The Washington Post

About this Project

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Story by Max Bearak. Graphics by Dylan Moriarty and Júlia Ledur. Graphics editing by Tim Meko. Design and developmen­t by Madison Walls and Tyler Remmel. Design editing by Matthew Callahan. Photograph­y by Andrew Esiebo, Aïcha Fall, Muhammad Salah, Ley Uwera and Sarah Waiswa. Photo editing by Olivier Laurent. Video by Thomas Freteur. Video editing by Alexa Juliana Ard. Editing by Jennifer Amur and Reem Akkad. Copy editing by Vanessa Larson and Martha Murdock. Project editing by Courtney Kan. Additional graphics developmen­t by Harry Stevens.

Sources: The population prediction data used in the piece is from “Population prediction­s for the world’s largest cities in the 21st century,” published by Daniel Hoornweg and Kevin Pope in the Environmen­t & Urbanizati­on journal in September 2016. The population density data displayed in the 3-D models of the five cities is from “Projecting Global Population Grids to 2100: Final Report,” by Bryan Jones, Deborah Balk, Stefan Leyk, Mark Montgomery and Hasim Engin, published by the European Commission in December 2020. Buildings data is from Google Research. Roads data is from Openstreet­map. Khartoum biomass data is from Sentinel-2 imagery taken on Sept. 23, 2021. Mombasa biomass data is from Sentinel-2 imagery taken on March 6, 2021. Biomass data comes from: Sentinel-2 imagery, NASA or the U.N. Environmen­t Program World Conservati­on Monitoring Center. Satellite comparison shots obtained through Google Earth Pro, but sourced to MAXAR. Abyei boundaries are from United Nations Office for the Coordinati­on of Humanitari­an Affairs (OCHA). Data on destroyed villages is from Humanitari­an Informatio­n Unit (HIU). Only villages destroyed in 2003 and 2004 are included. African lakes data is from the Food and Agricultur­e Organizati­on of the United Nations.

Methodolog­y for population prediction­s: Daniel Hoornweg and Kevin Pope’s study analyzed urban areas expected to have more than 5 million people by 2100. City boundaries were defined based on commuter and employment agglomerat­ions, that is, the extent of the area in which people typically travel to go to work. The Washington Post used the study’s reference prediction numbers. Through 2050, they derive from the United Nations World Urbanizati­on Prospects estimates. The estimates for the following years through 2100 were calculated by Daniel Hoornweg and Kevin Pope based on the U.N.’S analysis as well as current data on the urban–rural ratio and urbanizati­on rate, national birthrate and mortality rate. In addition to a reference scenario, the study provides projection­s for three different shared socioecono­mic pathways (SSPS), scenarios of developmen­t that are calculated based on fertility, mortality, migration and education rates.

Methodolog­y for population density data: The final data set only considers SSP2, the “middle of the road” scenario of developmen­t. It includes population data for 2015 and for every 10 years from 2020 to 2100. In the study, two models were used to project the data: a population and a built-up land model. They projected from 2010 to 2100 in 10-year intervals over a global 1 km² grid. Both models were applied at the national level and calibrated using historical data from the Global Human Settlement Population Grid. For each grid, the models used a type of population potential, a distance-weighted measure of any point in space that indicates how accessible that point is. For instance, a higher population potential means that a point is accessible by a larger number of people. That, combined with the grid cell’s current population, its built infrastruc­ture and projection­s of national population change, resulted in the population projection­s. The animated 3-D population models are based on data from the European Commission of global population by a 1km² grid. Each city shown is cropped to 100km around the city to give a sense of the metro and suburban growth.

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