Foreign tree species which made an entry into Indian forests more than a century ago, have become a serious threat to the movement of wildlife as well as the growth of native plants.

Forest officials say among the alien species, wattle was a major problem which would automatically get re-generated in several areas.

Until 2009, the Forest department systematically cleared these invasive tree species. But, in 2010, the Department recommended to the government that the wattle should not be removed. Due to this, the clearing of wattle in forest areas was stopped. Within the next two years, this invasive species has spread across several thousand hectares in the Western Ghats. Another problematical species is the eucalyptus.

The State government recently issued orders to clear wattle trees from various forest areas across the State. In Kodaikanal forest division alone the invasive wattle and eucalyptus have covered nearly 22,000 ha.

D. Venkatesh, District Forest Officer, Kodaikanal, said the invasive species will not allow any shrub or the local species of grass to grow around it. Additionally, they grow densely, leaving little space for the wildlife to pass through. Above all, a resin type of material will ooze from the tree during rainy days, which will turn the soil acidic.

As the invasive trees are not deep rooted, they get uprooted during windy days and fall on the road, creating problems for road users.

Mr. Venkatesh said that with the dense growth and absence of grass for feeding, the Indian gaur population from the wild had migrated to the town in search of fodder. “This is becoming a major problem in areas such as Kodaikanal town, Periyakulam, Thadiyankudisai, Thandikudi, Pannaikkadu and Kumbarayur.”

The Forest department had earmarked five hectare area each in seven Forest Ranges in the Kodaikanal Forest Division. They were stacking the dead and wind-fallen exotic tree species. So far 452.4 tonnes of dead and wind-fallen wood were removed and the Department had earned revenue of Rs. 2.29 lakh, he said.

A senior Forest official said the Department did not stop with mere clearance of the invasive species. They also planted Shola tree saplings in the cleared area. The Department cleared invasive tree species from 35 ha of area in Kodaikanal, Berijam, Mannavanur and Poombarai in Kodaikanal forest division. Similar effort is being taken in the Nilgiris South and North forest divisions, said a senior Forest official.

The Tamil Nadu Green Movement cautioned that less expensive, proper techniques, established and proven methods for clearing invasive tree species did not exist and the restoration of habitat required patience and long-term commitment. It was suggested that a scientific probe has to be done in an experimental plot and its outcome should be measured before starting a large-scale removal process.

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