By Ritambhara
Birbal Sahni read fossil plants as records of India’s past climate and terrain. A botanist trained at Lahore and Cambridge, he spent three decades using stone leaves and petrified stems to show how continents and mountains had moved. In 1936 he became the first Indian botanist elected a Fellow of the Royal Society.
Sahni was born on 14 November 1891 at Bhera, in Punjab, now in Pakistan. He studied under the palaeobotanist Albert Seward at Cambridge, and in 1920 the two published a revision of the fossil plants of India’s Gondwana rocks. In 1946 he founded the institute of palaeobotany in Lucknow that now carries his name. He died there on 10 April 1949, a week after the foundation stone of its new building was laid.
A lost plant from the Rajmahal Hills
His best-known find came from silica-rich cherts near the village of Nipania in the Rajmahal Hills, in present-day Jharkhand. Earlier workers had described seeds, wood and leaves from these beds as separate fossils. Sahni showed that they belonged to one plant. In a 1948 paper in the Botanical Gazette he named the group the Pentoxyleae, after the five strands of wood in its stem. This Jurassic seed plant has no close living relative, and botanists still debate its place. The paper was his last published work. In 1936 he also used the spread of fossil floras to support Wegener’s theory of continental drift.
Leaves that measure a mountain
In Kashmir he applied the same method to younger rocks. The Karewas are thick beds of clay, sand and gravel laid down in an ancient lake on the valley floor. In a 1936 paper Sahni reasoned that each fossil plant records the altitude at which its living relatives grow. Where such fossils lie far above that height, the ground itself must have risen. In 1945 G S Puri, whose paper Sahni communicated, reported a lotus leaf fragment in Karewa beds at about 9,000 feet in the Pir Panjal. Puri read this water plant as evidence that Himalayan mountain-building had lifted the lake beds.
The leaves tested again in 2025
In 2025 researchers from the Birbal Sahni Institute and the University of Kashmir returned to Karewa leaves, using a collection curated by Sahni and Puri. They estimated past temperature and rainfall from leaf shape, size and margins. About four million years ago the valley carried warm, humid subtropical forest. The authors linked its later drying to the rise of the Pir Panjal, which came to block the summer monsoon. The study, in Palaeogeography, Palaeoclimatology, Palaeoecology, applied the reasoning Sahni set out in 1936.
The Gondwana rocks Sahni catalogued in 1920 also hold India’s coal. The Indian Bureau of Mines places over 99 per cent of the country’s coal reserves in Gondwana sediments (2017). The Ministry of Coal reported output of 1,047.57 million tonnes in 2024-25, the first year above one billion tonnes (Ministry of Coal, 2025).
Sahni showed that buried plants carry a measurable record of the climate they grew in. India now mines the remains of Gondwana vegetation at over a billion tonnes a year. His work asks readers to see that coal as stored climate history, and to weigh what burning it adds to the next record.
