Nilgiri reserve worst hit by killer plants: Study

CHENNAI: Even as the death of 10 tigers, including six cubs, in Nilgiri Biosphere Reserve raised concerns about the availability of adequate prey, a study by the Wildlife Institute of India (WII) and National Tiger Conservation Authority (NTCA) alarmed that the biosphere reserve is one of the largest hotspot areas for invasion of alien invasive species.

As per the report, Nilgiri Biosphere Reserve has been predominantly invaded by Lantana camara, Prosopis juliflora and Chromolaena odorata. Meanwhile, Southern Eastern Ghats, which run across the northern district of Tamil Nadu, are amongst the most densely invaded landscapes predominately by Prosopis juliflora and Lantana camara.

The study revealed that a total of 750,905 sqkm of natural areas in the country – 66% of natural areas – were found suitable for invasion by high-concern invasive plants.

The remaining 35% of relatively uninvaded areas are largely contiguous systems with the least human modifications owing to extreme climate (Thar desert) or terrain (Northeast hills).

“Another study showed that wet ecosystems displayed biotic resistance to invasive plants, which was particularly observed in protected areas and lost in multi-use areas,” it said.

The study also pointed out that the survival of tigers depends on high densities of herbivores, which requires large wilderness areas with abundant nutritional forage.

Plant invasions can likely reduce native forage plants and habitat quality, thereby endangering the dependent trophic structure.

An assessment by the TN government in 2020 said more than 3.18 lakh hectares of forest land in the State are invaded by the seven most common invasive alien species.

Also, 262 sqkm (69% of total area) of montane grasslands in the Palani Hills and 180 sqkm (58%) of montane grasslands in the Nilgiri have been lost due to exotic tree invasion and agricultural expansion.