One Quarter of Freshwater Animals at Risk of Extinction

The largest global assessment of freshwater animals on the IUCN Red List of Threatened Species™ to date has revealed that 24% of the world’s freshwater fish, dragonfly, damselfly, crab, crayfish and shrimp species are at high risk of extinction, according to an analysis published in Nature. The IUCN co-authored study recommends targeted action to prevent further extinctions and calls for governments and industry to use this data in water management and policy measures. 

The study 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. 

Underground water systems around the world have been found to contain more threatened species than expected. For example, North America is home to a high number of threatened crayfish, such as the daisy burrowing crayfish (Fallicambarus jeanae) in Arkansas, which is Vulnerable on the IUCN Red List. Lakes, oases, and springs are hotspots for extinction. In 2020, fifteen fish species from Lake Lanao in the Philippines were declared Extinct on the IUCN Red List. 

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. 

“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,” said Dr Rajeev Raghavan, South Asia Chair of the IUCN SSC Freshwater Fish Specialist Group and a co-author on the paper. 

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. 

“This shows that water stress and eutrophication are not good indicators for locating threatened species and should not be used to guide conservation. Instead, it is essential that freshwater species data are actively included in conservation strategies and water use planning and management, to ensure their practices support healthy freshwater ecosystems,” said Dr Topiltzin Contreras MacBeath, Co-Chair of the IUCN SSC Freshwater Conservation Committee. “Increased investment in measuring and monitoring freshwater species is needed to ensure conservation action and water use planning is based on the latest information.” 

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. 

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

“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,” said Catherine Sayer, IUCN’s Freshwater Biodiversity Lead and lead author on the paper.  

“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 IUCN World Conservation Congress this October will 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 on the ground to plan freshwater conservation measures where they are most needed.”