A global analysis of human settlement in coastal zones

TLDR

Recent mapping advances allow more accurate estimation of coastal populations, highlighting the need for higher‑resolution data to improve baseline and policy scenarios. The study aims to integrate updated population estimates, settlement imagery, elevation data, and coastline geometry to generate bivariate distributions of population, settlements, and land area. By overlaying population, settlement, and elevation data, the authors compute bivariate distributions of population, lighted settlements, and land area relative to elevation and distance from shore. The analysis estimates 1.2 billion people within 100 km of shore and 100 m elevation, with densities about three times the global average; densities fall more steeply with elevation than distance, lighted settlements cluster within 5 km of coast, and most near‑coastal residents live in rural or small‑to‑medium cities rather than large urban centers.

Abstract

Recent improvements in mapping of global population distribution makes it possible to estimate the number and distribution of people near coasts with greater accuracy than previously possible, and hence consider the potential exposure of these populations to coastal hazards. In this paper, we combine the updated Gridded Population of the World (GPW2) population distribution estimate for 1990 and lighted settlement imagery with a global digital elevation model (DEM) and a high resolution vector coastline. This produces bivariate distributions of population, lighted settlements and land area as functions of elevation and coastal proximity. The near-coastal population within 100 km of a shoreline and 100 m of sea level was estimated as 1.2 X 10(9) people with average densities nearly 3 times higher than the global average density. Within the near coastal-zone, the average population density diminishes more rapidly with elevation than with distance, while the opposite is true of lighted settlements. Lighted settlements are concentrated within 5 km of coastlines worldwide, whereas average population densities are higher at elevations below 20 m throughout the 100 km width of the near-coastal zone. Presently most of the near-coastal population live in relatively densely-populated rural areas and small to medium cities, rather than in large cities. A range of improvements are required to define a better baseline and scenarios for policy analysis. Improving the resolution of the underlying population data is a priority.