Wind damage can trigger years of forest vulnerability

Windstorms are among the most important natural disturbances in Northern Europe, causing extensive tree mortality, timber losses and long-lasting changes in forest structure. Large-scale windstorm damage has increased across Central and Northern European forests in recent decades, while in boreal regions such as Finland, warmer winters and shorter periods of frozen soil may further reduce tree stability and increase vulnerability to wind.

The consequences of wind damage, however, can continue long after the storm has passed. A large-scale study of more than 70,000 wind-damaged forest stands across Finland found that forests affected by wind may remain vulnerable to subsequent bark beetle or snow damage in the years that follow. These disturbance pathways depend on forest structure, climate, topography and tree-species composition.

“Forest disturbances are often considered separately, but in fact, one disturbance can change the conditions under which the next one occurs,” says Doctoral Researcher Qianqian Tian, lead author of the study at the University of Eastern Finland. “We wanted to understand what happens after wind damage and whether forests subsequently affected by bark beetle or snow damage share the same characteristics.”

Forest structure played an important role in shaping what happened after wind damage. Warmer conditions and forest composition helped distinguish stands subsequently affected by bark beetles from those affected by snow, while mixed stands showed a greater tendency towards bark beetle rather than snow damage when compared with pine-dominated stands. These differences suggest that post-storm vulnerability depends not only on the initial disturbance, but also on the structural and environmental conditions of the affected forest.

“This has important practical implications, since it can help us adapt monitoring and forest management after a storm to reduce future losses,” says Professor Blas Mola-Yudego, coordinator of the study at the University of Eastern Finland. “After a storm, a dense and structurally heterogeneous forest in southern Finland may require different attention than a pine-dominated stand in North Karelia. Forest risk management should consider what may happen next, rather than focusing only on the damage that has already occurred.”

The timing of subsequent disturbances was also notable. Around 94% of wind–snow damage sequences and 76% of wind–bark beetle sequences occurred within five years of the initial wind disturbance, while more than 90% of both types of sequences occurred within eight years.

“The years immediately following a major wind disturbance can therefore be particularly important for monitoring and preventing further damage, but our results also show that we should not look for the same warning signs everywhere,” says Marina Peris-Llopis, co-author of the study.

Mari Selkimäki, lecturer in forest planning at the University of Eastern Finland, highlights the importance of the large-scale forest information used in the research: “Combining national forest data with long-term damage records allowed us to look beyond individual storms and identify broader patterns in how disturbances interact across boreal forests.”

More than 70,000 observations openly available for further research

An important outcome of the study is that the processed dataset underlying the analysis has been made openly available for reuse and further modelling. The dataset contains information for more than 70,000 wind-damaged forest stands across Finland, combining variables describing forest structure and species composition with climate, topography and subsequent bark beetle and snow damage.

The dataset can therefore be used beyond the analyses presented in the paper, for example to test alternative statistical or machine-learning approaches, investigate disturbance interactions, develop risk models, or compare post-disturbance dynamics with other forest regions.

➡️ Open dataset: https://doi.org/10.5281/zenodo.21060824

The results support more targeted monitoring after storms. Structurally heterogeneous forests containing spruce, particularly in warmer areas, may deserve greater attention for subsequent bark beetle damage, whereas forests on steeper terrain may require closer monitoring for snow damage. Maintaining stand stability and avoiding excessive stand density may also help reduce vulnerability to interacting disturbances.

➡️ Read the paper: Tian, Q., Peris-Llopis, M., Selkimäki, M., & Mola-Yudego, B. (2026). Post-wind vulnerability of boreal forests: Structural and site drivers of sequential snow and bark beetle disturbances. Forest Ecology and Management, 619, 124074.

Spatial distribution of forest damage records and sequential disturbance pathways in Finland. Panel (a) shows the distribution of individual wind, snow, and bark beetle damage polygons. Panel (b) shows locations where wind damage was followed by bark beetle damage, and panel (c) shows locations where wind damage was followed by snow damage in a subsequent year. Panel (a) is displayed as polygons, whereas in panels (b) and (c), points represent the locations of sequential disturbance records included in the analysis.

These findings are part of a broader pan-European research effort aimed at developing more resilient forests and supporting climate-change adaptation across Europe, funded by the European Union's Horizon Europe Programme through the Eco2Adapt project and by the Strategic Research Council of Finland through the ForTran project.