Trends in evergreen oak suitability from assembled species distribution models: assessing climate change in south-western Europe

The expected changes to the environmental conditions have concerned the scientific community over the last few decades. A rise in the mean temperature and a variation in rainfall patterns could modify the current distribution of plant species. In this study, we analysed four evergreen oaks (Quercus ilex subsp. ilex, Q. ilex subsp. ballota, Q. suber and Q. coccifera) by means of species distribution models. Three algorithms were used: maximum entropy, logistic regression and environmental distance. Taxa occurrences were taken, chiefly from the National Forest Inventories, and climate data was retrieved from the WorldClim 1.4 project. The present period and four future scenarios were studied. The latter were carried out by averaging thirteen global circulation models (GCMs). Area under the curve was used for validating the models. Maps indicating the suitability and cosuitability among the evergreen oaks were developed. The potential distribution of evergreen oaks in the present period was found to be wider than the actual distribution. Simulations indicate that climate change would increase the cosuitability of western temperate areas for Mediterranean oaks. The use of different algorithms and GCMs, as well as the high validation values obtained, make the study robust. Oaks are an important source of income, especially Q. ilex subsp. ballota and Q. suber. Our findings contribute to our understanding of the dynamics of oaks, and can be considered for management programmes aimed at conserving this natural heritage.