A McGill-led global study mapped 45 human threats to more than 21,000 freshwater species, finding that farming, dams and runoff from agriculture are major pressures and that Europe and Northwest Africa are hotspots where conservation may be especially urgent.
The researchers used data from the International Union for Conservation of Nature to study 21,490 amphibians, fish, mammals, reptiles, dragonflies and damselflies. They produced 225 maps showing where specific threats may affect each group. By combining the maps, the team estimated how likely species in different watersheds are to face particular pressures.
The maps showed where species may face pressures, rather than simply where human activities occur. The results suggest that freshwater species face more intense threats than species living on land. They also suggest that the geographic pattern of these impacts differs from that for species living on land.
Pressures differ by region. Pollution from cities, agriculture and industry is prominent in Europe. Northwest Africa faces a combination of pollution, dams and heavy water use.
Agriculture particularly affects amphibians and dragonflies in many areas. Hunting is a concern for some freshwater mammals and reptiles. In parts of South America, agriculture and aquaculture also rank among the key risks.
The researchers say the maps provide a starting point to help conservationists target their responses. The findings matter for freshwater ecosystems, which support fisheries, drinking water and flood protection.