Senna spectabilis, an exotic fast‑growing tree, now covers over 40% of Karnataka’s Nagarahole National Park, threatening native vegetation and wildlife in the Western Ghats. The forest department, together with the Indian Institute of Wood Science and Technology, is drafting a protocol for eradication, warning that unchecked spread could alter the region’s ecology unless removal and habitat‑restoration measures are implemented.
The invasion marks another phase in the region’s long battle against invasive plants such as Parthenium, Eupatorium and Lantana, and is deemed especially hard to manage because the species grows rapidly and remains green even during the dry summer months.
Originating from Kerala, Senna spectabilis has spread into Karnataka and now dominates large stretches of Nagarahole and Bandipur National Parks as well as adjoining forests in Tamil Nadu and Kerala. In Nagarahole, which spans about 842 sq km, dense growth of the tree suppresses native grasses and other vegetation, hindering natural regeneration.
Experts are particularly worried about the impact on grasslands and bamboo habitats, both crucial to the forest ecosystem, and note that herbivores generally do not feed on its leaves, further limiting its ecological value as a food source.
Principal Chief Conservator of Forests (Wildlife) Kumar Pushkar said, “The rapid proliferation of Senna spectabilis in Nagarahole and Bandipur has become a critical ecological threat comparable to the earlier spread of Lantana camara.” He added that scientific intervention is essential because improper removal could trigger even denser regrowth.
Pushkar explained that the central challenge lies in the species’ high coppicing ability and resilient root system, stating that simply cutting the trees down results in vigorous regeneration from the remaining roots. Trials near Murkal in Nagarahole showed that cut patches regenerated more densely, leading him to stress that complete removal of the root system is essential for effective eradication.
The tree spreads rapidly through seeds dispersed by wind and water and can also regenerate from its roots. Consequently, experts recommend continuous monitoring and repeated clearing operations for at least five years after removal.
Forest authorities and NGOs have already undertaken small‑scale removal and habitat‑restoration efforts at DB Kuppe, Antharasanthe, Nagarahole, Veeranahosahalli and Hunagund.
Karnataka is also exploring the Tamil Nadu model of supplying harvested Senna wood to paper mills, with West Coast Paper Mills expressing interest.
A Wayanad‑based NGO has been assigned a trial plot in Nagarahole for manual uprooting of the species, although officials describe the method as highly labour‑intensive.