The impact of climate change and weather extremes on chestnut and olive crops in Portugal.

Climate change poses a significant risk to agroecosystems, particularly for perennial fruit trees such as chestnut and olive, by affecting phenological processes, physiological stress, and interactions with pests, diseases, and environmental factors. Although previous research has examined the effects of climate change on crop productivity and plant health, important gaps remain in understanding how long-term climate trends and extreme weather events influence yields across different phenological stages. This study evaluates the effects of climatic variability and extremes on the productivity of chestnut and olive trees in Portugal over a 39-year period. Results show that the timing and intensity of climatic events relative to key phenological phases strongly influence productivity patterns in both species. Excessive rainfall during the fruit-ripening stage was associated with reduced chestnut yields, while excess soil moisture during ripening negatively affected olive production in northern Portugal. In contrast, higher average temperatures, particularly during ripening, were linked to increased olive productivity in southern Portugal. Overall, climate impacts were highly stage-specific and differed between species, with significant interannual legacy effects also contributing to productivity variability. These findings highlight the importance of incorporating phenological timing and lagged responses into crop-climate analyses to improve modelling accuracy and support the development of effective adaptation strategies for Mediterranean agroecosystems.