Urban land expansion
The number of urban dwellers worldwide is expected to increase by 2.5 billion over the next 30 years. However, there is limited understanding of how this growth will affect urban sprawl (ULE). Here, we develop a comprehensive study to explicitly assess the relative importance of urban population and Gross Domestic Product (GDP) in affecting ULE in the various regions, economic development levels, and forms of governance of 300+ cities.
Our results show that population growth, in excess of GDP, remains a major factor in ULE between 1970–2014. However, the effect of GDP growth on ULE grows significantly after 2000. In countries with strong governance, economic growth has a greater impact on ULE than population growth. We find that urban population growth and ULE are related but these relationships vary from country to country in different developmental stages. Finally, this study shows that good governance is a necessary condition for economic growth to affect ULE.
Urbanization is a process that combines both urban population growth and urban land transformation1. However, there is very little understanding of the relationship between urban population growth and urban land expansion. What explains the physical growth of cities? Does overcrowding in urban areas lead to an increase in urban land? Or do economic activities encourage a change in urban land use? With predictions of urban population growth of 2.5 billion worldwide between 2018 and 2050, there is an urgent need to understand how these massive fluctuations in statistics could affect urban sprawl.
The urban change affects biogeochemical cycles, regional climate to global, hydrological systems, and biodiversity2. The growth of urban areas is closely linked to the emissions of urban pollutants per capita. The fragmentation of habitats and the loss of biodiversity4,5, the misuse of natural resources5, and the loss of agricultural land6,7. Strong urban growth goes hand in hand with improved outcomes for human health8, economic growth9, energy and resource efficiency10.
ULE decision studies are usually focusing on one city11,12, cities in one country13,14, or cities within a district15,16. Only three studies1,17,18 surveyed the drivers of urban sprawl around the world. Each of these studies focuses on a specific year or period of fixed GDP data. All of these studies (domestic or international) examine the potential features of ULE (e.g., slope, arable land, temperature, population, etc.). And show that ULE is driven by many factors. With mathematical or economic growth as a primary19,20, 21.
These findings support the theory from urban economics and urban science
That cites population and income as the main causes of ULE. For example, the urban economy identifies land demand as a demand based on external factors such as population and income. Recent theological advances — urban science — point to measurement laws relating to urban populations, wealth, and location22. Detailed examples of studies also highlight the effects of local policies and laws such as local and housing policies23, territorial standard24, transport infrastructure funding, and foreign direct investment25 as additional drivers for ULE.
Although local or regional studies provide insight into the causes of urban sprawl in a particular area, it is difficult to generalize the results of other areas. In addition, most of these studies in ULE focused on cities in Europe, North America, and China26,27.
Here lies the scale and spatial differences between scientific knowledge about urbanization and modern urbanization conditions around the world: urban population growth over the next three decades will be in developing countries with low levels of economic development but yet limited understanding of ULE processes in these areas. The United Nations (UN) estimates that up to 70 percent of urban population growth will occur in only 20 countries (Appendix 1, UN, DESA28), all but one in developing or less developed countries.
This is important because there is a strong correlation between the rate of urbanization and the level of national average income. In 2018, high-income countries had an average urbanization rate of 81%, while low-income countries had an average urbanization rate of 32% (UN, DESA28). Although the relationship between cities and the national currency is complex, there is strong evidence that as countries become cities, national incomes also rise.
However, there are significant differences in national incomes in countries with similar urbanization rates
Some of these differences may be due to differences in governance and institutions. There is ample evidence that effective institutions and governance are the conditions for cities to deliver municipal services and create healthy, equitable, and resilient communities 29.30. Legislation and effective governance are needed to create an attractive environment for private investment. Required for infrastructure, industry, and innovation31,32. Cities that are well-governed, those with safe roads, clean water. And health services often have functioning facilities.
Collectively, the literature points to urban population growth, economic development, governance, and institutions as key drivers of urban growth. However, because most of the available literature tends to focus on one case study. As well as the various dynamic tests that may be testing driving ULE. There is very little understanding of how the level of economic development. And the statistical change affects ULE in all different contexts, especially provinces, countries, or cities.
This study fills these information gaps. Our research differs from previous studies in that it focuses exclusively on people and economic growth as outstanding drivers of ULE. And examines how local region, economic development, and quality of national governance affect the related significance of these factors.
To date, we are actively examining the relative importance of population growth. And GDP growth in setting up ULE in all 300 cities. And over 45 years in two separate periods (1970–2000 and 2000–2014). We also consider the role of governance. Which has not been considered in any previous study. As a factor in determining the effects of economic growth and population growth on ULE.
The key question we ask is
What is most important about ULE under different local conditions, development, and institutions: population or GDP growth? Does our analysis answer the following questions:
(1) What are the metropolitan patterns of population growth, economic growth, and ULE in global regions during 2000–2014?
(2) What makes ULE more: population or economic growth?
(3) How does the relative importance of urban population growth and economic growth change in all local regions, national revenue levels, and institutional arrangements?
This analysis is based on the concept of town measurement and city expansion accounting framework (introduced Appendix Note 1). City estimates refer to the assumption that large urban structures. Such as greenhouse gas emissions and the level of urban space, reflect the growing relationship with the urban population33,34,35. We are building a growth statistics model for urban land expansion, based on the city’s metrics. A growth account is a tool for developing economists36. To divide the growth of interest rates into several categories. Our model divides urban growth into two major aspects of the theoretical framework: urban population growth and urban productivity growth.