Ecosystem heterogeneity is key to limiting the increasing climate-driven risks to European forests

Science for societyForest mortality due to natural disturbances such as fires, storms, and pests has increased in Europe in recent decades and is expected to increase further due to climate change. Although important forest services may soon be seriously affected, assessments of the negative effects of natural disturbances and possible solutions to minimize them are still scarce. Ecosystem heterogeneity—the diversity of tree species and sizes—has been suggested as an option to increase forest resistance, but its effectiveness remains elusive. Here, we estimate the biomass loss due to natural disturbances on European forests from 1979 to 2018 and evaluate the benefits of increasing forest heterogeneity. We used the Intergovernmental Panel on Climate Change method for climate risk assessment by integrating disturbance records and satellite data. Results show that enhancing the ecosystem heterogeneity could reduce biomass loss by about 18%, and such action should therefore be fostered to minimize climate-related risks to European forests.Highlights•Forest disturbances have led to a rise in biomass loss in Europe over 1979–2018•Climate change has largely determined the increasing trend in risk•The contribution of insect outbreaks is prominent compared to windthrows and fires•Enhancing ecosystem heterogeneity reduces the climate risks to European forestsSummaryThe rise in forest disturbances due to climate change poses a serious threat to key forest ecosystem services, yet impact and adaptation assessments are scarce at European scale. Here, we estimate the forest biomass loss in Europe due to fires, windthrows, and insect outbreaks over 1979–2018 and evaluate potential adaptation benefits by integrating machine learning with disturbance data and satellite products. Results show an average overall annual biomass loss of 41.6 ± 5.3 Mt at European level subject to a significant rise of 2.3 ± 0.3 Mt year−1, largely influenced by climate change (72%–98%). The contribution of insect outbreaks appears prominent (79%) compared to windthrows (20%) and fires (1%) and linked to their upsurge after the year 2000. However, impacts vary greatly across Europe depending on local environmental conditions. We estimate that enhancing ecosystem heterogeneity could reduce biomass loss by about 18%, and such action should therefore be fostered in forest adaptation policies.Graphical abstract