Climate change is unleashing more frequent and intense storms across the world, threatening lives, livelihoods, and ecosystems.
In Europe, millions of trees have been toppled by powerful winds, causing massive losses for the forestry sector and disrupting the vital services that forests provide, such as carbon sequestration, biodiversity, and recreation.
But not all forests are equally vulnerable to storm damage. A new study by researchers at the French National Research Institute for Agriculture, Food and Environment (INRAE) reveals that in Europe, the forests that are most resilient to storms are those with a greater diversity of tree species and dominated by slow-growing species with high wood density, like oaks.
The researchers also found that the positive effect of tree diversity on storm resistance was more pronounced under extreme climatic conditions, such as the hot-dry conditions of the Mediterranean region and the cold-wet conditions of northern Scandinavia.
These findings have important implications for forest management and conservation, as they suggest that promoting diversity and slow-growing tree species can enhance the ability of forests to withstand storms and mitigate their impacts on the environment and society.
The Benefits of Diversity
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The study, published in the journal Functional Ecology, used simulations to model how forests with different characteristics, such as tree species diversity, resist and recover from storm damage.
The researchers calibrated the model with data from 91,528 real-life forest plots in Europe, covering a wide range of climate conditions and forest compositions.
The results showed that forests with two or three tree species were on average 35% more resilient to storms than forests with only one species.
The type of trees also mattered - forestry plantations are typically made up of fast-growing tall trees such as conifers, but they are more vulnerable to high winds than slower-growing hardwood species such as oak.
The researchers explained that diversity can enhance storm resistance by several mechanisms. For instance, diverse forests can have more complex structures, with different heights, shapes, and crown densities, which can reduce the wind exposure and drag of individual trees.
Diverse forests can also have more varied root systems, which can improve soil stability and anchorage. Moreover, diverse forests can have more functional redundancy, meaning that if some species are damaged by storms, others can take over their roles and maintain the ecosystem functioning.
The study also revealed that the relationship between forest diversity and storm resistance varied along the European climatic gradient.
The researchers found that the benefits of diversity were more evident under extreme conditions, such as in hot and dry Mediterranean regions and cold and wet northern Scandinavia.
The researchers attributed this to the fact that extreme climates can impose additional stresses on trees, such as drought, frost, or pests, which can weaken their mechanical resistance and increase their susceptibility to storm damage.
In contrast, in more moderate climates, such as in central Europe, trees can be more resilient to these stresses and less dependent on diversity for storm resistance.
The researchers warned that climate change could exacerbate the vulnerability of forests to storms, especially in regions that are already facing extreme conditions.
They suggested that forest managers and policy makers should consider the effects of climate on forest diversity and storm resistance, and adapt their strategies accordingly.
Related article: Forest Management Entails More Than Planting Trees
