Latitude or altitude as the future refugium? A case for the future of forests in Asia Minor and its surroundings

At the current juncture with climate change, centennial projections of species distributions in biodiversity hotspots, using dynamic vegetation models may provide vital insight into conservation efforts. This study aims to answer: (1) if climate change progresses under a business-as-usual scenario of anthropogenic emissions for this century, how may the forest ranges be affected? (2) will there be potential regional extinctions of the taxa simulated? (3) may any site emerge as a potential refugium? Study Area: Anatolian Peninsula and its surroundings, longitudes 24-50 degrees E, latitudes 33-46 degrees N. Time Period: 1961-2100. Major Taxa Studied: 25 woody species and a C3 grass-type. Method: Keeping a spatial window large enough to track potential changes in the vegetation range and composition especially in the mountain ranges within the study area, we parameterized a process-based regional-to-global dynamic vegetation model (LPJ-GUESS v 4.1), forced it with ERA5-Land reanalysis for the historical period, and five different bias-corrected centennial global circulation model (GCM) datasets under SSP5-8.5, and simulated the dynamic responses of key forest species. Bivariate spatio-temporal maps from the simulation results were constructed for final analysis. Results: A significant increase in woody taxa biomass for the majority of our study area, towards the end of the century was simulated, where temperate taxa with high tolerance for drought and a wider range of temperatures took dominance. The mountain ranges in our study area stood out as critical potential refugia for cold favoring species. There were no regional extinctions of taxa, however, important changes in areal dominance and potential future forest composition were simulated. Main Conclusions: Our simulation results suggest a high potential for future forest cover in our study region by the end of the century under a high emissions scenario, sans human presence, with important changes in vegetation composition, including encroachment of grasslands ecosystems by woody taxa.

Determining potential eco-refugia or any future range shift for woody taxa requires a clear assessment of what an uncertain future may hold for these potential climate change mitigators in their native ranges. By means of a process-based dynamic vegetation model and high resolution climate data, we simulated the potential forest ranges for the Anatolian Peninsula and its surroundings, sans human presence, for 25 key forest species and a grass-type, keeping a close watch on the mountain systems to assess their potential as eco-refugia for sensitive taxa. Our simulation results suggest important centennial changes in vegetation composition in favor of the temperate taxa for our study area, a potential woody species encroachment into steppe ecosystems, and an altitudinal prioritization for potential migration of the boreal taxa rather than a latitudinal one for a temporal window of 140 years.image