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.

Sathyamangalam may become tiger reserve

As the magnificent big striped cats are being repeatedly spotted in the Sathyamangalam sanctuary, the state government will soon take efforts to turn it into a tiger reserve. Last week, there were as many as five direct sightings during an official survey.

In the six-day carnivore sign survey taken up by the state forest department, five tigers were directly sighted by foresters and volunteers involved in the census in Hasanur and Bhavanisagar ranges of Sathyamangalam forest division, adjoining the Mudumalai and Bandipur tiger reserves. The survey team has also found evidence that there could be four more tigers roaming these forests. When state forest minister N Selvaraj visited Sathyamangalam, the division’s forest officials briefed him on the need to make it a tiger reserve as there was solid and clinching evidence that the tigers have made the scrub jungles their home over the past few years. “Yes, I was told about the importance of Sathyamangalam forests and the need to make it a tiger reserve. We will certainly consider it,” Selvaraj told TOI.

Sathyamangalam forests link the Eastern and Western Ghats allowing gene flow between diverse populations of the two habitats. Incidentally, the Karnataka forest department has sent a proposal to make Biligiri Rangaswamy (BR) Wildlife Sanctuary, contiguous to Sathyamangalam, as a tiger reserve, officials note.

Tamil Nadu already has three tiger reserves in Kalakad-Mundanthurai, Mudumalai and Anamalai. Sathyamangalam which has been in the spotlight for the past five years for sighting of tigers could be the fourth.

Interestingly, tigers were sighted in Kodaikanal forests after a long time during the sixday survey that concluded on Thursday. A tigress and her cub were spotted playing in the wild. The forest officials are sifting through columns of data scouring for clear evidence to work out an estimate of the tiger numbers based on indirect evidence like pug marks, scats and scratches.

Tigers burning bright in western ghats

It is not official yet, but the news that there has been direct sighting of 30 tigers over six days along the Western Ghats in the state during the latest carnivore sign survey is quite encouraging. At the end of the six-day survey which concluded on February 25, forest officials, wildlife enthusiasts and volunteers who ventured out into the forests for the survey are quite thrilled by its outcome.

Rajiv K Srivastava, field director Mudumalai Tiger Reserve, said, “The feedback and the inputs from the volunteers give a very good indication of a healthy tiger population in the reserve. It is encouraging. The number of tigers is growing.’’ In 2006, there were an estimated 38 tigers in Mudumalai but this time the forest officials expect more.

The six-day census was conducted by the forest department in coordination with the Nilgiris Wildlife and Environment Association (NWEA). “We are participating in a wildlife census for the first time. We saw bears, leopards, sambars, gaur, bison and elephants. The sight of the tiger thrilled us,’’ said S Jayabharathi, a student of wildlife biology from the Govt Arts College, Ooty.

Forest officials of the Kalakad-Mundanthurai and Anamalais are not talking in terms of tiger numbers. “The core habitat is well protected and the tigers are safe,’’ said a forest officer in Anamalais. The 2008 Wildlife Institute of India (WII) estimates said there were six to eight tigers in each of these reserves adjoining Kerala. The number of tigers in TN was then estimated at 76. Says K Kalidasan of OSAI, a Coimbatore-based NGO, which coordinated the survey in the Anamalais tiger reserve, “Long-term conservation is not possible if the prey base is not increased.’’

Indirect evidence suggests movement of tigers in all the ranges of Coimbatore, say forest officers attached to the division. Tigers could have moved in from the adjoining Nilgiris biosphere, Silent Valley National Park and the upper reaches of Kerala forests abutting the division, the forest officers said.