Effects of biodiversity loss and restoration scenarios on tree-related ecosystem services

In landscapes worldwide, trees in forests and agricultural lands have important ecological functions. Their loss may have important consequences for the delivery of ecosystem services (ES) to local communities, even if individual trees have low conservation values. This study explores the effect of land use and land use change on the provisioning of tree-related ES in a mixed Afromontane landscape in Ethiopia. First, we mapped the current distribution of tree-related ES using indicator ES, which represent the most characteristic ES for different land use types. More ES were characteristic for indigenous forest and agroforest, compared to exotic forest, cropland, and rangeland. A scenario analysis was conducted on the effect of tree species loss and restoration (RES) on ES. Two ES indices, ES diversity and ES multifunctionality, were used to evaluate the ES supply. The different behavior of the two ES indices in the species loss scenarios suggests that rare species have distinct traits that provide specific ES, which could not be compensated by the remaining common species. In tree species-poor landscapes, local communities prefer multifunctional tree species and these keep the diversity of ES supply high. Overall, our findings demonstrate that future conservation and restoration programs in mixed landscapes should both protect a large diversity of tree species, including rare tree species, and promote multifunctional keyston species to ensure a long-term and diverse ES supply.