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Manas Reserve Loses Over 43% Grassland to Invasive Plants
11 Jul
Summary
- Manas reserve lost 43.59% grassland cover between 1990 and 2019.
- Invasive plant species have overtaken native flora essential for herbivores.
- Woodland area expanded significantly, impacting wildlife habitats.

Manas Tiger Reserve has seen its grassland cover plummet by 43.59% over three decades, declining from 53.61% in 1990 to 30.24% by 2019. This significant loss of vital habitat is largely attributed to the proliferation of 14 invasive plant species that outcompete native flora.
The invasive species, such as Chromolaena odorata and Mikania micrantha, are avoided by herbivores. Their aggressive growth has transformed grassland ecosystems into woodlands, with the woodland area increasing from 40.42% to 60.62% during the same period.
This ecological shift has critically impacted mega-herbivores, including the Indian rhinoceros, pygmy hog, and hispid hare, which depend on the grassland ecosystem. The degradation is a result of combined factors including prolonged civil unrest until 2004, forest fires, and unchecked livestock grazing.
The reserve, a UNESCO World Heritage Site, also faces challenges from encroachment, with 3,709 hectares of its core area encroached upon since the 1980s. The decline in grassland habitat has had cascading negative effects on carnivores like tigers and leopards.