New Delhi: The Western Ghats mountain range, one of India’s four biodiversity hotspots, is among the four regions in the world where freshwater species are most threatened with extinction, as per a recent study published in the journal Nature on January 8.
The study, which is the largest global assessment of freshwater animals on the International Union for Conservation of Nature’s (IUCN’s) Red List of Threatened Species so far, shows that 24% of the world’s freshwater fish, dragonfly, damselfly, crab, crayfish and shrimp species are at high risk of extinction. Established in 1964, the IUCN Red List assesses the global conservation status of animal, fungus and plant species and lists them into nine categories based on their assessment levels and how threatened by extinction they are, based on criteria such as population declines, restricted ranges and more. These are “Extinct,” “Extinct in the Wild,” “Critically Endangered,” “Endangered,” “Vulnerable,” (the latter three list species threatened with global extinction in decreasing order of threats) “Near Threatened,” (which comprises species that will be threatened without ongoing conservation measures), “Least Concern,” (species that have a lower risk of extinction) “Data Deficient” (species whose conservation status cannot be assessed because of insufficient data) and “Not Evaluated.”
Key findings: Regions and species most threatened
The recent study found that at least 4,294 species out of 23,496 freshwater animals on the IUCN Red List are at high risk of extinction. Crabs, crayfishes and shrimps are at the highest risk of extinction of the groups studied, with 30% of all these species being threatened, followed by 26% of freshwater fishes and 16% of dragonflies and damselflies. And the greatest number of threatened species dwell in Lake Victoria (distributed across the African countries of Tanzania and Uganda, and on the border of Kenya), Lake Titicaca (in the Andes mountain range bordering Peru and Bolivia), Sri Lanka’s Wet Zone (in the central and southwestern region of the island nation) and the Western Ghats of India. The threatened species in the Western Ghats include the Saffron reedtail (Indosticta deccanensis), a dragonfly that is found only in some localities in the mountain range and is considered “Vulnerable” by the Red List, and the Dwarf Malabar Puffer (Carinotetraodon travancoricus), a species of freshwater puffer fish found in some streams of the Ghats and is “Data Deficient.” However, species like the Kani maranjandu, a spider-like tree crab discovered from the southern Western Ghats in Kerala in 2017, are not even currently assessed in the Red List – there is no data on its conservation status at all.
The reasons for freshwater species being the most threatened in these regions including the Western Ghats are not ones we are unfamiliar with – pollution, mainly from agriculture and forestry, impacts over half of all threatened freshwater animals, according to the study. Add to this land conversion for agricultural use, water extraction and the construction of dams, which also block fish migration routes. Other reasons also include overfishing and the introduction of invasive alien species.
Case study: The hump-backed mahseer
The study also found that although the threatened freshwater animals studied tend to live in the same areas as threatened amphibians, birds, mammals and reptiles, they face different threats due to their specific habitats. Conservation action must therefore be targeted to these species, the study recommends. Take the case of the “Critically Endangered” hump-backed mahseer (Tor remadevii) that is found only in the river system of the Cauvery and its tributaries in south India, for instance. The fish, once thought to be widespread across the entire river (as per historical records dating back to the late 19th century), is now found in just five fragmented river and tributary stretches of the Cauvery, which is a shocking decline of around 90% in its distribution range, according to the IUCN Red List assessment.
“Although they live side by side in the Western Ghats, conservation action for tigers and elephants will not help the ‘Critically Endangered’ hump-backed mahseer, which is threatened by habitat loss due to river engineering projects and sand and boulder mining, poaching and invasive alien species. Active protection of the river and tributaries where the hump-backed mahseer lives is essential to its survival, in addition to fishing regulations and banning the introduction of further invasive alien species,” noted Rajeev Raghavan, South Asia chair of the IUCN Species Survival Commission Freshwater Fish Specialist Group and one of the co-authors of the study, in a press release.
The study also found that water stress and eutrophication are poor “surrogates,” or indicators, to be used in conservation planning for threatened freshwater species; areas with high water stress, where there is high demand and low supply, and areas with more eutrophication, where an excess of nutrients in the water leads to overgrowth of algae and plants, are home to fewer numbers of threatened species than areas with lower water stress and less eutrophication.
The study recommends targeted action to prevent further extinctions and calls for governments and industry to use this data in water management and policy measures. “Lack of data on the status and distribution of freshwater biodiversity can no longer be used as an excuse for inaction,” the study read.
The hump-backed mahseer, for example, badly needs a systematic conservation plan, Raghavan told The Wire. Despite being a “Critically Endangered” species (tigers across the world, in comparison, are only “Endangered” as per the IUCN Red List) and one of India’s mega fish as well as a transboundary species (found in tributaries of the Cauvery in Kerala, Karnataka and Tamil Nadu), there have been no efforts to develop a conservation plan for the species yet, Raghavan said.
“Protection of critical habitats is the most important strategy. There is also need for some more research, as very little information is available on the ecology, movement and early life history of the species,” he added. “This could be a nice example of a flagship species that can bring all three states together (especially as a positive side to the Cauvery water dispute)… securing the future of this species requires an effort from all three states.”
Global implications and call to action
“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,” stated Catherine Sayer, IUCN’s freshwater biodiversity lead and lead author of the paper, in a press release. “The IUCN World Conservation Congress this October will guide conservation for the next four years, as the world works to achieve the Sustainable Development Goals and the Kunming-Montreal Global Biodiversity Framework targets by 2030. This information will enable policy makers and actors on the ground to plan freshwater conservation measures where they are most needed,” she added.
“This report really drives home just how under threat freshwater species are globally as a result of human activities,” noted co-author Matthew Gollock, Zoological Society of London’s programme lead for aquatic species and policy and chair of the IUCN Anguillid Eel Specialist Group, in a press release. “The good news is, it’s not too late for us to tackle threats such as habitat loss, pollution and invasive species, to ensure our rivers and lakes are in good condition for the species that call them home.”
Note: This article, first published at 9.32 am on January 13, 2025, was republished at 8.20 am on January 14, 2025.
