About 24% of the world’s freshwater fish, dragonfly, damselfly, crab, crayfish and shrimp species, are at high risk of extinction, according to a study co-published by the IUCN.

This global freshwater fauna assessment is the result of over 20 years of work by more than 1,000 experts from around the world.

Crabs, crayfishes and shrimps are at the highest risk of extinction of the groups studied, with 30% threatened, followed by 26% of freshwater fishes and 16% of dragonflies and damselflies.

Catherine Sayer, IUCN’s Freshwater Biodiversity Lead and lead author on the paper, said “as the IUCN Red List celebrates its 60th anniversary, it is a stronger barometer of life than ever. Lack of data on freshwater biodiversity can no longer be used as an excuse for inaction.”

Sayers also said freshwater landscapes are home to 10% of all known species on Earth and key for billions of people’s safe drinking water, livelihoods, flood control and climate change mitigation, and must be protected for nature and people alike.

The report found that at least 4,294 species out of 23,496 freshwater animals on the IUCN Red List are at high risk of extinction.

The greatest number of threatened species are found in Lake Victoria, Lake Titicaca, Sri Lanka’s Wet Zone and the Western Ghats of India, according to the study.

These areas are home to some of the highest freshwater biodiversity in the world, including many species found nowhere else on Earth.

Pollution, mainly from agriculture and forestry, impacts over half of all threatened freshwater animals. Freshwater ecosystems are further degraded by land conversion for agricultural use, water extraction and the construction of dams, which also block fish migration routes. Overfishing and the introduction of invasive alien species have had a particularly strong role in driving extinctions. For example, the carp Squalius palaciosi, last seen in 1999, was declared Extinct this year due to habitat loss through the construction of dams and weirs and the introduction of invasive alien species in southern Spain.

The paper found that although the threatened freshwater animals studied tend to live in the same areas as threatened amphibians, birds, mammals and reptiles, they face different threats due to their specific habitats. Conservation action must therefore be targeted to these species.

Dr Rajeev Raghavan, South Asia Chair of the IUCN SSC Freshwater Fish Specialist Group and a co-author on the paper, said “although they live side by side in the Western Ghats, conservation action for tigers and elephants will not help the Critically Endangered humpbacked mahseer (Tor remadevii), which is threatened by habitat loss due to river engineering projects and sand and boulder mining, poaching and invasive alien species. Active protection of the river and tributaries where the humpbacked mahseer lives is essential to its survival, in addition to fishing regulations and banning the introduction of further invasive alien species.”

The study also revealed that areas with high water stress (where there is high demand and low supply) and areas with more eutrophication (where an excess of nutrients in the water leads to overgrowth of algae and plants) are not home to higher numbers of threatened species than areas with lower water stress and less eutrophication.

The IUCN World Conservation Congress in October is expected to guide conservation for the next four years, as the world works to achieve the Sustainable Development Goals and the Kunming-Montreal Global Biodiversity Framework targets by 2030. This information will enable policy makers and actors, to plan freshwater conservation measures where they are most needed.

Picture: IUCN

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