Decadal scale fire dynamics in savannas and forests of the Nilgiri Biosphere Reserve, India

Background The Nilgiri Biosphere Reserve (NBR) in the Western Ghats, India, contains a mosaic of savannas and forests. This landscape experiences wildfires regularly, but we lack an integrated understanding of factors driving fire regimes in the region. Aims To examine the effects of climate, vegetation and human activity on wildfires in the NBR. Methods Using remotely sensed datasets, we examine how mean annual rainfall (MAR), topographic complexity and human activity influence fires in savannas and forests of the NBR across a dry (2001-2010) and wet decade (2011-2020). Key Results Across both decades, savannas burned more frequently and over larger areas than forests, with human modification emerging as a key driver of fire. Burnt area and fire frequency in both habitats were higher in the wet than the dry decade, with MAR taking on greater importance than human modification in driving fire occurrence in the dry decade. Conclusions Savannas and forests in the NBR have contrasting fire regimes. During dry periods, these systems are fuel limited and thus MAR best describes the occurrence of fires. During wet periods when fuel is not limiting, proxies for anthropogenic ignitions best explain fire occurrence. Implications Climate, vegetation and humans collectively determine fire regimes in the NBR. Fire management must integrate across all these factors at the landscape scale to be effective.