Manas Tiger Reserve loses 44% grassland to invasive species – Implications for rhinos and biodiversity

Overview Over the past three decades, the Manas Tiger Reserve has seen a sharp decline in its grassland cover. In 1990, grasslands occupied 53.61% of the reserve; by 2019 they fell to 30.24%, a loss of 43.59% (23.37% absolute area). The decline threatens species that depend on open habitats, such as the Indian rhinoceros , pygmy hog, and hispid hare. Key Developments Fourteen invasive alien plant species, including Chromolaena odorata and Lantana camara , have spread, converting grasslands into woodlands. Large herbivore numbers fell due to poaching and civil unrest (1988‑2004), reducing natural grazing pressure. Uncontrolled forest fires and indiscriminate livestock grazing further degraded habitats. Woodland area rose from 40.42% (1990) to 60.62% (2019), accelerating succession. Encroachment of 3,709 hectares in core zones has been recorded since the 1980s. Important Facts Reserve area: 2,837.31 sq. km ; core tiger habitat: 526.22 sq. km . Grassland loss: 43.59% relative, 23.37% absolute . Invasive species list: Chromolaena odorata, Mikania micrantha, Lantana camara, Leea asiatica, Bombax ceiba, Dillenia pentagyna . Manas shares a border with Bhutan’s Royal Manas National Park (1,057 sq. km, elevation 80‑2,707 m). Management authority: BTC Forest Department. UNESCO status: UNESCO World Heritage Site since 1985. UPSC Relevance The case illustrates several themes in the UPSC syllabus: (i) environmental governance – role of state agencies and community bodies in managing protected areas (GS3); (ii) invasive species management – ecological impact of non‑native flora on biodiversity (GS3); (iii) human‑wildlife conflict and the effect of civil unrest on conservation (GS3); (iv) policy implementation challenges in remote, conflict‑prone regions (GS2). Understanding these links helps answer questions on biodiversity loss, forest policy, and inter‑state cooperation. Way Forward Strengthen early‑detection and rapid‑response mechanisms for invasive species under the Invasive Species (Regulation) Act . Restore grazing pressure by re‑introducing native herbivores and managing livestock access. Implement community‑based monitoring involving local tribes and NGOs to curb encroachment. Integrate fire‑management plans with climate‑adaptation strategies. Enhance trans‑boundary cooperation with Bhutan for coordinated habitat management.