The United Nations has released its latest projections on global urbanisation, a periodically published outlook that plays a central role in providing insight into how cities around the world are expected to grow in the coming decades. A key part of the spatial forecasting in this edition of the ‘World Urbanization Prospects 2025’ was supported by researchers from Vrije Universiteit Amsterdam, who were acknowledged for their contribution.
At the heart of their input is the CRISP model, a new tool designed to translate national population projections into detailed, 1-kilometre global grids for the years 2020 to 2100. The publication, entitled ‘Introducing the CRISP model to downscale future population projections’ is authored by several current and former members of the Department of Spatial Economics and others, namely: Chris Jacobs-Crisioni, Marcello Schiavina, Katarzyna Krasnodębska, Lewis Dijkstra, Jip Claassens, Maarten Hilferink, Thijmen van der Wielen, and Eric Koomen.
Created to support the UN’s assessment of future urbanisation levels, CRISP offers a highly granular view of how populations and built-up areas may evolve. Its three-step approach includes:
- Estimating population and built-up area change for roughly 1,000 functional regions worldwide, grounded in national demographic forecasts.
- Allocating newly built-up land at the grid-cell level, considering factors such as proximity to existing settlements and roads, water bodies, and current urban density.
- Redistributing population within regions to account for internal migration patterns, growth in attractive areas, and decline in less suitable locations.
Beyond its role in the UN projections, the CRISP model opens the door to numerous other applications in global change research, urban planning, and policy analysis, providing a flexible framework for mapping long-term demographic and spatial trends.
The publication introducing the model formed an important methodological input for the UN’s ‘World Urbanization Prospects 2025’, one of the most widely referenced international studies on global urban growth.