Abstract
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.