Redistribution of Crop Bioclimatic Analogues in Portugal Under Future Climate Scenarios

Climate change poses severe threats to agricultural systems in the Mediterranean Basin. Portugal is particularly exposed and vulnerable to projected warming and drying trends. This study provides a high-resolution bioclimatic characterisation of six Portuguese crops: grapevine, olive, wheat, maize, potato and tomato. Bioclimatic indicators (BIOCLIM) based on the CHELSA V2.1 km scale data for the historical period (1981–2010), as well as ensemble mean projections for 2041–2070, under SSP1-2.6 and SSP5-8.5, are used for this purpose. For each crop, all 19 BIOCLIM variables were extracted over the present cultivated area and subjected to Principal Component Analysis (PCA) to characterise the multivariate bioclimatic space. Future suitability was assessed using a multivariate envelope criterion requiring the PCA space to remain within the present observed range. In addition to area loss within current cultivated extents, potential gain areas, which refer to locations outside current cultivation but within the bioclimatic envelope, were identified across mainland Portugal. Under SSP1-2.6, losses ranged from 37 to 41% of the present cultivated area, whereas, under SSP5-8.5, losses ranged from 52 to 61%, with all six crops losing more than half of their present bioclimatic niche. Concurrent gains were, however, identified in northern Portugal and, at higher elevations, reflecting a northward and altitudinal shift in bioclimatic suitability. Once these gains are offset against losses, the net change in the suitable area ranged from −12% to −29% under SSP1-2.6, with maize alone expanding (+17%), and from −15% to −49% under SSP5-8.5. These projections do not account for future crop adaptation through physiological acclimation, cultivar improvement, or changes in management practices. Nonetheless, these results provide an impact assessment framework to support climate adaptation planning in Portuguese agriculture.