The climate‐water‐health nexus in emerging megacities

Today a handful of developing nations (India, China, Nigeria, Brazil, Bangladesh, Indonesia, and Pakistan) account for more than half of the world's population. A majority of these nations are rapidly urbanizing, as people from remote regions migrate in search of economic prosperity [ Cohen , 2003]. Such a rural‐to‐urban migratory trend has been the leading cause of cities expanding to megacities, which are defined by the United Nations as cities with a population greater than 10 million. By 2025 a greater proportion of the world's megacities, most of them situated in low‐lying coastal areas, will be in developing nations in Asia and Africa (Figure 1a) [ Asian Development Bank , 2012].