Climatic suitability of Portuguese grapevine varieties and climate change adaptation

Grapevine varietal suitability is strongly linked to regional environmental conditions and growers tend to select varieties that are best suited to these conditions. A high agreement between current growing regions and optimal climatic zones is thus anticipated for a given variety. A changing climate is, however, expected to impose new challenges to this long-term varietal selection. The present research examines the spatial distribution of the main grapevine varieties in Portugal, establishing current and future optimal climatic zones for each variety. The spatial locations of 44 varieties are assessed, and their growing degree-day (GDD) requirements are computed using a high resolution climatic dataset (<1 km). A clustering methodology is applied to the spatial patterns of the optimal GDD of each variety, leading to three varietal groupings (early, intermediate and late). Future changes (2041-2060) in those patterns are then analysed using a 17 model-ensemble and two scenarios (RCP4.5 and 8.5). Results indicate that Portuguese varieties have high adaptability, because they are grown over a large range of thermal conditions. Although the three clusters provide a good agreement with the current growth conditions, a strong warming trend is projected in the future, resulting in projections of a northward shift and move to higher elevations for the cluster patterns. Hence, other European regions may experience improved growing conditions for the settlement of these Portuguese varieties. Nonetheless, future varietal selection will heavily depend on the interest of winemakers and global market policies for the production of specific wines. Adaptation measures may indeed be required for maintaining the current varietal distribution.