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
The ever-increasing and thriving invasive plants in Manas has raised concern among the park managers and conservationists. Aaranyak took up the work and set-up some experimental plots and each of these plots were subjected to different treatments- cutting, cutting and burning and uprooting the invasive plants. Of these three treatments, manual uprooting of the invasive plants was the best method to control it. But it is easier said than done. Manual uprooting is resource-hungry and need a great amount of commitment for longer period of time. Nevertheless, to ensure that grass remains greener in Manas, we have to get rid of these invasive plants. We have successfully demonstrated an experimental plot of 1 ha area, wherein the invasive plants were first uprooted and then burned. The uprooting was done prior to flowering, to minimise the dispersal of seeds. This plot was fenced to protect it from grazing and the activity was continued for three consecutive years. This led to the growth of lush green grasses of the association Imperata-Sachharum-Narenga-Cymbopogon. With the grass, came in the animals too.
On successful demonstration of grass re-growth, the park managers and other organisation working in the landscape are keen to take-up the work. This resulted in organising a habitat management workshop where both the frontline staffs and the organisations actively participated. The organisations will work collaboratively to restore the degraded grassland patches in the park for the benefit of grassland and its depended fauna. And as I said, pull the weed and the grass will be greener!
*Article republished from The Assam Tribune 4th February 2018.
About the Author:
Alolika Sinha is a wildlife biologist working with Aaranyak. Her research interest lies in herbivore-habitat interaction and community conservation.