Farming and Dams Drive Freshwater Threats
An international study mapped 45 human-driven threats to 21,490 freshwater species across the globe.
Updated on Nov. 1, 2026 in Environmental
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Researchers mapped 45 human-driven threats affecting 21,490 freshwater species worldwide, finding that agriculture, dam construction and water use, and agricultural runoff have the greatest impact on freshwater ecosystems. The findings were published in the journal Science on October 29.
Why it matters
Freshwater areas cover 3.5% of Earth's surface yet host about one-third of all vertebrate species, making their decline a concern for global biodiversity. The results are expected to help identify regions where freshwater conservation is most urgently needed.
The team measured threat impact as the share of species in each sub-watershed affected by a given threat, then summed these probabilities across all 45 threats into a cumulative index. The highest index values were recorded in Europe and the Maghreb region, but the stub does not give the index values themselves.
The details
The international team analyzed freshwater species including amphibians, fish, mammals, dragonflies and damselflies, and reptiles at the sub-watershed level. Researchers concluded the highest-index areas have experienced extensive land development over a long period and show pronounced water pollution.
Timeline
October 29 (local time): Findings published in the journal Science.
Seasonal Patterns
The study applies the IUCN threat classification system to freshwater species at sub-watershed scale, extending a standardized framework to a habitat type that hosts about one-third of vertebrate species. It establishes a baseline for comparing where agriculture, dams and runoff concentrate pressure across regions.
Freshwater habitats support fish, amphibians, and other species that people depend on for food and water. Changes in agricultural practices, dam operations, and runoff control could alter the pressures these ecosystems face over time.
The takeaway
Protecting freshwater ecosystems depends on identifying where threats are most concentrated, and this mapping offers a starting point for prioritizing conservation effort.
Further reading
Explore more in our Environmental coverage.
Source note: This article includes information reported by Dongascience.
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