A recent study has revealed that Senna spectabilis (calceolaria shower), an invasive plant species known for its rampant growth, has spread to more wildlife habitats of the Nilgiri Biosphere Reserve (NBR), including the Wayanad Wildlife Sanctuary (WWS).
The study, jointly conducted by Ferns, a nature conservation society based in Wayanad, and the Forest department, revealed that the wild growth of the plant and its copious nature posed a serious threat to wildlife and indigenous plants in the NBR.
Twelve years ago when the species was identified as a threat, the plants were sparse in Wayanad. The distribution of the species was restricted to 14.6 sq km of the sanctuary in 2013 and it spread to 78.9 sq km in 2019. However, the current study shows that the species has spread to 123 sq km, says Ferns president P.A. Vinayan, who led the study.
Senna spectabilis flower
“In the past 10 years, the sanctuary has become impenetrably dense with the invasive species. If urgent action is not taken, it may cover the entire WWS in the next 10 years. Besides, human-animal conflict will increase significantly owing to Senna invasion,” Mr. Vinayan adds.
Spread in south India
The degree of invasion is quite high in the Tholpetty and Muthanga ranges of the WWS. The study says almost 30 lakh Senna trees (with more than 10-cm girth) have been found in the sanctuary. An adult tree produces an average of 238.9 seed pods with each pod consisting of 103.3 seeds, which means the 30 lakh trees produce an average of 70.48 billion seeds a year.
The species is spreading at almost the same rate in the nearby Bandipur, Nagarhole, Mudumalai and Sathyamangalam tiger reserves. Its spread in south India is not restricted to the NBR but pockets of the Western Ghats, including the Bilgiri-Rangan hills, Malai-Mahadeswara hills, Bhadra Tiger Reserve in Karnataka, Periyar Tiger Reserve, Attappady region of Palakkad district in Kerala, Meghamalai Tiger Reserve, and Coimbatore forest division in Tamil Nadu, he says.
The Forest department has been granted ₹46 crore to uproot the plants, which includes ₹40 crore under the Rebuild Kerala Development Programme and ₹6 crore from NABARD, P. Muhammed Shabab, Conservator of Forest (Wildlife), Palakkad, told The Hindu. “We are planning to launch the uprooting project in a week. The department is planning to girdle trees above 10 cm girth, while others will be uprooted,” he adds.
