Abstract
A record 500,000 hectares burned in Portugal during the extreme wildfire season of 2017, with more than 120 human lives lost. Here we analyse the climatic factors responsible for the burned area (BA) from June to October series in Portugal for the period 1980–2017. Superposed onto a substantially stationary trend on BA data, strong oscillations on shorter time scales were detected. Here we show that they are significantly affected by the compound effect of summer (June-July-August) drought and high temperature conditions during the fire season. Drought conditions were calculated using the Standardized Precipitation Evapotranspiration Index (SPEI), the Standardized Precipitation Index (SPI) and the Standardized Soil Moisture Index (SSI). Then the extent to which the burned area has diverged from climate-expected trends was assessed. Our results indicate that in the absence of other drivers, climate change would have led to higher BA values. In addition, the 2017 extreme fire season is well captured with the model forced with climate drivers only, suggesting that the extreme fire season of 2017 could be a prelude to future conditions and likewise events. Indeed, the expected further increase of drought and high temperature conditions in forthcoming decades, point at a potential increase of fire risk in this region. The climate-fire model developed in this study could be useful to develop more skilled seasonal predictions capable of anticipating potentially hazardous conditions.
Highlights
Every year, wildfires impact the lives of many people worldwide
Society exposure to large wildfires has increased as a result of a significant increase in Wildland-Urban Interface (WUI)[5,6]
The solid association of burned area (BA) with these factors ascribe that the process by which climate influences BA is, overall, straightforward: drier and warmer conditions result in larger wildfires
Summary
Wildfires impact the lives of many people worldwide. These devastating natural disasters cost billions of Euro in direct and indirect damages. In October, several fires in California were responsible for more than 85 casualties with the vast majority of these taking place in a single fire event in northern California (Camp Fire) that burned more than 10000 homes in the town of Paradise[2] Both the occurrence of and changes in climatic extremes constitute a great concern to fire impacts[3,4]. Mediterranean ecosystems are prone to forest fires[16] and a number of extreme fire seasons have struck both the western (2003) and the eastern (2007) Mediterranean and were associated with unusually intense heatwaves[10] These fires (with an average of approximately 4500 km[2] burned area every year) caused a massive impact on the economy and the environment, with substantial impacts to carbon sequestration, existence of raw materials, and human casualties[13]. Smoke from forest fires is composed of hundreds of chemicals, many of which are known to affect air quality and be harmful to human health[22,23], and contribute to climate change[24]
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