Forested Natura 2000 sites under climate change: effects of tree species distribution shifts

Abstract. Climate change can have severe impacts on tree species distributions. Models consistently show that tree species will follow climate towards higher elevations and latitudes. This has various effects on forest ecosystems. Forests have a slow dynamic compared to other ecosystems and are affected severely by tree species distribution shifts. Forested conservation areas with limited management reveal a slow adaptation process to a changing climate. In this study, we have modelled and analysed the effect of possible tree species distribution shift in Norway spruce (Picea abies), European beech (Fagus sylvatica), and two oak species (Quercus petraea and Quercus robur), considered jointly on forested Natura 2000 sites, an EU-wide conservation area network. The modelling procedure was performed using 3 to 4 bio-climatic variables derived from 26 variables of the EURO-CORDEX Coupled Model Intercomparison Project Phase 5 (CMIP5) climate simulations for the Representative Concentration Pathways (RCPs) 2.6, 4.5, and 8.5 until 2098. Our results reveal a severe decline in Picea within Natura 2000 sites in central Europe and lower elevations and confirm a strong shift towards higher elevations and latitudes. This amounts to an 18 % absolute mean change (−18 % mean loss, 15 % mean gain). Quercus sp. reveal similar results, with 23 % absolute mean change (−23 % loss, 24 % gain) at Natura 2000 sites, whereas Fagus remains stable throughout the model results with 8 % absolute mean change (−7 % loss, 9 % gain). The best model algorithms for all species were the generalised additive models (GAMs). As ecosystems of any type are highly dynamic, climate change can lead to additional severe pressure on statically defined conservation goals and associated management activities.