Is rapid urbanization of low-elevation deltas undermining adaptation to climate change? A global review

Abstract

Climate change is putting low-lying coastal zones at increased risk, through higher sea levels and changes in the weather. Deltas are subsiding, compounding such risks. Confirming past research, we find roughly 10 per cent of the world’s population and an even higher share of its urban population are located in coastal areas under 10 metres in elevation (LECZ10), with Asia dominating these statistics. However, according to our estimates for 2015, the deltaic LECZ10 is 2.6 times as densely populated and 1.7 times as built-up as the non-deltaic LECZ10. The deltaic LECZ10 accounts for only 0.35 per cent of the world’s land, but over 10 times the population share (279 million people). Population and built-up area growth rates remain higher in the deltaic LECZ10, and especially its cities. Indeed, for 1990–2015 the urbanization rate of the deltaic LECZ10 is double that in the non-deltaic LECZ10. Given the path dependency of urbanization, this risks locking in maladaptive settlement patterns.