Dramatic uneven urbanization of large cities throughout the world in recent decades

TLDR

The world has experienced dramatic urbanization in recent decades. We lack information on the characteristics of urbanization in large cities worldwide. We analyzed 841 large cities with built‑up areas over 100 km² from 2001 to 2018 and found uneven urbanization across economic levels. Low‑income and lower‑middle‑income cities showed the highest urban population growth, upper‑middle‑income cities expanded built‑up areas more than three times that of high‑income cities, and over 10 % of built‑up areas in 325 cities greening significantly—China alone contributed 32 % of greening, benefiting 108 million residents—highlighting the need for sustainable urbanization in developing countries.

Abstract

Abstract The world has experienced dramatic urbanization in recent decades. However, we still lack information about the characteristics of urbanization in large cities throughout the world. After analyzing 841 large cities with built-up areas (BUAs) of over 100 km 2 from 2001 to 2018, here we found an uneven distribution of urbanization at different economic levels. On average, large cities in the low-income and lower-middle-income countries had the highest urban population growth, and BUA expansion in the upper-middle-income countries was more than three times that of the high-income countries. Globally, more than 10% of BUAs in 325 large cities showed significant greening ( P < 0.05) from 2001 to 2018. In particular, China accounted for 32% of greening BUAs in the 841 large cities, where about 108 million people lived. Our quantitative results provide information for future urban sustainable development, especially for rational urbanization of the developing world.