Global-scale analysis of coastline expansion in the era of rising sea levels

Abstract

Continued greenhouse gas emissions have caused global sea levels to rise, leading to coastal erosion and flooding. However, some regions worldwide are experiencing coastline expansion, while the drivers are often overlooked. In this study, we conducted an intensive analysis of significantly expanding (>1 km) coastlines worldwide based on the Global Long-term Shoreline Evolution (GLSE) dataset between 1986 and 2016. The study employs the interpretation of remote sensing imagery to identify and categorise coastline types comprehensively, focusing on the main drivers of coastline expansion. Coastline types include natural (e.g. rocky, sandy, muddy, and biological) and artificial (e.g. traffic, aquaculture, port, and embankment) coastlines. At the global scale, 2939 km of coastline experienced significant expansion, with aquaculture coastlines dominant at 22%, followed by biological (17%) and muddy coastlines (15%). At the national level, China accounted for 27% of global expansion, driven primarily by artificial factors (43% aquaculture), while Brazil exhibited the highest natural expansion (97% biological coastlines). At the continental scale, Asia’s coastline expansion was predominantly artificial (34%), whereas Africa and South America were dominated by natural drivers (88% and 94%, respectively). Among deltas, aquaculture constituted 36% of expansion, with the Yellow River Delta showing the highest mean expansion (3369.7 m) and the Nile Delta reaching a maximum of 9920.6 m. This study not only deepens our understanding of how sea-level rise and human activities affect coastlines but also offers valuable insights into the sustainable management and utilisation of coastal resources.