Precipitation - fire linkages and variability in continental-scale fire carbon emissions

Abstract:

The link between drought and fire is not universal because for fires to occur rainfall is needed for fuel build-up but drought is required to make vegetation ignitable. We present an overview of how precipitation patterns and changes therein have shaped spatial and temporal variability in fire occurrence and associated carbon emissions over the past 17 years, using the latest version of the satellite-derived Global Fire Emissions Database (GFED4). We start in tropical savannas where there is a clear dualistic relation between precipitation and fire and show how trends and interannual variability in rainfall have modified annual emissions in Africa and Australia. Because savannas are the main source of fire carbon emissions, this variability can be seen in atmospheric abundances of several trace gases. We then zoom in on tropical forest regions and show that the link between drought and fire activity is most pronounced in the Indonesian archipelago where tropical peatlands require prolonged droughts to burn. Highest emissions occurred there in 1997-1998 when a strong El Niño hit the region, but also moderate drought years have boosted fire activity here more recently. Recent Amazonian droughts in 2005, 2007, and 2010 also led to increased fire activity in forested regions in South America, mostly in degraded lands and offsetting some of the reductions in carbon emissions from deforestation achieved in Brazil. Finally we focus on the boreal region, where potentially large climate-carbon feedbacks are present due to the strong linkages between drought and fire in combination with climate change and arctic amplification.