Shimla, Dec 11 (PTI) Deodar trees in picturesque Sangla valley of Himachal’s Kinnaur district have unfolded a shift from wetter spring conditions during Little Ice Age (LIA) to progressive drier conditions since 1757 AD with noticeable increase in spring drought years in recent decades.
A study conducted by the Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute of the Department of Science and Technology (DST), following rock fall incidence near Batseri village in the district in July 2021, in which several deodar trees were damaged, analysed factors responsible for the geohazard activities to enable better prediction of future hazard events to support early warning systems.
According to an official statement issued by the Ministry of Science and Technology on Thursday, the study based on past climates using dating of annual growth layers in trees (dendroclimatology and dendrogeomorphology) underscored the need for robust reconstructions of past hydroclimatic variability and related geohazard episodes in view of increasing frequency of extreme climatic events.
The extreme climate events include droughts and floods and their strong association with geohazards like landslides, glacial lake outburst flood (GLOFs), rock falls and snow-avalanches, especially in the Himalayan area.
Dendroclimatology is the science of using information from tree rings to study and reconstruct past climate conditions while Dendrogeomorphology is the science of using growth anomalies and disturbances in tree-ring records to date and understand past geological and geomorphological processes.
Tree-rings, which are layers of new wood that form each year, providing a record of the tree’s age and past environmental conditions act as natural archives to such climatic and geohazard events, offering the potential to bridge this knowledge gap due to absence of long-term high-resolution records and stirred the need to understand the interactions between moisture variability and geohazard dynamics from the Himalayan region, the study said.
The study showed that tree growth is highly sensitive to spring months’ (February to April) moisture, primarily influenced by winter precipitation derived through Western Disturbances (WDs).
A total of 53 rock fall events, including eight of high intensity, were linked to dry spring conditions, especially after year 1960, indicating climate-induced ground instability while the spring drought conditions led to slopes with poor vegetation cover, exposing them to vulnerability when the dry conditions are followed by the intense summer monsoon rainfalls.
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 provided insights on how climate variability, specially the spring and pre-monsoon summer droughts trigger geohazards in the vulnerable Himalayan regions, the statement said. PTI BPL AMJ AMJ
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