The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones

TLDR

Coastal lowlands, covering only 2 % of land yet hosting 10 % of the global population, are highly vulnerable to climate‑change risks and are experiencing rapid settlement growth, especially in countries like China where urbanization is shifting populations toward the coast. The study aims to conduct the first global review of population and urban settlement patterns in the Low Elevation Coastal Zone (LECZ) to inform strategies for reducing climate‑change disaster risks. The authors analyze the LECZ—defined as the contiguous coastal area below 10 m elevation—by compiling and mapping global population and urban settlement data. The LECZ contains 10 % of the world’s population and 13 % of its urban population, with disproportionate representation in small island states and large delta regions; Least Developed Countries have a higher share of residents (14 %) than OECD countries (10 %), and nearly two‑thirds of megacities (pop > 5 M) are at least partly located within the zone.

Abstract

Settlements in coastal lowlands are especially vulnerable to risks resulting from climate change, yet these lowlands are densely settled and growing rapidly. In this paper, we undertake the first global review of the population and urban settlement patterns in the Low Elevation Coastal Zone (LECZ), defined here as the contiguous area along the coast that is less than 10 metres above sea level. Overall, this zone covers 2 per cent of the world's land area but contains 10 per cent of the world's population and 13 per cent of the world's urban population. A disproportionate number of the countries with a large share of their population in this zone are small island countries, but most of the countries with large populations in the zone are large countries with heavily populated delta regions. On average, the Least Developed Countries have a higher share of their population living in the zone (14 per cent) than do OECD countries (10 per cent), with even greater disparities in the urban shares (21 per cent compared to 11 per cent). Almost two-thirds of urban settlements with populations greater than 5 million fall, at least partly, in the zone. In some countries (most notably China), urbanization is driving a movement in population towards the coast. Reducing the risk of disasters related to climate change in coastal settlements will require a combination of mitigation, migration and settlement modification.