Olive production in the 21st century will be threatened by water stress and declining solar activity

The production of olive oil, a cornerstone of Mediterranean diet, faces important threats from recurring droughts and the anticipated decline in cyclical solar activity. These escalating challenges cast uncertainty on the long-term sustainability of olive-growing regions. Here we draw on 8000 years of olive pollen data - closely related to flowering, fertilization and fruit production - to identify the key long-term determinants influencing olive yields. Our findings indicate that pollen production, and therefore yields, are primarily driven by photosynthesis, which is influenced not only by temperature and CO₂ levels, but also by precipitation during olive phenological stages and changes in the radiation balance, rather than by variations in solar energy alone. Changes in photosynthetic activity emerge as a critical determinant of the future of the Mediterranean olive oil economy and have major implications for food security in the region.