Beech dieback is also spreading at the southern foot of the Jura
Published: Friday, Jul 26th 2024, 09:20
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Climate change and rising temperatures pose numerous challenges for forests. In particular, Switzerland's second most important tree species, the beech, is susceptible to drought. Beech dieback is spreading north of the Jura chain, but also at the southern foot of the Jura.
During a recent media interview in a forest above Lake Biel, the extent of the phenomenon becomes clear. All around are several mature beech trees with dry crowns and leafless branches.
Last summer, the leaves of the beech trees had already turned brown in August, reports Marion van der Meer, head of the Mittelland Forestry Department at the Bernese Office for Forests and Natural Hazards.
The rainfall in the first half of the current year has not done much to ease the situation, as the beech dieback will continue for several years.
The phenomenon is well known in the cantons north of the Jura Arc, particularly in the Jura, Schaffhausen and Basel. Beech dieback has been going on for some time. But it really hit its stride in 2018, when the summer brought Switzerland its longest and most severe period of drought since records began.
Faster and faster
It was only in the spring of 2019, when many beech trees had no leaves, that the extent of the disaster was recognized, as Mélanie Erb, Head of Forest and Natural Hazards at the Jura Environment Agency, told the Keystone-SDA news agency. The Jura government issued a disaster alert for the forest.
In Ajoie in particular, beech trees died or were severely impaired in their vitality, as Mélanie Erb explained. This dieback continues on an unprecedented scale and affects new areas in the canton every year.
The situation in the Bernese forests is not quite as critical, but the health of the beech is also a cause for concern here.
Prefer resistant tree species
The canton of Bern does not have a magic spell to stop beech dieback - but it does have a strategy. It proposes three approaches to Bern's forest owners, i.e. municipalities and private individuals, in order to contain the risks with a good mix.
The first method consists of "doing nothing". This means letting the natural dynamics of the forest run free without using the wood. The other two options aim to reduce the proportion of beech, which accounts for up to 90 percent of the trees in some forests.
For example, large trees are to be felled to bring light into the lower levels of the forest so that more resilient tree species such as oak, maple or elm can thrive there.
The third approach is to plant young trees that are more resistant to water shortages: "We don't want to eliminate beech by any means, but we also want to promote other tree species that are less sensitive to drought," notes Armin Komposch, head of forest protection in the canton of Bern.
A slow process
Couldn't the susceptibility of beech trees to drought also be seen as an opportunity to bring more diversity to beech-dominated forests? No, says Professor Charlotte Grossiord, head of the Plant Ecology Laboratory at the Swiss Federal Institute of Technology Lausanne (EPFL) and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL).
This is because young trees cannot fulfill the same functions as hundred-year-old beech trees. Replacing a mature forest is an extremely slow process that takes several decades, the scientist emphasizes.
A healthy forest with trees in various stages of life - including hundred-year-old specimens - protects against avalanches, rockfall, landslides and erosion, binds carbon dioxide, helps to preserve biodiversity and filters drinking water.
However, a forest with weakened trees is no longer able to effectively fulfill these crucial functions for humans. Wood affected by drought also loses its value as a building and fuel material.
And finally, mixed forests also suffer from heatwaves and droughts, Grossiord emphasizes. This is a phenomenon that can be observed worldwide.
©Keystone/SDA
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