Invasive species threatens wildlife

(Mains GS 3 : Conservation, Environmental Pollution and Degradation, Environmental Impact Assessment.)

Context:

• A recent study, organised by Ferns, a nature conservation society, in association with the Kerala Forest Department, revealed that the invasive species has now spread through the most iconic wildlife habitats of the Western Ghats, destroying habitats of elephants, deer, gaur and tigers by pushing out native flora.

Serious concern:

• The absence of a comprehensive strategy to arrest the wild growth of invasive alien plants in the forest areas of the Nilgiri Biosphere Reserve, including the Wayanad Wildlife Sanctuary (WWS), poses a threat to wildlife habitat.
• Apart from the spread of Manjakkonna ( Senna spectabilis ) and exotic plants such as Elappullichedi ( Hypoestes phyllostachya ) and Kudamaram or Umbrella Tree ( Maesopsis eminii ), Dhritharaashtra pacha (Mikenia micrantha ), Arippoo/konginippoo ( Lantana ) and Communist pacha ( Eupatorium ) are also posing a serious threat to the region.

Allelopathic traits:

• Senna spectabilis is more dangerous than other exotic species owing to its quick growth.
• The allelopathic traits of the species prevent other plants from growing under it.
• It is a form of chemical warfare where the shed leaves decompose and change the chemical composition of the soil, rendering it unsuitable for the growth of other plant species.
• This drastically affects primary productivity at the ground level as the forest floor is almost bare under the invasive species and grasses and herbs get completely wiped out and herbivores are deprived of their forage.
• Further, the carrying capacity of forests to feed wildlife is drastically declining under the invasion, which accelerates man-animal conflict further.

Planted as avenue trees:

• The invasive species found its way to Wayanad in the 1980s, when the seedlings of the plant were first raised in the nurseries of the social forestry wing, and planted as avenue trees.
• Nearly 3,000 sq km of the region, including three forest divisions in Wayanad contiguous with the Nagarhole National Park and the Bandipur Tiger Reserve in Karnataka and the Mudumalai Tiger Reserve in Tamil Nadu, has wild growth of the invasive plant.
• Taking clues from the studies conducted in various parts of the world and based on the recommendations from research institutions like Kerala Forest Research Institute (KFRI), the sanctuary management has been trying out several control measures to eradicate the plant, but without the desired result.

Threat to native biodiversity:

• The Forest Departments of Karnataka and Kerala realised that the tree is a threat to native biodiversity nearly 10 years ago and initiated actions to contain its spread.
• The study found around 23% of the area of Wayanad Wildlife Sanctuary is infested by Senna spectabilis.
• The study says 1,305 trees were found in one hectare in the most affected areas of the sanctuary and  the species are spreading at almost the same rate in the adjacent Tiger Reserves.

Failed eradication:

• The Kerala Forest Department attempted to remove the trees by uprooting, girdling, cutting, chopping the tree branches, and even testing the application of chemicals.
• However, all the efforts were in vain and instead, multiple coppice shoots started growing from each cut tree stump.
• The situation is similar in Karnataka and Tamil Nadu as senna eradication is a major component of the forest management plan but it’s yet to make any remarkable change in the forest.

Conclusion:

• The quick spread of the invasive plants leads to food shortage for wildlife populations, especially herbivores and would worsen the human-animal conflict in the region. 
• Thus, a long-term joint drive by the authorities of the adjoining Tiger Reserves is the only possible solution to eliminate the threat.