Exotic weeds a threat to ecology

Invasive species bring down food base of herbivores

June 12, 2015 12:00 am | Updated 05:43 am IST - COIMBATORE:

Spotted deer looking for food at the MTR.— Photo: M. Sathyamoorthy

Spotted deer looking for food at the MTR.— Photo: M. Sathyamoorthy

For four years, the Forest Department has been removing the exotic weeds and invasive species proliferating in the forests of The Nilgiris biosphere, but lack of manpower and financial resources is pegging back the effort.

The invasive species such as lantana camera, eupatorium and parthenium hysterophorus affect vegetation in terms of native species and thereby bring down the food base of the herbivores.

Any setback to the herbivore population owing to non-availability of fodder will, in the long run, have a proportionate effect on the carnivore population as well, say forest officials.

 The Mudumalai Tiger Reserve, spread over 321 sq km, has a high density of tiger and leopards. The North and South Divisions, covering 1,100 sq km, also have a good population of carnivores.

It has become a common sight to see flocks of sambar deer and spotted deer and even huge mammals like the Indian Gaur and elephants wading through largely grown exotic species, activists say.

 According to a senior forest official in the MTR, the park management began removing the invasive species four years ago at the rate of 500 hectares every year and the site was maintained for three years to prevent resurfacing.

As such this requires enormous manpower and a huge financial allocation , he points out.

 At this rate, environmentalists say, the clearing of invasive species will take a long time.

“Until then, the effect on native vegetation and the resultant impact on herbivores and carnivores will continue,” says V. Ramsundar, an official involved in the study of the impact of weeds and invasive species.

Use of machinery

 Deployment of machines for removing weeds did not go down well with environmentalists and forest managers as earth movers also caused damage to native vegetation. Considering the sensitive ecology and presence of micro bio-diversity, forest managers are averse to the use of machinery.

They are also apprehensive of using chemicals for eradicating invasive species.

 K. Kalidasan of Osai says that institutions such as the Tamil Nadu Agriculture University (TNAU)  and the Institute of Forest Genetics and Tree Breeding (IGTB) could be roped in to study the commercial value of these weeds and species. 

Based on the commercial value, agencies could be permitted to remove them in a controlled and regulated atmosphere.

Similarly, there could be research on the use of these weeds as bio-fuel so that the removal of weeds and their exploitation could be entrusted to agencies that could make money and contribute to the wellbeing of forest ecology, he adds.

On the use of herbicide and biological control, there is need to have them studied on model plots in smaller pockets before introducing them to ecologically sensitive forests rich in micro bio-diversity.

“These options need to be tried as manual removal of weeds is not only time consuming but also expensive,” he points out. 

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