Guwahati: A new study by the Dehradun-based Wildlife Institute of India (WII) has revealed that the iconic grasslands of Kaziranga Tiger Reserve in Assam— vital for species like rhinos, elephants, and swamp deer — have shrunk by 318.3 sq km between 1913 and 2023.
To put this in perspective, the loss is almost equivalent to the area of Kolkata city or about half the size of Mumbai, according to WII researcher Umar Saeed.
The researchers analyzed historical topographic maps, satellite imagery spanning 110 years, and climate data from 1980 to 2022 to study land-use and climate dynamics in the Brahmaputra floodplain.
Their findings show that while grasslands have steadily declined, forest cover has expanded dramatically — from just 0.6 sq km in 1913 to 229.2 sq km in 2023.
Waterbodies, which had initially expanded until 2013, have started shrinking in the past decade, reflecting changes in river morphology and hydrology.
Climatic trends over the century indicate subtle shifts: maximum temperatures have slightly dipped from 37.5°C to 36°C, while minimum temperatures have risen from 6°C to 8°C, resulting in warmer nights. Relative humidity and rainfall have increased, improving soil moisture levels.
The study, titled ‘A Century of Land Use and Climate Dynamics Transformation at Kaziranga Tiger Reserve’, was presented at WII’s 18th Internal Annual Research Seminar.
Scientists highlighted that both human activities and climate changes are driving these ecological transformations in the UNESCO world heritage site.
While forest expansion may seem positive, the loss of open grasslands poses serious challenges for Kaziranga’s herbivore populations.
“Grasslands sustain megaherbivores and cervid species. Rhinos, swamp deer, hog deer, and sambar require extensive grasslands for foraging and survival,” explained Saeed, adding that Kaziranga is also home to the last remaining original populations of wild water buffalo (Bubalus arnee).
The researchers further noted that invasive plant species, including Mikania micrantha and Chromolaena odorata, are encroaching on grasslands, impacting the feeding and behavior of key herbivores.
“Megaherbivores play a crucial role in the food web of Kaziranga. Continued grassland depletion could significantly affect their populations in the long term,” said Saeed and fellow researcher Rashmi Das, whose study spanned 2019 to 2024.
The WII scientists stressed the urgent need for adaptive management strategies that focus on habitat regeneration, maintaining hydrological balance, and building climate resilience to protect this sensitive floodplain ecosystem.