How Climate Change Could Affect Drought Risk in Portugal’s Traditional and Super-Intensive Olive Orchards

Portugal, a leading producer of olive oil, boasts six Protected Designation of Origin (PDO) regions, each characterised by distinct olive orchard (OR) densities, ranging from traditional to super-intensive. Although the analysis of drought and aridity conditions has been widely addressed, the impacts of these factors have not been analysed in relation to OR densities. To address this gap, a new metric, the Olive Drought and Aridity Risk Index (ODAR), was developed to assess future risk levels for each OR by quantifying the combined effects of climate and soil water availability, weighted by OR density. To achieve this, drought and aridity indicators were analysed for both a historical baseline (ERA5: 1981–2000) and two future periods (2041–2060 and 2081–2100) under two anthropogenic forcing scenarios (RCP4.5 and RCP8.5). A seven-member ensemble of global climate models was employed for the projections to address inter-model variability and reduce single-model uncertainties. From Spearman’s correlation analysis, Annual Mean Aridity (AIA) was identified as the most representative indicator of climatic exposure for OR. Readily Available Soil Water (RAW, in mm) was used to represent the soil’s water-holding capacity available to olive trees. ODAR was calculated as the Euclidean distance between each future scenario/period and the historical period, using the weighted AIA and RAW indices according to OR densities. Future projections indicate that central and northern PDOs will be characterised by intermediate conditions (AIA ≈ 0.60 and RAW > 90 mm), exhibiting variable risk levels ranging from low to high. In the southern PDO, where AIA is projected to reach 0.69 and RAW is expected to fall below 60 mm, the risk will be very high, potentially jeopardising olive tree growth, fruit development, and olive oil quality. These findings underscore the need for targeted adaptation strategies to strengthen the climate resilience of olive production in Portugal’s PDO regions.