Study documents extinction threats to world’s freshwater species
WASHINGTON — Freshwater environments cover about 1% of Earth’s surface while accounting for more than 10% of known species. Like many marine and terrestrial ecosystems, however, they are in distress. A new study looking at some of the denizens of freshwater habitats offers a stark illustration of this biodiversity predicament.
Researchers assessed the status of 23,496 species of freshwater animals in groups including fishes, crustaceans such as crabs, crayfish and shrimp and insects such as dragonflies and damselflies, finding 24% of them at a high risk of extinction.
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“Prevalent threats include pollution, dams and water extraction, agriculture and invasive species, with overharvesting also driving extinctions,” said conservationist Catherine Sayer, lead author of the study published on Wednesday in the journal Nature.
Sayer heads the freshwater biodiversity unit at the International Union for Conservation of Nature (IUCN), the organization that tracks the status of species globally.
Some of the freshwater species deemed at high risk bear exotic names such as the mini blue bee shrimp of Sulawesi, the Seychelles duskhawker dragonfly, the Atlantic helicopter damselfly of Brazil, the daisy burrowing crayfish of Arkansas and fishes such as the shortnose sucker of Oregon and California and the humpbacked mahseer of India.
The study filled a gap in data on freshwater biodiversity. The studied species were selected because their diverse positions within food webs present a holistic view of the health of freshwater ecosystems globally.
These species inhabit inland wetlands such as lakes, rivers, swamps, marshes and peatlands – areas that the researchers said have been reduced by more than a third since 1970. Other research has documented the status of mammals, birds, reptiles and amphibians that share these freshwater ecosystems and often face their own unique threats.
Of the animal groups investigated in the new study, the highest threat levels were documented in the crustaceans (30% threatened) followed by the fishes (26%) and the dragonflies and damselflies (16%).
