Multi-scalar aridity dynamics and climate-vegetation coupling in the Western Himalayan Cold Desert, India

The cold deserts of the Western Himalayas, including Lahaul-Spiti, Kinnaur, and Ladakh, are highly vulnerable to global temperature rise. These high-altitude arid regions experience limited precipitation and extreme temperatures, making them particularly sensitive to changes and variations in dryness. Understanding historical aridity trends is crucial for assessing climate change impacts and developing effective conservation strategies. This study uses data from CRU TS v4.08 to analyse trends in aridity from 1901 to 2022 using the Aridity Index (AI), which is the ratio of yearly precipitation (P) to potential evapotranspiration (PET). Hydroclimatic variability and drought severity were also evaluated using the Standardized Precipitation Index (SPI), Standardized Precipitation-Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI). Based on Aridity Index values, the research region was divided into several climatic zones, on Annual and seasonal basis…. Temporal and seasonal analyses reveal a 13.3% increase in annual Aridity Index, indicating declining dryness-most pronounced in winter due to increased western disturbances-with consistent wetting trends confirmed by positive annual slopes in AI, SPI (0.0104), SPEI (0.0127), and RDI (0.0118). However, increased precipitation in rain-shadow cold deserts could negatively impact soil stability, trigger landslides, and disrupt vegetation adapted to arid conditions, potentially leading to root rot and biodiversity loss. These changes may also pose risks to local communities by increasing infrastructure damage, and vulnerability to natural disasters. Long-term monitoring using Aridity Indices, SPI, SPEI and RDI along with adaptive management strategies, is essential to mitigate negative effects and ensure the sustainable conservation of these fragile ecosystems under changing climatic conditions.