Deodhar trees don’t just chronicle climate; they bear the scars of survival. By examining tilted stems and impact marks, the researchers mapped 168 years of rockfall activity from 1853 to 2021, identifying 53 events, including eight high-intensity barrages.

In the shadow of snow-capped peaks, where the Baspa River carves through the rugged Kinnaur valleys of Himachal Pradesh, a quiet catastrophe unfolded in July 2021: massive boulders tumbled from unstable slopes near the village of Batseri, threatening homes, farmlands, and the fragile lifeline of the remote Himalayan community.

As the dust settled and villagers assessed the damage, scientists from India’s Birbal Sahni Institute of Palaeosciences (BSIP) saw not just destruction, but a call to decode the mountains’ hidden history. Turning to the stoic Deodhar trees – Cedrus deodara – that have silently witnessed centuries of change, they unearthed a 463-year chronicle of drought, deluge, and disaster.

This tale, pieced from tree rings etched like ancient scrolls, reveals how climate change is turning the western Himalayas into a tinderbox of geohazards, with implications rippling from local slopes to national resilience.

The study, published in the journal Catena and spotlighted by the Department of Science and Technology (DST) on December 10, 2025, blends dendroclimatology – the science of reading climate signals in tree growth – with dendrogeomorphology, tracking landslides and rockfalls through scarred bark and tilted trunks. Lead researcher Bency David Chinthala and his team, including experts from Germany and India, analysed rings from Deodhar trees in Batseri, revealing a stark shift: from wetter springs during the Little Ice Age to a parching trend accelerating since the mid-20th century.

“We observed an increase in geohazard activity since the mid-20th century, indicating an increasing vulnerability of slopes to ground failure,” the authors note, underscoring how drier conditions erode soil stability, priming the terrain for monsoon-fuelled mayhem.

Little Ice Age Legacy

Deep in the Deodhar’s heartwood lies a frozen snapshot of the seventeenth and eighteenth centuries, when the Little Ice Age (LIA) cloaked Europe in frost but gifted the Himalayas unusually moist springs. The team’s 463-year tree-ring width chronology, spanning 1558 to 2021 CE, shows robust growth from 1665 to 1757 CE, fuelled by intensified Western Disturbances – extratropical storms barrelling in from the Mediterranean, dumping vital winter snows that melt into spring sustenance.

Correlation analysis linked these rings to the standardized precipitation evapotranspiration index (SPEI04) for February to April, capturing the water balance that Deodhar trees crave. “The significant positive correlation between TRWC [tree-ring width chronology] and SPEI04 for the February-March-April months revealed the combined effect of winter and spring month’s water balance on tree growth,” the study explains.

This wet phase, teleconnected to stronger westerly winds, buffered the region against aridity, allowing thick forests to anchor slopes and sustain apple orchards that now define Kinnaur’s economy. Elders in Batseri recall tales of bountiful harvests, when rivers ran fuller and avalanches were rarer whispers.

Yet, as global temperatures climbed post-1757 CE, so did the drought’s shadow. Tropical ocean warming disrupted moisture inflows, thinning Western Disturbances and leaving springs parched. The reconstructed 356-year SPEI04 timeline paints a grim portrait: moderate to severe dry spells dominating the late nineteenth and twentieth centuries, with recent decades hitting record lows. In Kinnaur, where agriculture hinges on glacial melt and seasonal rains, these shifts spell trouble – wilted crops, shrinking water sources, and a landscape ever more brittle.

Tree Rings as Hazard Harbingers

Deodhar trees don’t just chronicle climate; they bear the scars of survival. By examining tilted stems and impact marks, the researchers mapped 168 years of rockfall activity from 1853 to 2021, identifying 53 events, including eight high-intensity barrages. Astonishingly, these crashes cluster in dry spring years, when sparse vegetation fails to bind soil against summer downpours. “Geohazard activities coincided with dry spring season years,” the paper states, a pattern that intensified after 1960, mirroring a 30 per cent uptick in extreme weather across the Himalayas.

Imagine a Deodhar, its rings swelling in wet years like a deep breath, then gasping thin in droughts. Each narrow band whispers of vulnerability: reduced root grip, cracked earth, and boulders loosened by freeze-thaw cycles. The 2021 Batseri rockfall, which buried paths and grazed homes, fits this narrative – a dry spring prelude to monsoon fury. Chinthala’s team found that such events, once sporadic, now surge, threatening the Indo-Tibetan border’s infrastructure, from hydropower dams to the vital Hindustan-Tibet Road.

This isn’t abstract science; it’s lived peril. Kinnaur’s 80,000 residents, many subsistence farmers, face cascading risks. Droughts curb apple yields – Himachal’s “red gold” – while rockfalls isolate villages, hiking food prices and migration. The study ties these to broader Himalayan woes: glacial lake outburst floods (GLOFs), landslides, and snow avalanches, all amplified by a warming world where spring-summer heatwaves evaporate what little moisture lingers.

Warming’s Western Front

Why now? The paper pins blame on anthropogenic warming, which has cranked Himalayan temperatures by 0.2°C per decade since 1970 – double the global average. “The spring and summer months are becoming more critical for tree growth and ground stability due to unprecedented temperature rise during the last century,” warn the authors. Western Disturbances, once reliable, now falter under shifting jet streams, while El Niño patterns exacerbate dryness.

In India, where the Himalayas cradle 1.5 billion people’s water security, these findings are a clarion call. The PIB release emphasizes integration of tree-ring data into risk models: “The study analyses factors responsible for geohazard activities to enable better prediction of future hazard events and support early warning systems.” BSIP’s work, funded by DST, pioneers this – transforming ancient archives into tools for modern defence.

Slopes Toward Sustainability

As Kinnaur’s Deodhars stand sentinel, their rings urge action. Reforestation with drought-resilient natives, slope-stabilizing terracing, and AI-driven monitoring could blunt the edge. Community-led early warnings, drawing on local lore, might save lives where tech lags.

Chinthala reflects: “Our findings provide a suitable baseline for adapted forest management, sustainability and ground stability measures under ongoing climate warming.” In Batseri, where Deodhars have endured empires and ice ages, hope roots deep. By heeding these arboreal elders, India can rewrite the mountains next chapter – not one of collapse, but resilience. The Himalayas, ever-changing, demand we listen before the next rock tumbles.