Are rapid onset drying events escalating forest fires across India’s ecoregions?

Abstract Rapid onset drying events are emerging as a critical driver of ecological vulnerability across India's diverse landscapes. This study investigated the relationship between these accelerated drying phenomena of flash droughts (FDs) and forest fire occurrence across 43 Indian ecoregions from 1979 to 2023, revealing patterns of escalating forest fire risk. We employed a four-criteria methodology based on the Evaporative Stress Ratio (ESR) to identify and characterize FD events. The criteria included temporal duration (minimum 30 days), severity (SESR ≤ 20th percentile), intensification rate (ΔSESR ≤ 40th percentile), and mean intensification (ΔSESRz ≤ 25th percentile). Our analysis uncovered significant regional variations in event frequency, with mountainous regions showing vulnerability - the Karakoram-West Tibetan Plateau alpine steppe experienced 31 rapid drying events, while the Eastern Himalayan broadleaf forests recorded only 10 events. The temporal analysis revealed clear seasonal patterns, with June being the primary onset month in 17.8% of ecoregions, followed by January and October, each dominating 14% of regions. Critically, 79.1% of ecoregions showed increasing forest fire trends from 2001 to 2023, with the Orissa semi-evergreen forests displaying significant vulnerability. High-altitude and semi-arid regions showed statistically significant positive correlations between rapid drying frequency and fire incidents (r = 0.68, p = 0.002 in Karakoram-West Tibetan Plateau alpine steppe; r = 0.59, p = 0.004 in Thar desert), suggesting that accelerated moisture depletion creates conditions conducive to fire outbreaks in these vulnerable ecosystems. Most ecoregions experienced these drying events for 1-2% of the study period, indicating that even brief episodes of rapid desiccation can trigger lasting ecological impacts. These findings highlight the urgent need for integrated drought-fire management strategies that account for the unique challenges posed by rapid onset drying events in different ecological contexts.