Emergent vulnerability to climate-driven disturbances in European forests

Abstract

Forest disturbance regimes are expected to intensify as Earth’s climate changes. Quantifying forest vulnerability to disturbances and understanding the underlying mechanisms is crucial to develop mitigation and adaptation strategies. However, observational evidence is largely missing at regional to continental scales. Here, we quantify the vulnerability of European forests to fires, windthrows and insect outbreaks during the period 1979–2018 by integrating machine learning with disturbance data and satellite products. We show that about 33.4 billion tonnes of forest biomass could be seriously affected by these disturbances, with higher relative losses when exposed to windthrows (40%) and fires (34%) compared to insect outbreaks (26%). The spatial pattern in vulnerability is strongly controlled by the interplay between forest characteristics and background climate. Hotspot regions for vulnerability are located at the borders of the climate envelope, in both southern and northern Europe. There is a clear trend in overall forest vulnerability that is driven by a warming-induced reduction in plant defence mechanisms to insect outbreaks, especially at high latitudes.

Biological Legacies and Rockfall: The Protective Effect of a Windthrown Forest

“…It is thus fundamental to recognize the role of biological legacies left by disturbances [15], since they can strongly influence both the post-disturbance recovery pattern [16,17] and the residual provision of ecosystem services through their type, number, and spatial arrangement. Regarding windstorms, the main disturbance affecting European forests [13,[18][19][20], the main structural legacies that are present on a windthrown site are lying logs, stumps and snags, or snapped trees. After the Vivian storm in Switzerland, it was observed that the presence of deadwood could have a positive effect in scattering the energy of falling blocks, due to an increase of terrain roughness [21].…”

Oaks as Beacons of Hope for Threatened Mixed Forests in Central Europe

“…The quick succession of abiotic and biotic stresses can further worsen forest damage. A quantification of the vulnerability of European forests to windthrows (40% of losses), fires (34%), and insect outbreaks (26%) during the period 1979-2018 revealed that about 33.4 billion tons of forest biomass were seriously affected by these disturbances (Forzieri et al, 2021). There is a clear trend toward higher overall forest vulnerability driven by a warming-induced reduction in plant defenses against insect outbreaks, especially at high latitudes.…”

Climate Analogues for Temperate European Forests to Raise Silvicultural Evidence Using Twin Regions

“…Climate models predict temperature to rise another 0.9-3.5 • C until 2100 (climate models in Table 1 for Europe). While for Northern Europe temperature will continue to rise drastically, for Southern Europe a further reduction of summer precipitation will probably have more severe consequences [1,4]. Forests react to climate change not gradually but rather suddenly in response to climatic extremes [5,6].…”