Future impact of climate extremes in the Mediterranean: Soil erosion projections when fire and extreme rainfall meet

Climate change projections over the Mediterranean basin point toward an increase in frequency and intensity of extreme events that will directly impact ecosystems resilience. In this study, we evaluated future trends of soil loss in forestland in Catalonia (NE Spain) due to fires and vegetation dynamics, considering the potential future impacts of co-occurring extreme fire and rainfall events, and assessing how fire suppression can contribute to soil erosion mitigation. The process-based MEDFIRE model was used to simulate changes in forestland due to climate and fires between 2011 and 2050 under six different future scenarios that resulted from the combination of two climatic scenarios and three fire management policies. Annual projections on landscape changes were used to estimate soil loss using theUniversal Soil Loss Equation. Projected annual soil losses for forested land in Catalonia ranged between 15 and 16 tons/ha, with scenarios simulating current levels of fire suppression projecting around -5% soil loss than those assuming more relaxed suppression strategies. On average, fires explained 12-16% of annual soil loss in the region, but in fire-severe years, they explained up to 90% of the total annual soil loss. Projected mean total soil loss in years where extreme rainfall and fire meet was 150% higher than in years where both events were not contemporary. The estimated annual probability that the two extreme impacts will co-occur in the future ranged between 0.09 and 0.11 between scenarios. Our results highlight the importance of landscape and fire management in minimizing soil loss and its potential impacts for ecosystems.