Assessing cost-effectiveness of land management measures to restore forest ecosystem services after fire using hydrological modelling and multi-criteria decision analysis

Forest fires strongly disturb key hydrological ecosystem services, such as soil protection, streamflow regulation and clear water provisioning, which can affect ecosystems and communities in burnt areas and downstream. Post-fire soil and water conservation (SWC) measures can be expensive, and their effectiveness depends on multiple factors such as the nature of the measures, the targeted areas, and the extent of their application. However, different biophysical and socioeconomic effectiveness criteria are rarely assessed comparatively. This study aims to assess the costs and effectiveness of six SWC measures to mitigate soil erosion and stream water contamination (using sediment yield as proxy): post-fire mulching with straw and forest residue, contour-felled logs, straw wattles, contour bunds and riparian buffers. It was conducted for a wildfire in 2003 in the Odiáxere catchment, southern Portugal. Costs were assessed from the literature and their validity confirmed by consulting an expert panel. Effectiveness was assessed using the hydrological and erosion model OpenLISEM. Measures were compared using a Multi-Criteria Decision Analysis, including criteria such as effectiveness, application costs, and other social costs. Four sets of criteria weights were tested, based on the individual perspectives of soil conservation experts, land managers, and water managers, as well as a combination of the three. Straw mulching was the best performing SWC measure from most perspectives, although closely followed by forest residue mulching and contour-felled logs. However, riparian buffers were the best measure from the water management perspective, with a much better performance than the others. The results illustrate how different intervention objectives affect the cost-effectiveness of each SWC measure. This approach can help forest and water managers, local administrators and environmental stakeholders with different objectives and mandates, to discuss and select the most appropriate SWC measures to mitigate the impacts of forest fires on ecosystem services according to local intervention priorities.