Freshwater ecosystem in Western Ghats under strain

everal freshwater species of fish, invertebrates, dragonflies, damselflies and aquatic plants in the Western Ghats may soon become extinct because of water pollution from agricultural and urban sources, overfishing and invasive species. According to a study by Zoo Outreach Organisation, Coimbatore, and International Union for Conservation of Nature (IUCN), the world’s foremost authority on threatened species, at least 16% of the 1,146 freshwater species face extinction. Globally too, freshwater fish are the most susceptible group with more than a third (37%) of the 290 species at risk.

Among the vanishing species is the Deccan mahseer (tor khudree), one of the most sought-after fish in peninsular India. Over-harvesting, invasive species and pollution have led to a drastic fall in its numbers.

Miss Kerala (Puntius denisonii), another fish species, is being collected indiscriminately for ornamental trade and its habitat is being impacted by water pollution from plantations and urban areas. Land-use change has affected nukta, a fish found near Mhalunge along the Indrayani river as industrialization has claimed some portion of the water body.

The comprehensive research, called Western Ghats freshwater biodiversity assessment project, was taken up by over 50 experts, including taxonomists, researchers and ecologists. Several experts from Pune were involved in this assessment.

The study that began in January 2010 looked at the conservation status and distribution of all freshwater species in the Western Ghats in Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu and the associated river systems.

The findings are stark. Of the 600 species of aquatic plants in the Western Ghats, 10% are threatened, while 12% of the 77 species of molluscs and 4% of the 170 species in dragonflies and damselflies suffer the same fate.

Of the 290 fish species, 37% are threatened. While 50% of these are endemic, more than 60% are threatened. These species are on the IUCN’s red list – a comprehensive inventory of the global conservation status of plant and animal species.

The baseline data will help experts take up conservation measures. Researcher Aparna Watve told TOI that many communities are dependent on these freshwater species for livelihood.

“More than half of all fish and 18% of all mollusc species in the region are used as food. Aquatic plants have a diverse range of uses, with 28% of species providing valuable medicinal resources,” she said.

Many species are not found anywhere in the world which necessitates their indepth study and documentation. “Of the 1,146 species assessed in this project, 120 are data deficient,” she said.

Cremnochonchus syhadrensis, an endangered freshwater mollusc, is found only in the northern Western Ghats.

“Pollution and water abstraction have affected its numbers,” said researcher Neelesh Dahanukar.

Dahanukar, a fellow of the Indian Institute of Science Education and Research, Pune, said the species is highly habitat-specific, found only in the spray zones of waterfalls, and hibernates in rock crevices during the summer.

“Recent surveys have failed to find the species in one of its few remaining locations,” he added.

Aquatic plants like the aponogeton satarensis are also affected. This herb species is found in a few temporary pools in the Kaas plateau in Maharashtra. However, it is being impacted by development of windmills and increasing tourism.

Experts have said that areas rich in biodiversity must be declared as protected. Conservation efforts by a network of NGOs, experts, researchers and academicians of freshwater species are among the recommendations to be submitted to the ministry of environment and forests.

IMPACT

Pollution is the main threat impacting freshwater biodiversity in the Western Ghats

Urban and domestic pollution are the worst threats followed by agricultural and industrial sources of pollution

Residential and commercial projects pose a threat to 14% of fish, 11% odonates and aquatic plants, and 8% molluscs

Dams and other natural system modifications impact 13% of fish, 8% molluscs, 4% odonates and 3% plants

Invasive species impact 22% of fish

Agriculture and aquaculture projects impact 7% of odonates and 4% of plants

Energy production and mining impact 6% of fish, 5% molluscs and 4% plants

RECOMMENDATIONS

To take up studies, survey and monitoring and restore habitat, control pollution and manage invasive species management

Environmental impact assessment of development activities, awareness and education outreach, legislation and enforcement and identify key biodiversity areas

OTHER SUGGESTIONS

Construction of large dams should be avoided where adverse impacts to freshwater species and the services provided are predicted

Mining and quarrying should be regulated

Threatened and endemic species of freshwater fish of biological and socio-economic importance should be included within the Indian Wildlife (Protection) Act

Policies should also be developed for conservation of lesser-known invertebrate groups such as molluscs, dragonflies, damselflies and crustaceans

WHY ‘THREATENED’

Species listed as critically endangered (close to extinction), endangered or vulnerable are collectively described as ‘threatened’. Threatened is categorized on the basis of area (distribution), threats and population

The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List), founded in 1963, is the world’s most comprehensive inventory of the global conservation status of plant and animal species.

Source: Times of India

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