Uprooting invasive trees to reclaim Erode’s tiger reserve

CHENNAI: Before the end of this year, wildlife in Sathyamangalam Tiger Reserve (STR) in Erode will have more space to move around freely as well as feast on a spread of native grass and shrubs. This is thanks to renewed efforts to clear the area of Senna spectabilis, an invasive species that has occupied more than 730 hectares of the wooded area. Clearing efforts began in January following a Madras high court order. “This invasive species was introduced as a plant of shade in coffee estates during the British regime,” says Devendra Kumar Meena, deputy director of STR.

“Slowly, the plant took over a large area of the reserve as well as the wooded area along the Thimbam-Karapallam Road. A majority of the tree species are found inside the reserved forest areas and affect the growth of native grass and other shrubs, which are important feed for herbivores such as deer, elephants and Indian gaur,” Meena said. There are 600 to 700 Senna spectabilis trees spread across a hectare of land in the STR. The medium density of this invasive species is about 400 trees per hectare. Following the HC order, the forest department had entered into an agreement with the Tamil Nadu Newsprint and Paper Limited (TNPL), which agreed to clear the species from the wooded areas within six months.

“However, the clearing will take more than six months to complete,” says Meena. A study by Kerala forest officials about the species showed that in 2013, Senna spectabilis had occupied a 14.6sqkm area in Wayanad Wildlife Sanctuary. A decade later, the same species spread over 123sqkm in the sanctuary. On an average, the TNPL is clearing three to four hectares on the invasive species. As the species can be used to make pulp, TNPL agreed to remove this invasive tree. For every tonne of tree cleared, TNPL will pay the STR `350, which will be used to restore the patches from where they have been cleared.

TNPL is allowed to knock down only trees that have a 5cm diametre, says the official. The clearing TNPL takes place under the direct supervision of a team of forest officials headed by a range officer. TNPL is removing the barks at the site and transporting only the logs. Clearing the invasive species from above the soil will not suffice as the seed deposits under the soil will germinate, says D Narasimhan, former associate professor of botany at Madras Christian College, Chennai. This tree belongs to the legume species, and the seeds ensconced in long pods, can get dispersed quickly. “First, the seed deposits need to be cleared,” he says. “Second, the clearing has to be taken up on a sustained basis for 3-5 years. Only then can it be controlled.”