DR Ambedkar IAS Academy

Himalayan knotweed latest threat to Nilgiris ecosystem

One of the most recent invaders of the landscape — a knotweed native to the Himalayas — has begun taking root in the upper slopes of the Nilgiris, potentially threatening biodiversity along streams and rivers.

The knotweed, known as Polygonum molle (Sikkim knotweed), which has been recently reclassified as Koenigia mollis, has begun spreading along many streams and rivulets in the upper Nilgiris, especially around Doddabetta, Kodappamund, Adasolai and the Ketti Valley, conservationists here say.

The plant has spread to the Nilgiris only over the last couple of decades, conservationists said, adding that the rate at which they seem to be spreading is a serious cause for concern.

Shiny Mariam Rehel, programme co-ordinator, Biodiversity Restoration Programme at Keystone Foundation and a botanist, said the knotweed was among 27 different species of invasive flora identified by them to pose a threat to native landscapes and biodiversity in the Western Ghats.

“We notice that though these plants typically grow along the sides of streams and rivers, they seem to also now be spreading to the sides of the road, meaning they can be even more quickly spread to other locations,” said Ms. Rehel. She added that as the knotweed grows, it can cover huge expanses of land, leaving little to no space for other native plant species to grow.

“The wetlands in the Nilgiris are under threat from various factors, including the knotweed. The spread of such invasive species should serve as a wake-up call to spur us into acting to protect these wetlands,” she said.

Conservationists believe that the knotweed could have been brought to the Nilgiris by visitors and accidentally released into the landscape.

Godwin Vasanth Bosco, a restoration ecologist and a member of the High Court-appointed expert panel on invasive species management, said the knotweed was one of the newest species of flora found to be expanding in the region rapidly. “There are at least a hundred more plant species that have been introduced onto the plateau that have found a place in the altered ecology,” he said.

When contacted, a senior forest official said the department was aware of the problem but wattle and eucalyptus were the primary focus areas of invasive removal at present.

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