Climatic drivers for summer and winter wildfire burned area in northern Italy

The Mediterranean region is a focal point for wildfires. Climate change is projected to affect the Mediterranean hydrological cycle, resulting in intensified drought conditions and increased fire hazard. Even though northern Italy is rich in water resources, wildfires have become increasingly prevalent in recent decades, occurring not only during the summer but also in the winter season.

This study explores the climatic drivers influencing the monthly burned area (BA) during both summer and winter fire seasons in northern Italy from 2007 to 2022.

The GPS-based BA perimeters analysed here are provided by the monitoring campaigns performed by the Carabinieri Command of Units for Forestry, Environmental, and Agri-food protection. For each summer ( May - October) and winter (November -April) fire season, the monthly percentage of burned area at 0.11 degrees of resolution for the 2007-2022 period was obtained. A total of 150 daily precipitation and maximum and minimum ground station series were collected, converted at monthly scale, reconstructed, homogenised and spatialised at 0.11° resolution by mean of Universal Kriging with auxiliary variables. Subsequently, several climatic indices were computed for precipitation (Precipitation, Consecutive Dry Days (CDD) and Consecutive Wet Days (CWD)), temperature (Maximum and Minimum Temperature and Potential Evapotranspiration (ET₀)) and drought (Standardised Precipitation Index (SPI) Standardised Precipitation Evapotranspiration Index (SPEI) and Water Balance (WB)). The Pearson’s correlation test between the detrended monthly time series of BA and of climatic indices was performed for each pixel and for both the summer and winter seasons. Only the strongest and significant correlations between BA and climatic indices  were retained to identify the best BA predictors. Based on the CORINE Land Cover map, for each season the vegetation classes that were most susceptible to wildfires, and their typical elevation ranges, were identified.

This study highlights different types of behaviour between summer and winter wildfires. Specifically, summer fires predominantly affect vegetation classes located in the plains, such as evergreen broadleaf forests and natural vegetation mixed with croplands. By contrast, winter wildfires target deciduous broadleaf forests located between 800 and 1000 m. a.s.l..