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 on Wednesday, January 8, 2025.
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.
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.
“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.”
The study, “One quarter of freshwater fauna threatened with extinction”, 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.
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.
Dr Topiltzin Contreras MacBeath, Co-Chair of the IUCN SSC Freshwater Conservation Committee, said: “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. 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.
The global freshwater fauna assessment is said to be the result of over 20 years of work by more than 1,000 experts from around the world.
Tim Lyons, Director of Conservation at New Mexico BioPark Society, said: “These landmark findings are a rallying cry around freshwater species and the declining habitats that support them. Historically, the important role of freshwaters in safeguarding global biodiversity has been overlooked, and key differences in how these systems should be managed are only now being recognised.
“It is imperative that conservation actors work collaboratively to address the challenges of pollution, shortsighted habitat modification, and the spread of invasive species head on. The solutions to these threats may be novel and innovative, and the data presented here can be used as a roadmap to guide our collective efforts.”
Stephanie Wear, Conservation International senior vice president at the Moore Center for Science, said: “It’s easy to see that freshwater ecosystems have been under extreme stress as drinking water becomes limited, droughts intensify and pollution seeps into these habitats. To learn that a quarter of the world’s freshwater species are at high risk of extinction as a result is a deeply troubling trend. This science shows what we already feared to be true – freshwater ecosystems and the species that live within them need immediate help.
“Most threatened freshwater animals like shrimps, crayfish and crabs are small, living unseen beneath the surface but no matter their size, they are essential for keeping healthy the ponds, lakes and rivers that billions of people rely on. Environmental degradation is a risk to their survival and our own. We must take this news seriously and rather than despair, invest energy and resources into conserving these environments – our health, nutrition, drinking water and livelihoods depend on them.”
Malin Rivers, Head of Conservation Prioritisation at Botanic Gardens Conservation International, said: “This study underscores the urgent situation of freshwater ecosystems, with biodiversity facing significant risk of extinction and requiring immediate conservation intervention. It is important to address the principal threats and take targeted conservation action to mitigate further decline. Safeguarding the broader freshwater habitat, including both animals and plants, is crucial to ensuring the continued provision of essential ecosystem services for those who rely on these landscapes.”
Anne Bowser, CEO of NatureServe, said: “The finding that one quarter of freshwater animals are at risk of extinction is a stark reminder of the urgent challenges we face in protecting biodiversity. This underscores how essential high-quality, accessible data is for identifying at-risk species and taking action to conserve them. By prioritising data-driven strategies, we can make more informed decisions to safeguard freshwater ecosystems and the species they support.”
Chouly Ou, freshwater fish conservation coordinator at Re:wild, said: “Freshwater ecosystems and the species they support are often taken for granted, but they are critical to preventing biodiversity loss and securing livelihoods. As we learn more about species living in freshwater habitats around the world, it’s clear that we need to scale efforts to protect them. Re:wild is a partner of SHOAL, a global alliance dedicated to supporting local partners across the world to prevent the extinction of freshwater species, which is a great example of what scaling conservation efforts could look like.”
Dr Matthew Gollock, ZSL’s Programme Lead for Aquatic Species and Policy, and Chair of the IUCN Anguillid Eel Specialist Group, said: “This report really drives home just how under threat freshwater species are globally as a result of human activities. The good news is, it’s not too late for us to tackle threats such as habitat loss, pollution and invasive species, to ensure our rivers and lakes are in good condition for the species that call them home.”
