Invasive weeds killing ecology

Chennai: At least half a dozen districts in the state are suffering ecological disaster due to weed infestation. The situation is serious in Ramanathapuram, the Nilgiris, Vellore, Dharmapuri, Tiruchy and Coimbatore districts, said wildlife biologist A. Kumaraguru of Biodiversity Conservation Foundation. 

 

Invasive tree species  absorb surface stormwater. Their strong dispersal of seeds has also adversely eliminated Shola trees endemic to Tamil Nadu forests and this will lead to reduced rainfall.  The situation is even worse along Cauvery river banks. Invasive species like Ipomea and water hyacinth have removed native species. This means there is no filter in preventing the agricultural contaminants entering the river, Kumaraguru said.

 

Sensing trouble in ecology, Vellore Institute of Technology has now cleared the Juliflora (Vellikathaan) along the Palar river basin for five kilometers. “VIT has been periodically engaging environmentalists to study the ecological changes in Vellore and suitable recommendations are followed. Last year, the nearby hills were adopted in coordination with the state forest department. Indigenous tree saplings are planted. To ensure that they survive in arid condition, watering is done through drip irrigation,” said G.V. Selvam, vice president, VIT. 

 

Removal of Juliflora has been completed for five kilometres and there are plans to clear the entire Palar stretch from invasive species and debris so that the run off water during monsoon percolates along the Palar river basin benefiting Vellore, he added.

 

Removal of invasive species is a long pending issue. Water hyacinth is another bigger threat affecting the quality of lakes and water bodies in TN. There is a need for removal of all foreign plants, so that ecological benefits like rainfall, vegetation and soil fertility can be enhanced, explained D. Narasimhan, Professor of botany, Centre for Floristic Research, Department of plant biology, Madras Christian College.

 

“Most of the invasive species started spreading during early colonial period and they started spreading during 1980s and 1990s when the forests were cleared for development,” said Mr K. V. R. K. Thirunaranan, founder, the Nature Trust. For instance, invasive plant Parthenium hysterophorus is a major menace in Hosur, Dharmapuri and Palani areas. Most of the invasive species were introduced during colonial period and no major effort was made to de-weed them for several decades, added Thirunaranan.

 

Farmers in the state are suffering due to weed infestation as surface water is absorbed exorbitantly by invasive plant species which dominate arid districts such as Thoothukudi, Ramanathapuram and Dharmapuri, former minister and Tiruvadanai MLA Suba Thangavelan told the State Assembly on Wednesday.

 

He sought immediate action against Prosopsis Juiflora (Velikathaan in Tamil). It absorbs moisture in the atmosphere adding to the arid condition. Farmers are unable to return to irrigation because of weeds, he said.

 

With monsoon being a failure, the situation in Ramanathpuram is becoming bad to worse as invasive species make these regions more arid. He also alleged that 14 lakh coconut trees in western and arid districts of Tamil Nadu withered due to pest attack.

 

Responding, agriculture and housing minister C. Vaithilingam said the issue would be studied and taken up with the Chief Minister for necessary action. A senior forest department official said that through the Tamil Nadu Biodiversity Conservation and Greening Project, for the past three years invasive species are being removed periodically. Several hectares of invasive species like Lantana camara and Polithenium have been cleared in Kodaikanal, Anamalai and The Nilgiris wildlife divisions, but in the case of revenue and poromboke lands, the forest department cannot clear the weeds as the land belongs to other government departments, the official said.

 

“Not only Juliflora, there are at least a dozen invasive species threatening the biodiversity of Tamil Nadu and these plants also have the capacity to reduce the water catchment of river banks”, said forest department biologist G. Kamaraj. 

 

All the invasive species are certainly a threat to ground water table on a long term basis. For instance, Ipomea grows along the Cauvery River depleting the surface water. 

 

Similarly, Eucalyptus and Wattle trees have been a disaster to the ecology of Kodaikanal and Nilgiris hill stations draining ground water, he explained. Initially, these species were considered a boon to farmers as they provided livelihood, when agriculture failed. But now its time to weed them out so that the ecology can be restored as an effective anti-drought mechanism, Kamaraj added.