A new scientific study has traced how Assam’s Kaziranga National Park (KNP) evolved into the world’s most important refuge for the Indian one-horned rhinoceros, revealing a story shaped by climate change, shifting vegetation, human pressure and the decline of megaherbivores across the subcontinent.
Scientists from the Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute under the Department of Science and Technology (DST), have reconstructed the first long-term palaeoecological record from Kaziranga by analysing pollen and fungal spores preserved in sediment beneath the park’s wetlands. Their findings have been published in the international journal Catena (Elsevier).
The researchers extracted a sediment core measuring just over a metre from the Sohola swamp inside Kaziranga National Park. The layered mud acted as a natural archive, preserving microscopic pollen grains from plants and spores of dung-loving fungi, which together provided insights into past vegetation, climate conditions and herbivore activity over thousands of years.
According to the study, Kaziranga’s present-day landscape is markedly different from what it was in the past. Fossil evidence shows that megaherbivores, including the Indian one-horned rhinoceros, were once widely distributed across the Indian subcontinent. However, this range began shrinking during the Holocene period, with regional extinctions occurring in northwestern India.
The researchers attribute this decline to a combination of climatic changes -particularly during the late Holocene and the Little Ice Age – and increasing human activities such as habitat loss and overhunting. In contrast, northeastern India remained relatively climatically stable over the last 3,300 years and experienced comparatively lower human pressure. This stability enabled rhinoceroses to migrate eastward and eventually concentrate in the floodplains of the Brahmaputra, making Kaziranga their last major stronghold.
The study places Kaziranga within a broader global context of biodiversity loss. Worldwide, nearly 60 per cent of large herbivores are currently threatened, with Southeast Asia recording the highest number of at-risk species. Northeast India, part of the Indo-Burma biodiversity hotspot, continues to host several endangered species but also faces growing pressures from urbanisation, industrialisation, deforestation and natural hazards such as floods and earthquakes.
By documenting how long-term climate and vegetation changes influenced wildlife survival, migration and extinction, the researchers say the findings offer valuable lessons for present-day conservation. The study underscores the importance of understanding deep ecological history to guide effective wildlife management and conservation strategies in the face of ongoing and future climate change.
Kaziranga National Park, a UNESCO World Heritage Site, today remains a symbol of successful conservation, protecting the largest population of the Indian one-horned rhinoceros – and, as the study suggests, the last great home shaped by millennia of environmental change.
