Key relevant ecosystem services provided by Mediterranean forests in Catalonia region show lower values of potential supply nowadays than in 1990. During the last 25 years, ecosystem services in Catalonia such as climate regulation through carbon sequestration, timber and water provision declined consistently in this Mediterranean region.
These results emerged from the report “FOREStime: changes in the ecosystem services of Catalonian forests during the last 25 years”. This study was partially funded by the Catalan Office for Climate Change (OCCC) and developed by a multi-disciplinary team including researchers from several research institutions in Catalonia (CREAF, CTFC, CSIC, Autonomous University of Barcelona, and University of Lleida).
The study took advantage of an extensive database of 3,417 permanent plots from the Spanish National Forest Inventory network and applied a series of ecological models to quantify five ecosystem services in the year 1990 and in 2015.
Lower levels of climate regulation and timber and water provision
Mediterranean forests have been influenced by human activities for millennia and are increasingly affected by multiple drivers related with global change. Since mid-20th century, lower levels of direct human pressure on many of these forest systems, as well as agricultural abandonment, have led to forest and tree species expansion, and to changes in forests structure and productivity.
The results obtained showed different temporal dynamics for the five forest ecosystem services assessed, with different levels of spatial heterogeneity and a predominantly declining trend in water provision (-30%), timber provision (-7%) and climate regulation (-17%) since 1990. Food provision (wild and edible mushrooms) showed contrasting patterns in different ecoregions (increases in coastal and montane, decline in inland areas), and erosion migration showed an increase across inland and montane regions.
The results showed the key effect of forest structure on the ecosystem services analysed and their temporal dynamics. In general, those plots with higher levels of stand basal areas and smaller trees (lower mean DBH) in 1990 showed stronger ecosystem services declines. On the other hand, impacts of recent drought events or climate anomalies on ecosystem services changes were relatively minor.
The study also reported on potential trade-offs between water supply and the other ecosystem services analysed, which became more evident when changes in ecosystem services were assessed than when static data were used, reinforcing the relevance of addressing temporal dynamics in ecosystem service assessments.
The negative trend in most of the ecosystem services assessed in the study and also the predominant characteristics of the forests studied (i.e., density and high levels of competition for resources) suggest that this decline in ecosystem services could continue over the coming decades. However, the strong influence of forest stand structure and development, which is primarily management-driven, suggests that regional planning and local forest practices play a role in enhancing those ecosystem services.