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

Pradyumna Rajashekar; Aparna Krishnan; Varun Varma; Jayashree Ratnam; Mahesh Sankaran; Caroline E. R. Lehmann

doi:10.1071/WF24174

RESEARCH ARTICLE (Open Access)

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

Pradyumna Rajashekar ^A ^# , Aparna Krishnan ^A ^# , Varun Varma

^B , Jayashree Ratnam

^A ^* , Mahesh Sankaran

^A and Caroline E. R. Lehmann

^C ^D

+ Author Affiliations

- Author Affiliations

^A National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bengaluru, Karnataka 560 065, India.

^B Rothamstead Research, AL5 2JQ, Harpenden, UK.

^C Taxonomy and Macroecology, Royal Botanic Garden Edinburgh, Edinburgh EH3 5LR, UK.

^D School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FF, UK.

^* Correspondence to: j.ratnam.bangalore@gmail.com

International Journal of Wildland Fire 34, WF24174 https://doi.org/10.1071/WF24174

Submitted: 16 October 2024 Accepted: 8 May 2025 Published: 11 June 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

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 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 wet (2001–2010) and dry decade (2011–2020).

Key results

Across both decades, savannas burned more frequently and over larger areas than forests. Burnt area and fire frequency in both habitats were higher in the wet decade. Human modification was the major driver of fire occurrence in the wet decade, but MAR took on greater importance in the dry decade.

Conclusions

Savannas and forests in the NBR have differing fire regimes. During dry periods, these systems are fuel limited and 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.

Keywords: fire management, forests, savannas, Southern India, traditional burning practices, Western Ghats.

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