Opportunities & risks associated with global glacial meltwater changes and regional population growth from 1980 to 2100

Mountain glacier is an indispensable supplier and modulator of freshwater to human’s sustenance in extensive cold and arid areas of the world. Melt waters from glaciers are widely used for ecosystem integrity, agricultural irrigation, hydropower operation, domestic and industrial activities. Under the background of global environmental changes such as global warming and regional population growth, linking climate-related glacio-hydrological changes to regional population growth is of the essence. However, a global assessment on opportunities/risks caused by glacial meltwater changes and population growth has not been presented until now. In this study, the population changes in glacier-fed area (GFA) for historical (1980-2015) and future (2010-2100) periods at the global, continental, national and basin scales were first mapped. Then, the opportunities/risks associated with population growth and glacier meltwater changes during 1980-2100 in 42 large-scale glacierized drainage basins with a minimum population of 10 thousand in 2015 were analyzed. Results reveal that the population living in the world’s GFA was 2030 million in 2015 and it was rapidly increased from 1278 million in 1980. The total population in GFA would continue to increase until a maximum is reached (e.g. peak population will appear around 2060 under the intermediate pathway for mitigation and adaptation, i.e. SSP₂), beyond which the population would gradually decline. The opportunities/risks vary across basins and decades. Both of them are greatest in the Indus River basin, where the increase in glacial meltwater can seasonally satisfy the basic needs of additional 87 million people from the 2000s to 2040s, but about 200 million would be exposed to severe water scarcity due to the decrease in glacial meltwater and the population increase after the 2040s.