At least one-third of European trees not adapted to global warming

Climate change presents a complex challenge for forests: the number of native European species adapted now and up to 2100 will fall sharply, according to a new study.

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Climate change is set to reduce the "species pool" of trees from which foresters in Europe can draw by at least a third compared to the current pool. This is the worrying finding of work published on Monday, April 29, in the journal Nature Ecology & Evolution. At a time when the continent's forests are being hit hard by fires, droughts and diseases, largely linked to global warming, the number of European species available to adapt forests to these upheavals already appears particularly limited.

Ash, oak, willow, alder, pine... For this study, researchers took into account the distribution of 69 species native to Europe, i.e. over 90% of European species - the continent has few endemic species compared with other regions of the world - as well as occurrence datasets from over 238,000 forest plots. They then modeled the resilience of trees up to 2100, according to three climate scenarios. The first scenario predicts a warming of around 1.6°C by 2100 compared with the period 1850-1900, the second a warming of 2.5°C, and the third around 4.3°C.

On average, according to their results, the number of species per square kilometer able to survive the century would decrease by around 33% compared to the current number of species, in the least severe scenario. Species would decrease by 38% in an intermediate scenario (nine species could be planted per square kilometer) and by 49% if warming were even more severe. The impact differs according to geographical zone: Northern and Western Europe are likely to be more affected than the center and east of the continent. Mountain regions would also be relatively spared.

'Bottleneck'

While other research has already described the evolution of the ranges of different tree species, this new publication shows that the climate crisis could create a kind of "bottleneck" in forest management: species adapted to a particular region today may no longer adapt to the future climate.

While new species will be able to establish themselves in a given location as warming increases, they cannot do so now, for example because cold periods continue to occur. However, forest managers can only use climatically viable species both now and in the future.

"In general, we use modeling to look at where species are located and where they may be in the future, and this allows us to say whether the range will expand or shrink," explained Johannes Wessely, lead author of the study and researcher at the University of Vienna in Austria. "But for species that live for a very long time, the story is different: when a forester plants a tree to exploit its timber, that tree will have to survive in the same place for 80 or 100 years."

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