Deodhar Trees in Himachal Pradesh Reveal a Story of Climate and Danger in the Himalayas

Deodhar trees in Batseri, a scenic village in the Sangla Valley on the Baspa River in Himachal Pradesh, reveal a record of a shift from wetter spring conditions during the Little Ice Age (LIA) to progressively drier conditions since 1757 CE, with increased spring drought years in recent decades, as recorded in their rings.

The study analyses the factors that drive geohazard activity, thereby enabling better prediction of future events and supporting early warning systems.

The increasing frequency of extreme climatic events, such as droughts and floods, and their strong association with geohazards such as landslides, glacial lake outburst floods (GLOFs), rockfalls, and snow avalanches, especially in the Himalayan region, underscores the need for robust reconstructions of past hydroclimatic variability and associated geohazard episodes.

Deodhar trees are majestic evergreen conifers native to the western Himalayas, and they thrive in cool, moist mountainous regions across India, Pakistan, Afghanistan, and Nepal. It is the state tree of Himachal Pradesh, a northern hilly state of India. 

Tree rings, which are annual layers of new wood, provide a record of a tree’s age and past environmental conditions and serve as natural archives of climatic and geohazard events, offering the potential to bridge this knowledge gap.

The idea was further motivated by the lack of long-term, high-resolution records and the need to understand the interactions between moisture variability and geohazard dynamics in the Himalayan region.

A rockfall episode in July 2021 near the village of Batseri in Kunnaur, Himachal Pradesh, led the Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute of the Department of Science and Technology (DST), to explore past climates using the dating of annual growth layers in trees (dendroclimatology and dendrogeomorphology).

Fig.1. Google Earth image and ground photographs from the study area, Batseri, Kinnaur. (a) Red dots indicate the location of collected, rockfall-impacted Cedrus deodara trees from a hazard-prone slope (catchment area marked with a white lined area) opposite Batseri village. The yellow circle indicates the location of a bridge and a house damaged by a rockfall in July 2021. (b) View of the rockfall-prone slope and Deodar trees. (c) The damaged house and the reconstructed bridge after the July 2021 incident.

They integrated dendroclimatology and dendrogeomorphology for future risk assessments and mitigation strategies. 

Tree-ring analysis of Deodhar trees (Cedrus deodara) helped reconstruct a 378-year (1558-2021 CE) spring-months moisture history and an 168-year (1853-2021 CE) rockfall activity record at Batseri, Kinnaur, Himachal Pradesh, western Himalayas.

The study showed that tree growth is susceptible to spring months’ (February to April) moisture, primarily influenced by winter precipitation derived through Western Disturbances (WDs).

A total of 53 rockfall events, including 8 of high intensity, were linked to dry spring conditions, particularly since 1960, indicating climate-induced ground instability. The spring drought conditions led to slopes with poor vegetation cover, increasing their vulnerability when the dry conditions are followed by intense summer monsoon rainfall.

Fig. 2.  (a-c) Photo of Batseri village located on a talus fan at the left bank of the Baspa River. (d) Examples of trees injured and broken by boulders. Pictures taken from the upper slope on the right bank of the Bapa River opposite Batseri village.

The findings highlight the critical role of climate variability, driven by regional and global factors, in triggering the geohazards, underscoring the need for forest management, monitoring, and early warning systems.      

This study, published in the journal Catena, enhanced our understanding by providing insights into how climate variability, particularly spring and pre-monsoon summer droughts, triggers geohazards in vulnerable Himalayan regions.

Such findings help local communities and policymakers plan for sustainable land use, improve forest and water resource management, and implement slope stability measures.

This approach can reduce infrastructure damage, protect livelihoods, and enhance disaster preparedness. Moreover, such an approach empowers communities to adapt to climate change and mitigate its impacts on their environment and economy.