Significant increase in forest disturbances since 1950s

Natural disturbances are important drivers of forest ecosystem change. Canopy openings caused by disturbances promote tree regeneration and increase species diversity. However, disturbances can also cause ecosystem degradation, widespread tree mortality and damage large amounts of wood, potentially transforming forests from sinks to net carbon sources.

Large-scale disturbance increases may:

• counteract the implementation of improved and climate-smart forest management to mitigate climate change, hampering the achievement of EU climate targets;
• strongly disrupt long-term forest planning in disturbance hotspot regions, making it difficult to ensure sustainable harvesting and ecosystem services provisioning, and heavily affecting local economies, human wellbeing and safety.

Key trends explained

• Wind disturbances caused 46% of total timber volume damage. The majority were extreme windstorms (peaks), supplemented by widespread chronic damage with particularly high rates in the 1990s and 2000s.
• Forest fires were responsible for 24% of total timber volume damage. In the 1970s and 1980s, there was a significant increase in fire disturbance, followed by two opposing trends. Smaller and average-sized fires have decreased since the late 1990s as a result of improved fire management, detection and control, but climate change related mega-fires increased. Most recent research predicts that fire size and severity will increase across all European biomes under future climate conditions.
• Almost 20% of damage was caused by bark beetle calamities with a dramatic increasing trend in the last decade. The years 2020 and 2021, which had even greater damage, were excluded.
• Pests and diseases (other biotic damages) accounted for 8% of total timber damage with the strongest positive trend and a sharp increase after the 1980s, most likely influenced by climate change.
• Other abiotic disturbances (e.g. due to snow and ice) increased, with certain years (e.g.2007) exhibiting high damage peaks.

Incomplete reporting on forest disturbances

Reporting practices vary greatly between countries. Data analysis revealed that consistent data collection on disturbance events is lacking, particularly for the reporting of smaller, dispersed damage. Moreover, other biotic disturbances (with greatest damage increase) are among the most widely underreported disturbance agents.

Reference

Patacca, M., Lindner, M., Nabuurs, G.-J. and Schelhaas, M.-J. 2023. Significant increase in forest disturbances since 1950s. Policy Brief 4. European Forest Institute. https://doi.org/10.36333/pb4

Further reading:

Patacca, M., Lindner, M., Lucas-Borja, M.E., Cordonnier, T., Fidej, G., Gardiner, B., Hauf, Y., Jasinevičius, G., Labonne, S., Linkevičius, E., Mahnken, M., Milanovic, S., Nabuurs, G.-J., Nagel, T.A., Nikinmaa, L., Panyatov, M., Bercak, R., Seidl, R., Sever, M.Z.O., Socha, J., Thom, D., Vuletic, D., Zudin, S., Schelhaas, M.-J. (2023). Significant increase in natural disturbance impacts on European forests since 1950. Global Change Biology, 29(5):1359-1376.  https://doi.org/10.1111/gcb.16531

Grünig, M., Seidl, R., Senf, C. (2023). Increasing aridity causes larger and more severe forest fires across Europe. Global Change Biology. https://doi.org/10.1111/gcb.16547