Ecological niche modelling of three Mediterranean pine species in the south of Spain: a tool for afforestation/reforestation programs in the twenty-first century

Climate change models predict an increase in aridity in many parts of the world for the twenty-first century, which is likely to be more intense in the Mediterranean basin than in other regions. This study addresses the potential distribution of three Mediterranean pine species (Pinus pinea L., P. halepensis Mill. and P. pinaster Aiton) in southern Spain in response to the forecast increased aridity. Pines constitute a useful source of various types of raw materials, which has led to their increasing introduction around the world. The study was based on ecological niche modelling using multinomial logistic regression, over an area spanning about 8.7 million ha in the south of Spain. In total, 11 explanatory variables were included, drawing on measurements made at high resolution (200 m). Four different periods were studied: the reference period (1961–2000), early twenty-first century (2011–2040), middle twenty-first century (2041–2070) and late twenty-first century (2071–2100). Future time slices were analysed in three different scenarios: B1, A1b and A2 in the CNCM3 general circulation model. The results predict a wider distribution for stone pine, which could expand its potential area in southern Spain. In contrast, Aleppo pine, and especially cluster pine, would reduce their present distribution, with cluster pine occupying higher altitude sites while low altitude populations diminished. The validation model enables accurate maps to be produced, representing powerful tools for afforestation/reforestation programs in the future.