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 like chestnut and olive, by affecting phenological processes, physiological stress, and interactions with pests, diseases, and environmental factors. Although previous research has examined how climate change affects crop productivity and plant health, significant gaps remain in understanding how gradual climate trends and extreme weather events influence crop yields at different plant phenological stages. The effects of long-term climate change and short-term weather extremes on the productivity of chestnut and olive trees, two of the Mediterranean and Portugal's most economically and culturally significant perennial crops across various regions, were examined. Results reveal 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 period was associated with reduced chestnut yields. Concurrently, excess soil moisture during ripening correlated with decreased olive production in northern Portugal. In contrast, higher average temperatures, especially during ripening, improved olive productivity in southern Portugal. Overall, these findings indicate that the impact of climate variability is highly stage-specific and varies between species, emphasising the importance of phenological timing. Results also reveal significant interannual legacy effects, part of the impacts of climate change and extreme weather events. These aspects should be considered to enhance the precision of crop modelling and to develop effective adaptation and mitigation strategies for resilient agricultural systems under future climate scenarios, especially in Mediterranean regions where chestnut and olive trees are essential to rural economies and cultural landscapes.