Natural disturbances are part of forests’ life cycles. However, in recent decades, forest disturbances have increased significantly across Europe. An international team of scientists have now also projected the area of forest in Europe that could be affected by fires, storms and bark beetle outbreaks by 2100.
Marco Patacca is a forest disturbance expert at Wageningen University & Research. He co-authored the study, which was led by the Technical University of Munich and was recently published in Science. “We combined several methods,” says Patacca. “These included satellite observations, model simulations, and climate scenarios in an AI-based forest model. Our estimations are that in 2100 all types of natural disturbances will affect larger areas of European forests than today, under all climate scenarios. In the worst-case scenario, with global warming reaching +4⁰C, the area affected by fire, storms and bark beetles could more than double.”
Rise of natural disturbances already seen
Tree mortality is not bad in itself. It is a key process in the dynamics of a forest ecosystem. Old trees die, allowing space, nutrients and light for new forest to establish. The dead trees create habitats that harbour biodiversity, while dead wood gets decomposed and renders carbon and other nutrients to the soil, ensuring that biogeochemical cycles continue.
European forests, however, already experienced a clear rise in natural disturbances over the past few decades. “Due to past management practices many forests have become more homogeneous, with fewer species and simpler structure,” explains Patacca. “This, together with the effects of climate-change, causes natural disturbances in forests to happen more often and become more intense. The forest area affected has also become larger, which changes the way ecosystems function and the benefits forests provide to society - such as carbon storage, water regulation or wood production.”
Climate-induced fire increase
Future disturbances will especially affect South and West-European forests, and the strongest increase is expected to be caused by fire. Another recently published study, part of Patacca’s PhD research, focused on the impact of future fire patterns on forest mortality. The highest area burned is estimated to be in the Mediterranean region. However, in temperate forests, given the larger standing biomass, a relative increase in burned area will cause higher levels of tree mortality, compared to the other biomes.
Opportunities to adapt
However, there is still hope for European forests to adapt to future climate. Gert-Jan Nabuurs, European Forest Resources Professor, reflects on needs and opportunities that increasing disturbances bring along: “Disturbances also shape the future of Europe’s forests. Larger calamities already make forest owners realise that their management and choice of tree species need to change. Many of them revert to other types of forests. In this way, disturbances also help to speed up the process of nature restoration.”