The Swiss forest is under increasing stress


In Switzerland there is often dry heat in summer, which increases the evaporation of the trees in the air. If they don’t get enough water from the ground, they can no longer cool down and are damaged. Weakened trees are more sensitive to external influences such as storms or pests.

“We had massive bark beetle damage this year and last year,” says Gessler. For example, he expects spruce mortality to increase, which the beetles prefer to infest. Hot summers and warm winters do their part. Beeches are also at risk in certain locations and there will be more and more such locations due to climate change. In addition, according to Gessler, the death of the pine will increase in the long term, especially in lower locations such as the Rhone Valley in Valais.

“If we experience a hot summer again, there will be great damage.”

Arthur Gessler, ecologist

It is often observed that the actual mortality only becomes visible in the first and second following year. And the last three summers were all events of the century (here is our evaluation:
156 Swiss summer in comparison). The effects of this are likely to be felt this year. For example, due to the reduction in water content, many beech forests turned brown and are still badly damaged today.

If it remains dry this year, the situation would worsen. “If we experience a hot summer again, there will be great damage,” warns Gessler and refers to the previous forecasts with concern. The
World Weather Organization (WMO) expects a “record heat season” in the northern hemisphere in 2020. It has not yet arrived in Switzerland. But that was also the case in 2018, which in the end broke numerous records as a hot and dry year. The seasonal outlook from
Meteo Switzerland, i.e. the forecast of the temperature trend for the next three months, gives an idea that we are again announcing an above-average warm summer.

The Swiss forest is generally still in good condition and has even increased in terms of biodiversity in recent years. But it is coming under pressure due to climate change: this is also the conclusion of the latest federal government Forest report. Accordingly, periods with a high risk of forest fires have lengthened. Due to the warming up, the supply of wood to conifers such as the spruce in the lowlands is declining. And the risk of heat-loving pests spreading in the Swiss forest is increasing.

What can you do about this development? According to Gessler, mixed forests should be promoted, as is already being done in Switzerland. “This has the effect that different trees support each other, for example if their roots reach different depths and they do not take water from each other,” explains the WSL researcher.

Another opportunity is to promote tree species that suffer less than others during the dry spells. The oak such a candidate. Introduced tree species such as the Douglas fir, the great coastal fir or the oriental beech could also be of use. But the question of which tree species will survive in a warmer and drier climate in the future and which will produce a sufficiently large yield from the timber industry remains open, the authors of the forest report write.


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