Forest fire regimes and their ecological effects in seasonally dry tropical ecosystems in the Western Ghats, India

Abstract

The Western Ghats in India is one of 25 global hotspots of biodiversity, and it is the hotspot with the highest human population density. Disturbances such as forest fires are almost annual events in deciduous ecosystems. This study considers variations in the regional fire regime that are related to vegetation type and past human disturbances in a landscape. Using a combination of remote-sensing data and GIS techniques, burnt areas were delineated in three different vegetation types, and various metrics of fire size were estimated. Belt transects were enumerated to assess the vegetation characteristics and fire effects in the landscape. Temporal trends suggest increasingly short fire return intervals (FRIs) across the landscape. In the dry deciduous forest the mean FRI is 6 years, in the tropical dry thorn forest mean FRI is 10 years, and in the tropical moist deciduous forest, mean FRI is 20 years. Tropical dry deciduous forests burned more frequently and had the most fires in any given year as well as the single largest fire (9,900 ha). In the tropical moist deciduous forests, tropical dry thorn forests, and tropical dry deciduous forests, 70%, 56%, and 30% respectively, have not burned during the seven years that were analyzed (1996, 1997, 1999, 2001, 2002, 2004, 2005). Forest fires had significant impacts on species diversity and regeneration in both tropical dry and moist deciduous forests. The short FRI in tropical dry deciduous ecosystems, and increased susceptibility of tropical moist deciduous forests to fires run the risk of continued erosion of species composition, structure, and regeneration within these forests. The current precolonial policy of fire management must give way to a more people-centered policy that acknowledges the use of fire in the landscape if these forests are to be conserved.