By 2025, half of the world's population will live in urban areas, with 90% of that in developing nations. There will be 100 mega-cities with over 10 million people each, and India will see its urban population grow twice as fast as its total population, with major growth in its 35+ million-person cities. Urbanization has led to deforestation and environmental risks, but cities themselves are also at risk from issues caused by large populations and infrastructure stresses.