The 2010-2015 Megadrought and its influence on the fire regime in central and south-central Chile

Forest fire activity has increased in recent years in central and south-central Chile. Drought conditions have been associated with the increase of large wildfires, area burned and longer fire seasons. This study examines the influence of drought on fire regimes and discusses landscape management opportunities to decrease fire hazard. Specifically, we investigate the effect of the 2010-2015 Megadrought (MD) compared to 1990-2009 period on fire activity (fire-season length, number of fires and burned area across months, fire sizes, regions and vegetation cover types, simultaneity, and duration of fires) in central and south-central Chile (32 degrees-39 degrees S), using contemporary fire statistics derived from the Chilean Forest Service. For large fire events (>200 ha) the average season length increased by 67 d (44%), comparing 2010-2015 to 1990-2009. Earlier and later ignition dates resulted in extended fire seasons in MD years. During the MD, the number, area burned, simultaneity, and duration of large fires increased significantly compared to the control period, including the unprecedented occurrence of large fires during winter. The burned area in large fires increased in all vegetation types, during the MD compared to the control period, especially in the exotic plantation cover type. The regions that were most affected by fire (i.e., total area burned) during the MD were Maule, Bio-Bio, and Araucania (35-39 degrees S) that concentrate >75% of forest plantations in Chile. Although both maximum temperatures and precipitation are drivers of fire activity, a simple attribution analysis indicates that the sustained rainfall deficit during 2010-2015 was the most critical factor in the enhanced fire activity. Future climate change predictions indicate more recurrent, intense, and temporally extended droughts for central and south-central Chile. Under this scenario, land-use planning and fire and forest management strategies must promote a more diverse and less flammable landscape mosaic limiting high load, homogenous, and continuous exotic plantations.