Assessing ecosystem services resilience to drought and its drivers in mediterranean forests using a counterfactual, process-based modelling approach

Forests cover ca. 30% of land surface, host much of Earth’s biodiversity, and provide many ecosystem services to humans. As global environmental change alters ecosystems at fast rates, we still have a limited understanding of how forests and their services may respond to anthropogenic and natural disturbances. The resilience framework represents a powerful approach for assessing forests’ ability to withstand pressures and understand how to preserve biodiversity and human well-being. Here we used a process-based model and forest inventory data to estimate five forest ecosystem services (FES) (bluewater provision, erosion mitigation, potential recreational value, timber volume stock, carbon stock) and assess their resistance and resilience to the severe drought that affected Catalonia in 1994. Specifically, we estimated annual FES from 1990 to 2020 under three scenarios, i.e., actual (including 1994 drought), extreme (increasing drought by 50%), and counterfactual (undisturbed), and then quantified resistance and resilience as the log-ratio of FES under the actual or extreme scenario relative to the undisturbed scenario in 1994 and integrated over five years following the drought, respectively. Catalan forests withstood historical drought conditions yet faced substantial damage under the extreme scenario. Resistance and resilience varied among FES, with hydrologically related services showing sharper declines but quicker recoveries than services that directly depend on forest structure and stocks. Local drought intensity was the primary driver of resilience, while forest structure had service-specific effects. These findings underscore the importance of evaluating a broad range of ecosystem services to capture diverse responses to drought and inform management strategies to sustain key forest functions under increasingly extreme climate conditions.