With its snowy winters and dry summers, Kashmir’s climate differs from rest of the country. Once upon a time, however, it too had a warm monsoon climate. A new study reveals how rising mountains changed all that—shaping the region’s weather, landscape, and ecology.
Researchers from the Birbal Sahni Institute of Palaeosciences (an autonomous institution under the Ministry of Science and Technology), and the University of Kashmir analysed fossilised leaves from ancient lake bed sediments in South Kashmir. These sediments, known as the Karewas, hold vital clues to the Valley’s climatic history.
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For the uninitiated, the Karewas are thick deposits of clay, sand, silt and gravel found across the Kashmir Valley. Formed over millions of years, these layers were laid down in an ancient lake that once covered much of the region. Today, the Karewas are not only rich in fossils, but also crucial for agriculture, supporting crops like saffron and apples.
The study was conducted as part of the rich fossil leaf collection curated by the late Professor Birbal Sahni and Dr G.S. Puri, which is housed at the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow: collections recovered from the Karewa sediments.
These displayed remarkable diversity and preservation. Many of the specimens resembled subtropical taxa that no longer exist in the region’s current temperate climate.
A group of researchers from BSIP were intrigued by the striking mismatch between past and present vegetation, and this prompted their scientific investigation into the climatic and tectonic history of the Kashmir Valley using modern palaeobotanical methodologies.
By studying leaf fossils from the Lower Karewa formations, scientists reconstructed what the climate was like around 3–4 million years ago, during the late Pliocene period.
The study done by Harshita Bhatia, Reyaz Ahmad Dar and Gaurav Srivastava revealed that earlier, the average annual temperature was around 18°C, with warm winters and a long, 9–10 month growing season. The rainfall was heavy in summer, driven by monsoon winds, while winters were relatively dry. This high moisture levels and humidity suggested a lush, subtropical environment.
These conditions are radically different from today’s Mediterranean-type climate in Kashmir, where most rain comes in winter via the Western Disturbances.
The authors linked this dramatic shift to the tectonic uplift of the Pir Panjal Range, a sub-Himalayan Mountain range that gradually rose and blocked the Indian summer monsoon from reaching the valley. Around four million years ago, tectonic activity began pushing these mountains higher, eventually blocking the summer monsoon winds from entering the valley.
With its main source of rainfall cut off, Kashmir’s climate began transitioning into what we see today: cold winters, dry summers, and winter precipitation from the west. Over milennia, these rising mountains cut off the water supply, drying out the lush forests and transforming the region’s climate from subtropical to Mediterranean.
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Using CLAMP (Climate Leaf Analysis Multivariate Program), the scientists examined the shape, size and margins of fossil leaves to determine temperature and rainfall patterns, and cross-checked plant fossils with their modern relatives, using the help of the co-existence approach to estimate climate ranges. This helped them create a detailed snapshot of the Kashmir Valley’s ancient environment, rich with warmth and rain—until the mountains intervened.
The research offers a window into how landscapes and climates evolve in response to tectonic shifts. It also helps explain the region’s rich biodiversity, preserved in the fossil record of the Karewas.
The study, published in the journal 'Palaeogeography, Palaeoclimatology, Palaeoecology', highlights how geological processes like mountain-building can trigger major climate changes over time.
The lead author say that the findings could improve our understanding of past climate systems and how future environmental changes might unfold—especially in fragile mountain regions like the Himalayas.
