by Alolika Sinha
The grasslands of Manas National Park
Photo: Udayan Borthakur
The grassland ecosystems are one of the most productive ecosystems in the world which usually supports very high vertebrate biomass. The grassland of Manas National Park is one of the few remnant patches of grassland habitat in western Assam. It has diverse assemblage of grass and other plants pecies and supports many globally threatened and grassland specialist species like pygmy hog, one-horned rhinoceros, Asiatic wild buffalo, hispid hare, hog deer and Bengal Florican. But over the years, these potential habitat is shrinking and affected by various factors resulting in its degradation. Of many factors, spread of alien invasive plant species is considered as the biggest threat to the grassland of Manas. With the continuous grassland habitat degradation, we may lose our important and rare grassland obligate faunal species besides others in no time. In India, most of the conservation actions are species specific and not much attention is given to the habitats they live in. It is high time that we should implement habitat conservation strategy for the benefit of multiple-species conservation. In one such effort, Aaranyak in collaboration with the forest department and BTC has initiated a habitat improvement project in Manas National Park targeting the control of spread of invasive plant species in the grasslands.
By definition, a species is termed as invasive when it is introduced to the environment and have negative effect on environment, economy and human health. An invasive species can be both native or alien. The infestation by this invasive species is considered as the second biggest threat to biodiversity only after habitat destruction. A survey, conducted during 2014 and 2015 identified two invasive plant species that are widespread in the grassland of Manas are Chromolaena odorata and Mikania micrantha. These are perennial plants native to central and South America and are listed among the “100 worst invasive species” list by IUCN.These plants are often allelopathic and can smother other plants in the vicinity.
In India, Chromolaena odorata was first introduced to Kolkata in 1845 as an ornamental plant. Soon this formidable weed escaped to the forests and the agricultural areas which is eventually outcompeting the native species. Given the rate at which it is spreading and replacing the grasses in Manas; management intervention is must to arrest this.
Controlling the infestation