Guwahati: Officials at Assam’s Manas National Park and Tiger Reserve have reported a nearly 50% decline in grassland cover over the past three decades, raising alarm over the future of the park’s delicate ecosystem.
Field Director C. Ramesh explained that while the natural transition from grassland to woodland typically takes over a century, this process has accelerated dramatically within the UNESCO World Heritage Site.
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He attributed the rapid shift to a mix of natural and human-driven causes, including climate change. As a result, herbivores have begun clustering in the few remaining grassy areas.
“We’re observing a fast decline in grasslands, while woodland areas are expanding. Though this is part of ecological succession, the pace concerns us because grasslands are vital to maintaining balance in this ecosystem,” Ramesh stated.
According to park records, grassland cover has shrunk by an estimated 50 to 60 percent over the last 30 to 35 years. Ramesh clarified that native trees and shrubs have gradually replaced the grasses. As a consequence, animals such as deer, who are non-territorial and roam in search of food, now concentrate around the remaining grassland pockets.
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Manas National Park is globally unique for being the only habitat where species such as the greater one-horned rhinoceros, swamp deer, hog deer, pygmy hog, hispid hare, wild buffalo, Bengal florican, tiger, and Asian elephant co-exist. The rapid degradation of grasslands could jeopardize the survival of these species.
Experts Raise Concerns Over Multiple Threats
Grassland expert and conservationist Dr. Bibhuti Prasad Lahkar highlighted both natural and human-driven threats to the ecosystem. He explained that biotic processes like succession and the spread of invasive plant species gradually transform grasslands into scrublands and eventually woodlands. Climate change, he added, accelerates this progression.
“Anthropogenic pressures, such as excessive grazing, unmanaged burning, and over-harvesting of grasses, further compound the issue,” Lahkar noted.
He warned that the loss of grass variety also threatens species-specific feeders. “Different animals rely on specific grass species. If those grasses disappear, the animals depending on them will vanish too,” he said.
Lahkar pointed out that periodic flooding plays a crucial role in rejuvenating sub-Himalayan grasslands.
However, areas like Manas rarely experience sustained flooding, and when it does occur, it often lasts just a few hours. Additionally, erratic rainfall and changes in soil dynamics have altered the composition and productivity of the grasslands.
Climate Change and Invasive Species Add Pressure
Echoing Lahkar’s concerns, Dr. Minakshi Bora, an environmental science professor at Gauhati University, stated that climate change has disrupted the park’s ecological balance. She pointed to invasive species like Chromolaena odorata and Mikania micrantha as key threats that outcompete native grasses, leading to reduced biodiversity and altered ecosystem functioning.
Bora also cited recent studies showing that higher temperatures and falling rainfall levels have impacted the hydrological cycle in the Manas River Basin. This has led to lower water flow during summer, more frequent droughts, and deteriorating water quality, all of which directly stress the grassland ecosystem, which she called the “backbone” of the park.
She added that flash floods, exacerbated by melting Himalayan glaciers and heavy sedimentation, have caused widespread damage to vegetation and increased wildlife casualties.
Restoration Plan Underway Despite Gaps in Climate Data
Despite these challenges, officials acknowledge a gap in data. Ramesh admitted that the forest department lacks a weather station within the park and has not yet conducted a focused study on the effects of climate change within its boundaries. This absence of localized climate data makes it difficult to track long-term changes in temperature and rainfall.
To address the crisis, the park authorities, in partnership with several NGOs, have drafted a 10-year Grassland Management Action Plan (GMAP). This comprehensive effort aims to restore and conserve grasslands, improve wildlife habitats, and strengthen the overall ecosystem resilience of Manas National Park.