World agglomerations growth

Explosive growth in urban populations presents a wide range of societal, environmental, and economic consequences; in developing nations, in particular, many aspects of urban infrastructure are inadequate already for the needs of today’s population, and accommodating rapid future growth will require major improvements in urban planning, for which accurate population estimates are essential. As just one example, the 11th item in the United Nations’ Sustainable Development Goals pledges to “make cities and human settlements inclusive, safe, resilient and sustainable,” and the associated 2030 objectives have spurred cities to introduce a variety of initiatives—in areas such as housing, transportation, public health, and environmental protection—whose implementation depends crucially on urban-population projections.

Needless to say, urban-population growth is projected to continue well beyond 2030, while the consequences of climate change will affect the sustainability and resilience of cities on even longer timescales, and thus urban-population projections must extend not only into the near term, but ideally several decades into the future. Beyond their key role in urban planning, long-term projections of the spatial distribution of future populations have been used to assess risks associated with phenomena such as climate-change-induced flooding, heat waves, malaria epidemics, food security, biodiversity, and freshwater availability, and have also been researched for more general purposes; in contrast to the regional scope of urban-planning applications, the global scope of such research studies often demands future projections of worldwide urban populations, and this is the challenge we address in this study.

Map was made for 30DayMapChallenge 2021