices such as CONTAG and SHDI. Among the BIC, China shows the most obvious land use fragmentation, and India has the least. India and China have extremely high population densities, which necessitate intensive land use. Compared with India, China has experienced a significantly faster urbanization with extensive use of urban and rural settlement. In recent years, a series of policies have been implemented to promote the intensive use of resources and energy in cities, towns, counties, and villages. Brazil shows the highest degree of land use diversity, whereas India has the least value. This phenomenon is partly attributed to the difference in biodiversity and ecological resilience among such countries. A healthy urban ecosystem requires the diversity in land use to guarantee ecological balance, especially in “vulnerable” urban environments. In this sense, India and China should take specific measures to protect their urban ecosystem such as delineating the conservation zones to realize urban sustainability.
The urbanized world has brought challenges and opportunities for a sustainable urban environment. This study explores the interaction between urbanization and sustainability from four aspects, namely, rural–urban relation, industrial coordination, city development, and urban landscape pattern. As part of the “BRIC” countries, Brazil, India, and China are used as the study areas to reveal their distinctive trajectories. In general, these countries show obvious rural–urban gaps with characteristic poverty problems threatening social sustainability. The industrial structures of these countries are inclined to be dominated by the service sector, whereas the agricultural sector is important for food security, and the manufacturing sector is still a formidable component in China’s economy. Similar to India, Brazil and China also demonstrate spatial clustering in the distribution of city development, and the most recent decade has seen the decline of the growth rate of these agglomerations largely attributed to the limits of natural carrying capacity. With respect to landscape pattern, China is more dispersed in urban land use than the other two countries, thereby requiring an increasingly pragmatic and intensive land use program. The landscape diversity in Brazil is the highest, increasing the country’s resilience in urban ecosystem. All these qualitative and quantitative analyses are undertaken to compare representative developing countries and provide reference for sustainable urban development in the context of rapid urbanization in the future.