Invasive species, a big threat to biodiversity

After habitat destruction, ‘invasive alien’ species is proving to be the biggest threat to biodiversity in the Nilgiris Biosphere Reserve. But state authorities are yet to realise the fact.
In a recent investigation, Prof VS Ramachandran of Bharathiar University found that 223 species of angiosperms (flowering plants) belonging to 56 families have naturalised in the Nilgiris Biosphere Reserve alone.
Invasive alien species are plants that are not endemic to a place. For instance, a croton variety found in Kalakkadu Mundanthurai Tiger Reserve in Tirunelveli district in 1991 was found to have come from Vavuniya along with the Tamil militants who used the forests for training, says a forest officer.
With the increase in number of alien plant species and their density in the bio-reserve, research and knowledge on alien species are required to assist in the development of effective control strategies, says V S Ramachandran, a professor of botany.
From previous studies, Ramachandran found that an orchid and two types of grass species show different types of growth under the native habitat (shola forests and open grasslands) and a habitat dominated by an invasive species (eucalyptus and wattle). While the growth was 40–45 cm in the former, it was 15 cm in the eucalyptus forest.
New roads are the most common reason for introduction of alien species resulting in loss of species and sometimes even extinction of a few plants. In Mudumalai forests, lantana camara, an obnoxious weed, spread like wild fire, obstructing the growth of other plants. Such invasive weeds also curb the movement of animals, says S Jeyachandran, secretary, Tamil Nadu Green Movement.
The eco-activist, based in Udhagamandalam, charges that the forest department has had no lantana eradication programme in its working plans over the years. Only now, the field director of Project Tiger has taken up the task of clearing the exotic plant that has invaded into the core zone of the tiger reserve.
According to scientists and activists, forest managers in Rajasthan have used a spray to stop the spread of lantana. In Himachal Pradesh, furniture is being made from twigs of lantana. “The invasiveness of lantana is a national issue. The Tamil Nadu government must first realise the destruction of forest habitat due to invasive plants. Only then, there can be an eradication programme,’’ says K Kalidas, president, OSAI, an NGO.