The absence of a comprehensive strategy to arrest the wild growth of invasive alien plants in the forest areas of the Nilgiri Biosphere Reserve, including the Wayanad Wildlife Sanctuary (WWS), poses a threat to wildlife habitat.
Apart from the spread of Manjakkonna ( Senna spectabilis ) and exotic plants such as Elappullichedi ( Hypoestes phyllostachya ) and Kudamaram or Umbrella Tree ( Maesopsis eminii ), Dhritharaashtra pacha (Mikenia micrantha ), Arippoo/konginippoo ( Lantana ) and Communist pacha ( Eupatorium ) are also posing a serious threat to the region, a major habitat of Asiatic elephants, tigers and other wildlife population in the country. Senna spectabilis is more dangerous than other exotic species owing to its quick growth, a Forest Department source said.
Nearly 3,000 sq km of the region, including three forest divisions in Wayanad contiguous with the Nagarhole National Park and the Bandipur Tiger Reserve in Karnataka and the Mudumalai Tiger Reserve in Tamil Nadu, has wild growth of the invasive plant. Earlier, grazing of herbivores, including spotted deer, on the grassland near the forest range offices at Tholpetty and Muthanga was a usual sight, but after the spread of the plant, the sighting has become rare.
A survey conducted by the Wildlife Trust of India (WTI), in association with the Forest Department, has revealed that the plant is widely distributed in the Muthanga, Kurichiyad and Tholpetty range of forests under the sanctuary. Taking clues from the studies conducted in various parts of the world and based on the recommendations from research institutions like Kerala Forest Research Institute (KFRI), the sanctuary management has been trying out several control measures to eradicate the plant, but without the desired result.
Last year, Manjakkonna trees on a hectare of forestland in the Muthanga range of the sanctuary was uprooted using an excavator, but the tree started to regenerate from the remaining roots this monsoon.
T. K. Hrideek, scientist, KFRI, told The Hindu that girdling of the plant was the only effective method to arrest its spread, but many a time the workers failed to perform the work properly owing to allergy to the allelopathic properties of Manjakkonna. The KFRI has been experimenting with other control measures also to eradicate the invasive species, Dr. Hrideek said.
N. Badusha, president, Wayanad Prakruthi Samrakshana Samiti, said the quick spread of the invasive plants leads to food shortage for wildlife population, especially herbivores. This would worsen the human-animal conflict in the region. As the forest areas of Tamil Nadu and Karnataka, adjacent to Wayanad, were also faced with the same threat, the two State governments would do well to put pressure on the Union Ministry of Environment, Forests and Climate Change to allot more funds to tackle the issue, he added.