A study reveals that rising summer temperatures are causing a breakdown in masting, a reproductive strategy in European beech (Fagus sylvatica) that involves synchronized seed production to enhance pollination and reduce seed predation. The research, based on 50 long-term datasets across the species' range, shows that increasing summer temperatures are reducing the interannual variability and synchrony of seed production, leading to lower viable seed output. This masting breakdown is linked to warming local temperatures, not just average conditions, and is observed across the pan-European distribution of beech. The study highlights that while overall seed production may increase, the variability in seed production has decreased, which could reduce the viability of seed crops. This change may affect forest resilience and community dynamics, as masting plays a key role in regulating seed predator populations and pollination efficiency. The findings suggest that climate change is altering the reproductive patterns of beech, with potential consequences for forest ecosystems and wildlife. The study underscores the need for further research to understand the broader implications of masting breakdown on forest functioning and biodiversity.A study reveals that rising summer temperatures are causing a breakdown in masting, a reproductive strategy in European beech (Fagus sylvatica) that involves synchronized seed production to enhance pollination and reduce seed predation. The research, based on 50 long-term datasets across the species' range, shows that increasing summer temperatures are reducing the interannual variability and synchrony of seed production, leading to lower viable seed output. This masting breakdown is linked to warming local temperatures, not just average conditions, and is observed across the pan-European distribution of beech. The study highlights that while overall seed production may increase, the variability in seed production has decreased, which could reduce the viability of seed crops. This change may affect forest resilience and community dynamics, as masting plays a key role in regulating seed predator populations and pollination efficiency. The findings suggest that climate change is altering the reproductive patterns of beech, with potential consequences for forest ecosystems and wildlife. The study underscores the need for further research to understand the broader implications of masting breakdown on forest functioning and biodiversity.