One in Four Freshwater Animal Species Faces Extinction Risk: Study

A quarter of all freshwater animals, including crustaceans, fish and insects, face a high risk of extinction from threats like pollution, farming and dams, a new study has found.

Rivers, lakes, wetlands and other bodies of freshwater cover a relatively small amount of Earth’s surface — less than one percent — but are home to more than 10 percent of the planet’s known species, including a third of vertebrates and half of fish, reported AFP.

“Freshwater ecosystems are highly biodiverse and important for livelihoods and economic development, but are under substantial stress. To date, comprehensive global assessments of extinction risk have not included any speciose groups primarily living in freshwaters,” the authors of the study wrote. “Here we present the results of a multi-taxon global freshwater fauna assessment for The IUCN Red List of Threatened Species covering 23,496 decapod crustaceans, fishes and odonates, finding that one-quarter are threatened with extinction. Prevalent threats include pollution, dams and water extraction, agriculture and invasive species, with overharvesting also driving extinctions.”

Roughly 30 percent of decapods — like crabs, shrimp and crayfish — were found to be at risk, compared with 16 percent of odonates such as dragonflies, 23 percent of tetrapods like reptiles and frogs and 26 percent of fish, AFP reported.

Since the year 1500, 89 freshwater species are known to have become extinct, with an additional 178 suspected to have ceased to exist. The study’s authors said the figures are likely underestimated since there is so little information about certain species.

“Most species don’t have just one threat putting them at risk of extinction, but many threats acting together,” said Catherine Sayer, an International Union for Conservation of Nature zoologist who was co-author of the study, as reported by The Associated Press.

The study said that, between 1970 and 2015, 35 percent of wetland area had been lost.

There “is urgency to act quickly to address threats to prevent further species declines and losses,” the authors wrote in the study.

According to the findings, approximately a third of rivers more than 620 miles long are no longer free-flowing throughout their full length.

“Until recently, the freshwater realm has not been given the same priority as the terrestrial and marine realms in global environmental governance,” the authors wrote.

Stuart Pimm, a Duke University ecologist who did not contribute to the study, called the findings “hugely important,” The Associated Press reported.

“Almost every big river in North America and Europe is massively modified” by dams, which put freshwater species at risk, Pimm said.

South America’s Amazon River ecosystem is under threat from deforestation, illegal gold mining and wildfires, Charvet said. Forest clearing through illegal burning produces ash that ends up in the river, while mercury gets dumped into the water by unlicensed goldminers, Charvet explained.

Wetlands and rivers “concentrate everything that happens around them,” Charvet added. “If something goes really wrong, like an acid or oil spill, you can threaten an entire species. There’s nowhere else for these animals to go.”