Population pattern and exposure under sea level rise: Low elevation coastal zone in the Yangtze River Delta, 1990–2100

Abstract

Abstract The low elevation coastal zone (LECZ) in the Yangtze River Delta (YRD) is a critical and highly sensitive area to climate change and sea level rise (SLR). Population is a key element in disaster risk management and climate change adaptation. Employing a variety of datasets including gridded population data, DEM data, sea-level extremes data, and urban boundary data, this study explores the spatiotemporal patterns and dynamics of population in the LECZ of YRD, and estimates the population exposure to inundation in the context of SLR over 1990–2100. Our results show that: (1) the population in the LECZ in 2015 approximates 104 million, with an increase of 29.3 million (39.2%) over 1990. There shows a trend of remarkable population growth in areas close to the coastline (less than 40\xa0km from the coastline) and in areas at lower altitudes (below 4\xa0m above sea level). Meanwhile, driven by rapid urbanization, population in the LECZ concentrates steadily in urban areas with increasing spatial polarization and heterogeneity. (2) In 2020–2100, the projected population in the LECZ of YRD will experience a rise followed by a fall. Under shared socioeconomic pathways (SSPs) with various factors of fertility, mortality, migration and urbanization levels, population will rise gradually from 2020 to 2040 with a peak of near 132 million (SSP5), and then fall remarkably until 2100. (3) Overlaying the SLR with representative concentration pathways (RCPs), the exposed population to inundation will reach 86 million (RCP4.5-SSP2) and 100 million (RCP8.5-SSP5) by 2050, an increase of 13.5% and 32.2% over 2015, respectively. The exposed population will then decrease to 55 million (RCP4.5-SSP2) and 63 million (RCP8.5-SSP5) by 2100, slightly lower than those in 2015. In contrast to population growth, the contribution of SLR to population exposure will steadily increase. (4) Long-term trend of population exposure to SLR will pose considerable challenges to the regional development and planning. Different adaptation efforts should be taken in urban and rural settlements to avoid exacerbating impacts induced by SLR.