We found changes in species range sizes parallel to the severity of the scenarios. Approximately 20% of the species currently present in Germany lost more than 75% of their current range under GRAS, 11% under BAMBU and 7% under SEDG averaged across models.
However, projected range changes showed variations across models. For GRAS, 0% (RF), 4% (GAM) and 5% (GLM) of the currently observed species were projected absent by 2080. The number of currently absent species shifting their ranges to Germany also differed between methods. While RF projected that all 295 species would find suitable conditions in Germany, GLM and GAM were selective and projected roughly half of the species to occur in Germany (42–53%, respectively, across scenarios). Results of local species loss and gain for the 2995 grid cells in Germany coincide with the severity of the scenarios (). The rate of loss per degree of temperature change increased from SEDG to BAMBU to GRAS, while the rate of gains slowed down, indicating nonlinear responses in species numbers (figure S4 in the electronic supplementary material). The spatial distribution of change generally showed considerable variation. In particular, the southwestern and eastern parts of Germany were affected by high rates of turnover and loss (). The spatial pattern of gain was substantially different. Mainly, the central and southern parts of Germany were affected by species gains. Projected SR in the full migration case varied substantially across scenarios (). Under BAMBU (exception RF) and GRAS, SR estimates significantly decreased while under SEDG, median SR significantly increased in all models. Under the assumption of no dispersal, SR decreased significantly in all models (p<0.05, paired Wilcoxon signed-rank test). In addition, range restrictedness increased. When comparing current and future range-size rarity indices, we found a significant increase within all models and across scenarios (p<0.05, paired Wilcoxon signed-rank test; figure S5 in the electronic supplementary material).
Estimated mean ±s.d. of species loss, gain and turnover rates in 2051–2080 relative to 1961–1990 for different scenarios and models in Germany under universal dispersal.
Figure 1 Percentages of species (a) loss, (b) gain and (c) turnover from GLM (6′×10′) for the GRAS scenario for Germany. Modelled estimates of loss, gain, turnover across models (GLM, GAM and RF) showed high agreement (table S2 in the electronic (more ...)
Figure 2 Estimated change in SR (a) using no limitation in species dispersal and (b) with limitation in dispersal computed as difference between modelled future and current SR per grid cell (n=2995 grid cells, 845 species). White boxes, SEDG; light grey boxes, (more ...)