The most extensive global assessment of freshwater animals to date has revealed that a quarter of all freshwater animal species on the IUCN Red List are threatened with extinction.
The largest number of these threatened species are found in East Africa’s Lake Victoria, South America’s Lake Titicaca, Sri Lanka‘s Wet Zone, and India’s Western Ghats mountain range, the new study found.
Researchers evaluated 23,496 species of freshwater fish, dragonfly, damselfly, crab, crayfish and shrimp, and found that 24%, are threatened with extinction. This means one in four freshwater specie are categorized as either extinct in the wild, critically endangered, endangered, vulnerable, or near threatened. These include the daisy burrowing crayfish (Fallicambarus jeanae) in Arkansas and the European eel (Anguilla anguilla).
“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,” study lead author Catherine Sayer, the IUCN’s freshwater biodiversity lead, said in a statement.
The study found that among the freshwater animals they studied, 30% of decapods, which include crabs, crayfishes and shrimps, are at the highest risk of extinction, followed by 26% of freshwater fish and 16% of dragonflies and damselflies.
Additionally, 89 of the assessed species have gone extinct since 1500 C.E. Of these, 22 were found in the U.S., and 15 each in Mexico and the Philippines. All 15 from the Philippines were from Lake Lanao, one of the world’s most ancient lakes. One of them was the bitungu (Barbodes truncatulus), known for its peculiar overbite and for being a local food delicacy.
“The true number of extinctions of freshwater species will probably be higher given the overall lack of research on and long-term monitoring of freshwater biodiversity,” the study notes.
The loss of freshwater habitats to agriculture and urban development, overharvesting, invasive species, pollution, dam construction and water extraction emerged as major threats to freshwater species.
In the Western Ghats, for example, the critically endangered humpbacked mahseer (Tor remadevii) “is threatened by habitat loss due to river engineering projects and sand and boulder mining, poaching and invasive alien species,” study co-author Rajeev Raghavan, South Asia chair of the IUCN’s Freshwater Fish Specialist Group, said in the statement.
Iwan Jones, a freshwater ecologist from Queen Mary University of London, who wasn’t involved in the study, wrote in The Conversation that “many of the freshwater species considered in this study are socially and economically important.”
“The widespread decline in these species reflects increasing pollution and other pressures, which does not bode well for our society in the face of climate change and diminishing water availability,” Jones added.
The study’s authors urge increased investment in research to address data deficiency, particularly in groups like freshwater mollusks.
This article by Kristine Sabillo was first published by Mongabay.com on 14 January 2025. Lead Image: Discus fish by Rhett A. Butler/Mongabay.
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