From 640 BC to the present, Kaziranga has become more open, with expanded grasslands and less dense forests. File. | Photo credit: RITU RAJ KONWAR
A new scientific study of swampy soil has revealed how the vegetation of Assam’s Kaziranga National Park has evolved over 3,000 years to become a prime habitat for India’s one-horned rhinoceros.
The study, published in the Dutch Catena, an interdisciplinary journal of soil and geomorphology, also highlights the shift of large herbivores from the northern and western parts of the Indian subcontinent to the northeastern region.
The author of the study is 430 m2 Kzirang National Park is Sidhan K. Basamarary, Swai Tripapathi of Birknhi. ; H. This is Gangtok.
The researchers collected 110 cm deep sedimentary soil from the northwest side of Kaziranga’s Sohola swamp at 5 cm intervals for palynological analysis and radiocarbon dating. The layer containing plant pollen grains and microscopic fungal spores combined with animal droppings acts like a natural history book.
By studying these tiny remains and dating them, scientists have reconstructed how vegetation, climate and the movement of large animals changed over time.
Pictorial development showing a. Dense forest with wider and swampy conditions with low game activity (3290 years -1700 years), b. Relatively less dense and less deep water with increased wildlife activity (1700 years-640 years), c. Relatively less dense forest and less deep swamps with increased wildlife activity in KNP (640 years-present). Photo: Special arrangement
“Kaziranga looked very different 3,290 to 1,700 years before present (BP). The park during this phase of warm and humid climatic conditions had a tropical dense mixed forest dominated by Bombax, Cinnamomum, Duabanga and Lagerstroemia trees with less grassland,” Dr Basumatary told The Hindu. BP is a time scale where the “present” is set to 1950. Fungal spores were found in small amounts, indicating fewer grazing animals during this phase.
Expansion of pastures
The soil study further showed that the vegetative cover began to change between 1700 and 640 years BP. Evergreen forests slowly declined and deciduous trees and grasses began to occupy the space.
“This shift indicated slightly drier conditions and a more open landscape. Around this time, spores of dung-associated fungi increased, indicating that large plant-eating animals were becoming more common,” Dr Basumatary said.
This period also saw the first appearance of mimosa, an invasive plant species. Its arrival indicated an early ecological disturbance, possibly associated with climatic stress or increasing human activity in nearby areas. “The Mimosa invasion needs proper management,” said Dr. Gogoi.
From 640 BC to the present, Kaziranga has become more open, with expanded grasslands and less dense forests. Dr Tripathi said there was a strong impact of the Little Ice Age in the northern region of India, which eventually affected wildlife habitats.
“During this period, we found a spike in fungal spores, suggesting an increase in the number of mega-herbivores such as rhinos, elephants, buffalo and deer,” she said.
While the sedimentary profile of Kaziranga revealed an absence of agricultural activities, scientists hypothesized that rhinos migrated to the park from the western and northern parts of the Indian subcontinent as a result of climate change and increasing human pressure.
The hypothesis was based on a comparative analysis of vegetation dynamics and climate variables with previously recorded rhinoceros bone fossils and historical records.
Kaziranga is home to more than 70% of the world’s total population of about 3,700 one-horned rhinos, making it the most critical habitat for the species.
Published – 01 Jan 2026 04:02 IST
