Abstract
Abstract. The accurate estimation of population living in the low-elevation coastal zone (LECZ) – and at heightened risk from sea level rise – is critically important for policymakers and risk managers worldwide. This characterization of potential exposure depends on robust representations not only of coastal elevation and spatial population data but also of settlements along the urban–rural continuum. The empirical basis for LECZ estimation has improved considerably in the 13 years since it was first estimated that 10 % of the world's population – and an even greater share of the urban population – lived in the LECZ (McGranahan et al., 2007a). Those estimates were constrained in several ways, not only most notably by a single 10 m LECZ but also by a dichotomous urban–rural proxy and population from a single source. This paper updates those initial estimates with newer, improved inputs and provides a range of estimates, along with sensitivity analyses that reveal the importance of understanding the strengths and weaknesses of the underlying data. We estimate that between 750 million and nearly 1.1 billion persons globally, in 2015, live in the ≤ 10 m LECZ, with the variation depending on the elevation and population data sources used. The variations are considerably greater at more disaggregated levels, when finer elevation bands (e.g., the ≤ 5 m LECZ) or differing delineations between urban, quasi-urban and rural populations are considered. Despite these variations, there is general agreement that the LECZ is disproportionately home to urban dwellers and that the urban population in the LECZ has grown more than urban areas outside the LECZ since 1990. We describe the main results across these new elevation, population and urban-proxy data sources in order to guide future research and improvements to characterizing risk in low-elevation coastal zones (https://doi.org/10.7927/d1x1-d702, CIESIN and CIDR, 2021).
Highlights
Climate change threatens people around the world but in locations where concentrations of people can be expected to overlap with concentrations of physical hazards resulting from climate change
Using our core data sets as described above (MERIT digital elevation models (DEMs), GHS-POP and GHS-SMOD), we find that for 2015, 815 million persons globally live in the ≤ 10 m Low-elevation coastal zones (LECZs), with nearly 300 million of those persons living in the higher-risk ≤ 5 m zone
About 60 % of the population of the LECZ live in locations classified as urban, and another 24 % live in quasiurban areas
Summary
Climate change threatens people around the world but in locations where concentrations of people can be expected to overlap with concentrations of physical hazards resulting from climate change. Low-elevation coastal zones (LECZs) are likely to contain a disproportionate and growing share of such locations. Sea level rise and a greater prevalence of extreme weather events are correlates of climate change and heighten the risks of flooding, coastal erosion, groundwater salinization and other hazards in low-lying coastal areas (Oppenheimer et al, 2019). Urbanization and related water abstraction, especially in deltas where natural subsidence is often already occurring, can contribute to subsidence, which adds to and amplifies the hazards associated with sea level rise and extreme weather events. The principal purpose of delineating a low-elevation coastal zone (LECZ) is to identify the broad areas in which there are likely to be sub-populations at a heightened and rising risk of exposure to selected hazards being exacerbated by climate change. The hazards of particular concern here are those arising from sea level rise and more extreme weather events and being aggravated by land subsidence where that is occurring
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