4/28/2023 0 Comments Human population 0 ad![]() Understanding this relationship therefore informs global sustainable development efforts, including international cooperative frameworks like the UN Sustainable Development Goals (SDGs), and helps the calculation of indicators measuring progress toward various sustainability targets, for example, the SDG Indicator 11.3.1 (ratio of land consumption rate to population growth rate) (UN, 2015, 2017).ĭespite the apparent association, the relationship between population and built-up land varies across space, time, and scale, and can sometimes be counterintuitive (e.g., Geist et al., 2006 Seto et al., 2010). The spatiotemporal relationship between population and built-up land connects the social and the physical aspects of urbanization, and determines how urbanization interacts with many environmental changes (e.g., Balk & Montgomery, 2015 Hibbard et al., 2010 Sánchez-Rodríguez et al., 2005 Wolff et al., 2020). The two phenomena are related: new built-up land development may be demanded by various needs of the growing urban population (e.g., Bierwagen et al., 2010), and the form and functions of built-up land can affect the spatial distribution of population (e.g., Frolking et al., 2013). Rapid concentration of population and massive expansion of built-up land are two of its prominent features (AAAS, 2016). These changes in perspective suggest that urbanization's potential large-scale impacts may need to be re-evaluated.Ĭontemporary urbanization is profoundly transforming our world (e.g., Grimm et al., 2008 Wu, 2014). Moreover, most people in the world (including those considered urban people by national agencies, such as census) live in areas with less than 5% built-up land. Contrary to common impressions, we find developed and developing regions across the world experienced similar amounts of built-up land expansion during recent decades. We find the correlation between population and built-up land is about 60%, with the two showing some distinctly different spatial and temporal patterns. ![]() Using the newly-available data, we examine the relationship between population and built-up land across the world. Recently new global-coverage maps of population and built-up land became available. This assumption is influential for understanding people's vulnerability to natural disasters (for example, heatwaves, coastal storms) in urban areas, but has not been tested globally, largely due to the lack of data. These two expressions of urbanization (i.e., population concentration and built-up land expansion) have often been assumed to be strongly associated. Key PointsĬities and towns across the world have been expanding (a process known as urbanization) both in terms of population size and land areas. Especially, the common practice in large-scale earth system modeling of assuming demographically-defined urban population resides in areas with medium to high built-up land development levels should change. These changes in perspective suggest that urbanization's potential large-scale impacts may need to be re-evaluated, and lead to best-practice recommendations for urbanization modeling and analysis. Also, most global population, including what national statistics agencies call urban population, reside in areas with low land development levels (which are frequently less than 5% built up). While meta-analyses have reported that built-up land in urban areas expands globally on average twice as fast as population grows, our results show the global change rates of built-up land and population are similar. ![]() Contrary to common impressions, our results show that during recent decades, developed and developing regions across the world experienced comparable amounts of built-up land expansion. We find that population and built-up land show distinctly different spatial and temporal patterns (with a global correlation coefficient around 0.6). Using newly-available data, here we conduct the first global-coverage, spatial analysis of the relationship between (changes in) population and built-up land at multiple spatial scales, and compare to existing common beliefs about urbanization based on individual city studies. ![]() Existing literature on the population aspect of urbanization has mostly focused on national and regional aggregates, and literature on the land development aspect has often relied on spatial case studies of individual cities or their meta-analyses. Population concentration and built-up land expansion are two prominent features of contemporary urbanization.
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