14 invasive plants behind grassland loss in one of India’s first tiger reserves
GUWAHATI Over 30 years, 14 invasive plant species have been a major factor behind one of India’s first tiger reserves losing more than 43% of
GUWAHATI Over 30 years, 14 invasive plant species have been a major factor behind one of India’s first tiger reserves losing more than 43% of its grassland cover, crucial for the survival of the Indian rhinoceros and other rare animals, including the pygmy hog and the hispid hare. Data provided by the Forest Department in Assam’s Bodoland Territorial Council (BTC) have revealed that the grassland cover in the 2,837.31 sq. km Manas Tiger Reserve declined from 53.61% in 1990 to 30.24% in 2019. The relative loss and absolute reduction in grassland area work out to 43.59% and 23.37%, respectively. The tiger reserve is contiguous with the 1,057 sq km Royal Manas Park in Bhutan, which ranges in elevation from 80 m above sea level to 2,707 m.
Officials attributed the degradation and shrinkage of grasslands in Manas to a “combination of ecological and anthropogenic factors”. These included a prolonged period of civil unrest and extremism between 1988 and 2004, during which regular habitat management activities were severely disrupted, uncontrolled forest fires, and indiscriminate livestock grazing. A factor was the decline of large herbivores, thereby reducing grazing and browsing pressure essential for maintaining grassland ecosystems. Poaching, allegedly by extremist groups that traded animal body parts for firearms, wiped out the park’s rhino population by the early 2000s, necessitating an exercise to repopulate with rhinos from Kaziranga and other wildlife habitats in Assam. Although Manas has more trees than it did more than three decades ago, it has traditionally been home to grassland-linked species.
However, the invasive alien plant species, avoided by the herbivores, have constricted the native plant species that the animals are dependent on. These include shrubs such as Chromolaena odorata, Mikania micrantha, Lantana camara, and Leea asiatica, and aggressive woody species such as Bombax ceiba and Dillenia pentagyna. “The woody invasive species have accelerated the succession of grasslands into woodlands,” a BTC Forest official said. The woodland area of Manas, a UNESCO World Heritage Site with a core tiger habitat of 526.22 sq. km, increased from 40.42% in 1990 to 60.62% in 2019. “The substantial loss of grassland habitat has adversely affected the ecological integrity of the park and reduced the availability of suitable habitat for several mega-herbivores, including the Indian rhinoceros, pygmy hog, hispid hare, eastern swamp deer, Asian elephant, wild water buffalo, gaur, and hog deer,” a statement read.
The BriefWire