Climate change and forest fires

Antonello Provenzale, Institute of Geosciences and Earth Resources, CNR-IGG, Pisa, Italy

The danger of forest fires in Mediterranean regions is expected to increase in coming decades, owing to drier climatic conditions in summer. A recent study lead by Marco Turco of the University of Barcelona and developed in the framework of ECOPOTENTIAL by Antonello Provenzale e Jost von Hardenberg from CNR, jointly with colleagues from the Universities of Lisbon and California at Irvine, has analyzed available forest fire and climatic data, developing empirical models able to quantitatively estimate the danger of forest fires and the expected amount of burned area based on summer aridity conditions. Most forest fires are triggered by direct human activities, but the extent of the burned area is controlled also by the prevailing climatic conditions.

The variables considered are the summer Burned area (Ba) and the Standardized Precipitation Evapotranspiration Index (SPEI,, an index measuring the difference between precipitation and potential evapotranspiration over a specific period. In general, data show that the BA anomalies follow the SPEI anomalies linearly, that means, if SPEI anomaly (high aridity values) doubles in a given year compared to the previous year, even the BA will tend to be double than the previous year. The impact of coincident drought and antecedent wet conditions on summer BA in Mediterranean Europe is assessed by analyzing the high-quality database provided by the European Forest Fire Information System (EFFIS44) and national archives. The study shows, for the first time, that dry conditions in a given summer lead to a larger Burned Area during the same summer, while summer drought conditions of previous years could reduce BA on the current year by limiting vegetation growth and biomass (fuel availability). Since projections indicate an increase of summer drought conditions, in the following decades a significant increase in the burned area in Mediterranean Europe can be expected. Summer fire risk may increase in the northern Mediterranean regions, such as Italy, France, Catalonia, because the ecosystems are less adapted to cope with drier conditions. The increase in the frequency and intensity of droughts expected in the near future thus may require a rethinking of current fire management strategies. The models developed in this study provide insights in the impacts of climate variability on forest fires, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

Citation: Turco M., von Hardenberg J., AghaKouchak A., Llasat M. C., Provenzale A., Trigo R. M. (2017). On the key role of droughts in the dynamics of summer fires in Mediterranean Europe. Scientific Reports, 7: 81, 2017, DOI:10.1038/s41598-017-00116-9.