Global hotspots and trends in urban sprawl since 1990 and their relation to the Human Development Index (HDI): Europe has sprawled most dramatically
In just 40 years between 1975 and 2014, humans converted more land to settlements than in all previous millennia combined, since they had started building the very first villages and towns. This is a dramatic acceleration that is characteristic of the Anthropocene. Dispersed expansion of settlements at low densities is called “urban sprawl”. It has a number of detrimental environmental, economic, and social consequences such as higher greenhouse-gas emissions and loss of fertile soils and wildlife habitats. It poses a threat to the long-term availability of many vital ecosystem services and is in direct conflict with the urgent need for a sustainability transformation. We present the degree of urban sprawl on the planet at multiple spatial scales (continents, UN regions, countries, sub-national units, and a regular grid) for the period 1990–2014. Urban sprawl increased by 95 % in just 24 years, almost 4 % per year, with built-up areas growing by almost 28 km2per day, or 1.16 km2 per hour (1.9 ha per minute). Europe has been the most sprawled and also the most rapidly sprawling continent, by 51 % since 1990. At the scale of UN regions, the highest relative increases in urban sprawl were observed in East Asia, Western Africa, and Southeast Asia. Urban sprawl has increased significantly in fast-growing urbanized regions, particularly in coastal regions in China, West Africa, and India. In contrast, urban sprawl per capita has been highest in Oceania and North America, exhibiting a minor decline since 1990, while it has been increasing rapidly in Europe, by almost 47% since 1990. Urban sprawl is strongly linked to the level of human development as measured by the Human Development Index (HDI). Urban sprawl is an important issue of intergenerational justice because the built-up areas are passed on from one generation to the next. The results imply that it will be important for a more sustainable future to find a better balance between a high quality of life and using land more sparingly. There is an urgent need to stop urban sprawl, since current regulations and measures in developed countries are apparently not effective at limiting it. It is a remarkable irony in human development of recent decades that the more knowledge and planning capacity societies have at their disposal, the more common has been the emergence of high urban sprawl. Much greater efforts are needed to use land more sparingly, especially in developed countries. Monitoring urban sprawl can serve to guide policy development such as the implementation of targets and limits and to evaluate the effectiveness of urban growth management strategies at mitigating urban sprawl, such as greenbelts.