A quarter of the world’s freshwater fauna, including fish, dragonflies, crabs, and shrimps, face a high risk of extinction, according to a study co-authored by the International Union for Conservation of Nature (IUCN) and published in the science journal Nature on Wednesday.
The study, the result of over 20 years of work by more than 1,000 experts from around the world, reached its conclusions after analysing 23,496 freshwater species on the IUCN Red List. It is the largest global assessment of its kind to date.
“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 the paper’s lead author. The study’s findings revealed that at least 4,294 species are at high risk of extinction. Crabs, crayfish, and shrimps are at the highest risk (30%), followed by freshwater fishes (26%) and dragonflies and damselflies (16%). Alarmingly, 89 freshwater species have already gone extinct since 1500, with another 187 likely extinct but awaiting confirmation.
Western Ghats most affected
Freshwater ecosystems, though covering less than 1% of the Earth’s surface, are home to 10% of all known species on Earth. However, they are vanishing at an alarming rate. Nowhere is this loss more profound than in the Western Ghats, a freshwater biodiversity hotspot and home to many endemic species. The study identifies this region as one where freshwater species are most threatened.
“There are over 300 species of freshwater fish in the Western Ghats. More than half of them are found only here and nowhere else on Earth, making them exceptionally vulnerable to environmental threats,” said Dr Rajeev Raghavan, assistant professor at the Kerala University of Fisheries and Ocean Studies (KUFOS), Kochi. According to him, Kerala has the highest number of threatened freshwater fishes in India (74), and the Periyar River is the most significant in terms of ‘conservation attention’ as it harbours the maximum number of endemic and threatened freshwater fishes in Kerala.
Other highly affected regions identified in the study include Lake Victoria in Africa, Lake Titicaca in South America, and Sri Lanka’s Wet Zone.
Environmental threats and the way forward
Pollution tops the list of threats, affecting 54% of at-risk freshwater species. Agriculture and urban development exacerbate the problem, with pesticides, fertilisers, and untreated wastewater flowing unchecked into rivers and lakes. Dams and water management projects, which alter natural flow regimes and block migratory routes, are the second-largest threat, impacting 39% of species. Invasive species, overharvesting, and climate change further compound the challenges.
According to Dr Rajeev, conservation strategies designed for iconic terrestrial species, such as tigers and elephants, do little to benefit freshwater species in shared habitats like the Western Ghats. For instance, the critically endangered humpbacked mahseer (Tor remadevii), a mega fish that can grow up to 60 kg, is severely threatened by habitat loss.
“Protecting freshwater fauna requires tailored interventions, such as restoring river ecosystems, regulating fishing, and preventing the spread of invasive species,” said Rajeev, who is also the South Asia Chair of the IUCN SSC Freshwater Fish Specialist Group and a co-author of the paper.
The authors also stress the importance of incorporating freshwater species data into broader conservation strategies. “Freshwater ecosystems are not resources for exploitation; they are lifelines for humanity. Saving them will require bold, collective action across disciplines, sectors, and borders. Our health, nutrition, drinking water and livelihoods depend on them,” added Stephanie Wear, Conservation International Senior Vice President at the Moore Center for Science.
The full article is available at: https://icsf.net/resources/one-quarter-of-freshwater-fauna-threatened-with-extinction-by-catherine-a-sayer-et-al-2025/