A Meta-Analysis of Global Urban Land Expansion

Abstract

The conversion of Earth's land surface to urban uses is one of the most irreversible human impacts on the global biosphere. It drives the loss of farmland, affects local climate, fragments habitats, and threatens biodiversity. Here we present a meta-analysis of 326 studies that have used remotely sensed images to map urban land conversion. We report a worldwide observed increase in urban land area of 58,000 km2 from 1970 to 2000. India, China, and Africa have experienced the highest rates of urban land expansion, and the largest change in total urban extent has occurred in North America. Across all regions and for all three decades, urban land expansion rates are higher than or equal to urban population growth rates, suggesting that urban growth is becoming more expansive than compact. Annual growth in GDP per capita drives approximately half of the observed urban land expansion in China but only moderately affects urban expansion in India and Africa, where urban land expansion is driven more by urban population growth. In high income countries, rates of urban land expansion are slower and increasingly related to GDP growth. However, in North America, population growth contributes more to urban expansion than it does in Europe. Much of the observed variation in urban expansion was not captured by either population, GDP, or other variables in the model. This suggests that contemporary urban expansion is related to a variety of factors difficult to observe comprehensively at the global level, including international capital flows, the informal economy, land use policy, and generalized transport costs. Using the results from the global model, we develop forecasts for new urban land cover using SRES Scenarios. Our results show that by 2030, global urban land cover will increase between 430,000 km2 and 12,568,000 km2, with an estimate of 1,527,000 km2 more likely.

Detecting change in urban areas at continental scales with MODIS data

“…The consequences of urbanization are largely contingent on the size, location, and configuration of development (Weng, 2001;Zhou et al, 2004), with many environmental impacts exacerbated when new growth is expansive and/or fragmented in form (Alberti, 2005). A meta-analysis of urban expansion indicates that localto regional-scale studies are geographically biased, leaving even many large cities unstudied (Seto et al, 2011). Detailed maps on regional-to global-scale changes in urban land do not exist; previous efforts have been sample-based (Angel et al, 2005;Schneider & Woodcock, 2008), focused on one country (Homer et al, 2004;Wang et al, 2012), or drawn conclusions from datasets with substantial temporal and spatial mismatch and variability in how cities are defined (Seto et al, 2010).…”

Building a Better Urban Picture: Combining Day and Night Remote Sensing Imagery

“…However, its utilization has been greatly impeded due to cloud and cloud shadow contamination and inadequate algorithms to analyze them. Consequently, the vast majority of the applications are confined to individual small regions [13]. In terms of cloud cover, a Landsat scene (185 km by 185 km) could be in one of the three statuses: clear (no clouds in the scene), partially contaminated (with some clouds but part of the land can still be seen from space), or completely contaminated (with 100% cloud cover).…”

“…In fact, it has been the main resource in mapping urban areas, especially since its availability to the public as of 2008 at no charge [12]. In a meta-analysis of global urban land expansion, Seto et al [13] reported a total of 326 studies that have used remotely sensed images, mainly from Landsat, to map urban land conversion scattered around the world up to the year 2000. Although Landsat has contributed significantly to the understanding of urban land cover and land use change, these efforts have largely focused on individual city or city-region studies, with few comparative or global-scale studies at the Landsat resolution [13].…”

“…In a meta-analysis of global urban land expansion, Seto et al [13] reported a total of 326 studies that have used remotely sensed images, mainly from Landsat, to map urban land conversion scattered around the world up to the year 2000. Although Landsat has contributed significantly to the understanding of urban land cover and land use change, these efforts have largely focused on individual city or city-region studies, with few comparative or global-scale studies at the Landsat resolution [13]. This is mainly due to the Landsat data availability at the time, the limitation of computing facility, and algorithms to analyze the data.…”

Graph-Based Urban Land Use Mapping From High Resolution Satellite Images

“…The consequences range from land cover change to climate impacts, habitat loss, or extinction of species. Additionally it influences transportation developments, energy demand, or the automobile market (Seto et al, 2011). The main drivers in Europe, mentioned by the European Environment Agency, are e.g.…”