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Climate change is fueling forest disturbances

Europe’s forests are increasingly under pressure from wind, bark beetles, and wildfires, write Rupert Seidl, Werner Rammer, Mart-Jan Schelhaas and Hans Verkerk.

Climate change is already altering the environment. Long-lived ecosystems such as forests are particularly vulnerable to the comparatively rapid changes in the climate system. A new international study published this week in Nature Climate Change shows that damage from wind, bark beetles, and wildfires has increased drastically in Europe’s forests in recent years. Disturbances like windthrow and forest fires are part of the natural dynamics of forest ecosystems, and are not, therefore, a catastrophe for the ecosystem as such. However, the recent intensification increasingly challenges the sustainable management of forest ecosystems.

Damage caused by forest disturbance has increased continuously over the last 40 years in Europe, reaching 56 million cubic meters of timber per year in the period 2002 – 2010. Scenario analyses for the coming decades also suggest a continuation of this trend: we estimate that forest disturbances will increase damage by another million cubic meters of timber every year over the next 20 years. This increase amounts to the approximate timber volume stocking on a forest area corresponding to 7000 soccer fields. Climate change is the main driver behind this increase: under assumed stable climatic conditions we find no substantial further increases in forest disturbances beyond the current levels in our simulations. Damage from forest fires was particularly estimated to increase on the Iberian Peninsula, while bark beetle damage increased most strongly in the Alps. Wind damage would be seen to rise most notably in Central and Western Europe.

There is strong feedback from forest disturbances on the climate system. Currently, Europe’s forests are mitigating climate change by taking up large quantities of the greenhouse gas carbon dioxide. The carbon loss from increasing tree mortality and disturbance could, however, reduce this uptake and reverse the positive effects of forest management aimed at reducing climate change. The climate-induced increase in forest disturbance could thus further amplify the progression of climate change. Therefore, we believe it is time that we include risk calculations in our policies and forest management planning systems, rather than accepting it as something that may happen or not, or even worse, neglecting it altogether. Adapted management strategies, such as increased biodiversity and optimised thinning interventions in Europe’s forests, can buffer these carbon losses and support the climate change mitigation function of forests. With this study we can distinguish areas with different future risk levels. In high-risk areas, it might be better to harvest trees early and use the biomass to substitute fossil fuels, rather than trying to stock as much biomass as possible in the forest and losing it in a fire or a storm. We don’t think we should forget about carbon sequestration in forests, but be realistic in the risks associated with the strategies we choose, and find ways to mitigate those risks. Europe’s forest management will thus need to adapt to changing disturbances in order to keep sustaining the diverse set of ecosystem services provided to society in the future.

Rupert Seidl and Werner Rammer work for BOKU Vienna, Mart-Jan Schelhaas works for Alterra, Wageningen University and Research Centre, and Hans Verkerk for the European Forest Institute

 

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