Disentangling the impact of global change on freshwater biodiversity decline

Freshwater ecosystems have higher proportions of extinct and threatened species than terrestrial and marine ecosystems, with populations of vertebrates declined by 83% between 1970 and 2018. The pressing question is: what are the main drivers for this decline? Here we investigate the reasons for the loss of freshwater biodiversity using globally available gridded datasets at 0.5° spatial resolution on precipitation and temperature, land cover and land use, water use and dams as well as daily hydrological streamflow simulations from the ISIMIP initiative.

Across the past 50 years, we constructed annual change maps of the environmental variables along the global river networks and calculated time-variant indicators of hydrologic alteration (IHA) to depict hydrological change. We then calculated normalized indicators (e.g. proportion of threatened species) describing the current freshwater biodiversity status through species data aggregation of the International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) categories.

By applying classification and regression trees (CART), we highlight the importance of environmental- and hydrological change on the freshwater biodiversity status based on IUCN Red List assessments on each grid cell globally. Our results reveal a large-scale spatial classification of the environmental variables and their potential impact on the ongoing freshwater biodiversity crisis.