Four in 10 species inhabiting inland water ecosystems in the Western Ghats face the threat of extinction, conservation scientists said on Wednesday after a worldwide assessment covering habitats critical to livelihoods and the environment.
The assessment by an international consortium of researchers has estimated that 24 per cent of freshwater fauna worldwide are threatened with extinction, with at least 4,294 of the 23,496 freshwater animals at high risk of extinction.
The freshwater species under threat of extinction include fish, crabs, crayfishes, shrimps, dragonflies and damselflies, among others, the researchers said in a study published on Wednesday in the journal Nature.
The Devario neilgherriensis, an endangered species found only in the streams flowing through the Nllgiri Hills. Picture: Dencin Thampy
Lake Victoria in Africa, Lake Titicaca in South America and the Western Ghats are among areas with the greatest numbers of these threatened species. In the Western Ghats, 124 (41 per cent) of the 301 freshwater species assessed face an extinction risk.
Among the Western Ghats’ threatened species are the hump-backed mahseer found only in the River Cauvery, the subterranean groundwater dragon snakehead fish, and the peninsular hill trout, found only in the River Periyar.
“Elephants and tigers in the Western Ghats live side by side with the critically endangered hump-backed mahseer,” said Rajeev Raghavan, assistant professor at the Kerala University of Fisheries and Ocean Studies, Kochi, and a study co-author.
“But conservation efforts for tigers and elephants will not help the mahseer, which faces multiple threats.”
The hump-backed mahseer is a megafish that grows up to 60kg. Scientists estimate that its population has declined by over 90 per cent in the past three decades under pressure from habitat loss caused by river engineering projects, sand and boulder mining, poaching and the proliferation of non-native species.
The Lambuca fasciata, a threatened species of fish from the Western Ghats. Picture: Beta Mahatvaraj
"Many freshwater fish in the Western Ghats have a small geographic distribution — they’re found in a single river or at a single location. This makes them even more vulnerable to the risk of extinction," Raghavan told The Telegraph. "If they vanish from the Western Ghats, they’ll be lost to the world."
In the Western Ghats, growing populations of non-native fish such as the African catfish, common carp, or tilapia too pose a threat to native fish, he said.
The study found that among the groups studied, 30 per cent of crabs, crayfishes and shrimps are at risk of extinction, followed by 26 per cent of freshwater fishes and 16 per cent of dragonflies and damselflies.
Of the freshwater species under threat, 54 per cent are threatened by pollution, 39 per cent by dams and water extraction, 37 per cent by agriculture and other land use changes, and 28 per cent by invasive species and diseases.
Freshwater species' richness is highest in the tropics, with concentrations in the Amazon basin in South America; in western, central and eastern Africa; and tropical Asia — from southern India and southeastern Asia to New Guinea.
“Lack of data on freshwater biodiversity can no longer be used as an excuse for inaction,” the study’s lead author, Catherine Sayer of the International Union for Conservation of Nature (IUCN), said in a media release.
Freshwater landscapes are home to 10 per cent of all known species on Earth and key to billions of people’s access to safe drinking water, livelihood and flood control, among other benefits, Sayer said.
Raghavan, South Asia chair of the IUCN fish specialist group, said many freshwater species played key roles in the economy and the environment.
“They provide livelihoods to people in inland water landscapes and also help recycle nutrients, disperse seeds, (and) serve as prey to other animals.”