Spatial gradients of urban land density and nighttime light intensity in 30 global megacities

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

The spatial agglomeration of urban elements results in the center-periphery urban structure, but the difference in spatial gradients of socioeconomic and physical elements is unclear. This study investigates how urban land density (ULD) and nighttime light intensity (NLI) decline with the distance to center(s) using the inverse-S function. Taking 30 global megacities as examples, we acquired their urban land and nighttime light in 2020 to represent urban physical and socioeconomic elements, respectively. ULD and NLI in concentric rings have been calculated to compare their spatial gradients from the city center(s). Results show that both ULD and NLI decrease slowly around city centers, followed by a relatively quick decline to suburban areas, and then decrease slowly again to a background level, showing an inverse-S shape. This spatial gradient can be well-fitted by the inverse-S function, whose parameters reflect disparities in urban extents and urban forms. NLI decreases faster than ULD, resulting in smaller radii (extents) of NLI, which shows the spatial agglomeration of socioeconomic elements is more obvious than that of physical space. This gap requires balanced development of socioeconomic and physical elements in megacities to avoid low-density urban sprawl and promote sustainable urban development.

Related collections

Most cited references 52

Record: found
Abstract: found
Article: found

Is Open Access

A Meta-Analysis of Global Urban Land Expansion

Karen Seto, Michail Fragkias, Burak Güneralp … (2011)

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.