A groundbreaking fossil discovery in Assam’s Makum coalfields has revealed that two tree species now endemic to the Western Ghats — Nothopegia travancorica and Nothopegia castaneifolia — were once widespread across northern and northeastern India, offering striking evidence of ancient climatic shifts and their impact on biodiversity.
Scientists from the Birbal Sahni Institute of Palaeosciences unearthed fossilised leaves of their extinct relatives, Nothopegia oligotravancorica and Nothopegia oligocastaneifolia, dating back 24 million years to the Oligocene epoch. The study indicates these species gradually migrated southward as Himalayan uplift led to cooler temperatures in the north, forcing warm-climate flora to seek refuge in stable tropical environments like the Western Ghats.
“These species were once distributed from Assam to Darjeeling but moved south due to falling winter temperatures,” explained lead researcher Gaurav Srivastava, noting that the Himalayas rose sharply about 11 million years ago.
The researchers highlighted venation patterns in the fossilised and modern leaves to establish evolutionary links. Today, Nothopegia travancorica is a small understorey tree, five to eight metres tall, restricted to specific humid forest pockets in the Western Ghats — including Ratnagiri, Panaji, Palakkad, and Thiruvananthapuram.
Forest ecologist B.R. Ramesh, co-author of Atlas of Endemics of the Western Ghats, notes that this is not an isolated case:
“Several species, such as those from the Dipterocarpaceae family, were once widespread across central and northern India. Now, their living members are found only in humid zones like the Western Ghats and northeast India.”
This fossil evidence underscores the vital role of warm-climate refuges in preserving biodiversity amid global climate fluctuations. As warming accelerates, researchers warn that many existing taxa could face the same fate — local extinction or severe habitat restriction — unless decisive action is taken.
