Changes in the recent habitat suitability of Euro-Mediterranean Anopheles species due to land-use and climate

Background: Habitat suitability of Anopheles mosquitoes depends on appropriate climate and land-use conditions. Anopheles are the main vectors for malaria transmissions in the Euro-Mediterranean region. There is major concern that there will be a spread or shift of Anopheles species due to the expected climate and land-use change. This study aims to identify the main climate and land-use drivers for changes in the habitat suitability for six different Anopheles species between 2000 and 2020 within the Euro-Mediterranean region. Methods: Boosted Regression Trees were applied to establish the link between climate and land-use predictors and habitat suitability. An ensemble of 16 models, based on different methods of selecting background points and statistical predictors, was applied to each species. The ensemble was evaluated by means of model skill and transferability to identify the best model. Under consideration of contribution, interactions and response range, the most important predictors and those responsible for changes were identified. Results: The model ensembles agree on the direction of change for four species within the study area, with two showing an overall increase ( An. atroparvus, An. sacharovi ) of areas with suitable conditions and two showing a decrease ( An. messeae, An. sergentii ). Climate change is mainly responsible for shifts in the habitat suitability. Only a few models attribute changes mainly to land-use. The limited influence of land-use changes may be due to the too coarse spatial resolution. For most species, temperature-related bioclimatic variables (BIO4, BIO5, BIO8) are the most important predictors for changes in habitat suitability. A superior method for either the specific background points or predictor selection did not emerge, because they depend on the species analyzed. Conclusions: Between 2000 and 2020, rising temperatures were the main driver of changes in the habitat suitability of the Anopheles species in the Euro-Mediterranean region, with land-use changes having a relatively minor impact. Especially regions to the north of the distribution area are characterized by a greater habitat suitability, while regions to the south show decreasing trends. This may also impact the risk of local malaria transmission in these regions.