The Swiss forests of the future
(MENAFN-Swissinfo) Forests cover almost a third of Switzerland. By planting new species, they aim to withstand the threats of climate change and drought. keystone
Switzerland is planting exotic species from drier climate regions to see how they adapt to the warmer temperatures that come with climate change. We took a look on site at what the forests of the future will look like.
This content was published on May 30, 2022 – 09:00 May 30, 2022 – 09:00
As a Ticino journalist living in Bern, I write reports, articles, interviews and analyzes on scientific and social topics. I am interested in environmental, climate change and energy issues as well as migration, development aid and human rights in general.
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- English (de) Switzerland is experimenting with the forest of the future
- 中文 (zh) 瑞士试验外来树种,构建未来森林
- Français (fr) La Suisse is experimenting with the Forêt du futur
- Italiano (it) La Svizzera sperimenta la foresta del futuro (Original)
Peter Brang walks slowly through the beech forest. It’s been over a year since he was last here and it’s not easy to navigate the undergrowth of the forest on this warm spring day. He’s looking for a wire mesh attached to wooden stakes: a fence he erected to mark his outdoor lab. “Here we are,” says the expert in forest dynamics after a few minutes’ walk.
Within the marked area, the towering larches that once populated the area have been felled. Only a few isolated tree stumps remain. Instead, Lebanese cedars (Cedrus libani), an evergreen conifer native to the Middle East, were planted. Some of the trees are three meters high, others are only up to our knees. One has died.
We are in Mutrux, a small commune in the canton of Vaud in western Switzerland. Six exotic tree species from Turkey, Bulgaria and the United States were planted here in 2012 on a plot of around three hectares. It is an example of what is known as “assisted migration”. lasted at least millennia,” explains Brang, a researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). There is nothing unusual about his experiment. Humans, he adds, have been intervening to shape forests to suit their needs for centuries.
The introduced species were chosen for their high resilience to drought and heat waves. Brang wants to study their growth and survivability in this new environment. “We want to know which trees could replace the species that are important for Switzerland and are suffering from climate change,” he says.
Global warming is leading to more frequent and intense summer droughts and hot spells, and is stressing native tree species that have evolved in more temperate climates. The forest will not disappear, but there is a risk that it will no longer be able to provide vital services such as protection against natural hazards or wood production, says Brang.
Robert Jenni, research associate at the Federal Office for the Environment, who is accompanying us on the visit, clarifies that Switzerland’s strategy is not to replace native species, but to enrich the forest with exotic species. “The forest is a very resilient ecosystem. We want to give as many opportunities as possible to those species that already grow naturally and have some adaptability,” he says.
50 years to study the species of the future
As part of another external link project, WSL and the Federal Office for the Environment are building a network of 57 experimental plantations across Switzerland. The aim is to investigate the climate compatibility of 18 tree species over a period of 30-50 years.
These include native species such as silver fir and larch as well as species from warmer regions such as Constantinople hazel and Douglas fir, which are intended to guarantee the productivity of the Swiss forest. A total of 55,000 seedlings will be planted. First results are expected in 2025.
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A Turkish fir tree for Christmas?
We are moving to an area where Turkish firs (Abies bornmuelleriana) have been planted. This conifer from the mountains of northern Turkey tolerates long periods of drought and temperatures down to -18 degrees Celsius, making it an ideal replacement for the Swiss Norway fir or spruce. “Maybe one day we’ll find him as a Christmas tree,” says Brang.
He explains that the species introduced in MutruxExternal link have been selected based on ecological criteria and their economic value. They come from regions with climatic conditions that will also prevail in Switzerland in the future. The alien species pose no threat to the native species and have so far been resistant to pathogens, Brang said.
The “luck” of the 2018 drought
The Mutrux experiment is part of an international project coordinated by the Bavarian State Forestry Agency in Germany. As part of this long-term experiment, the same exotic species from the same location were planted at five locations in Germany, Switzerland and Austria. “There are not many such experiments internationally. Normally you test different provenances of a species,” says Brang.
A network of test sites makes it more likely that scientists will see extreme events at at least one of them. Of particular interest to the researchers are long-lasting droughts and heat waves. In this sense, the exceptionally hot, rain-free summer of 2018 was “a stroke of luck,” says Brang die Arten.
The summer of 2018 hit several European countries and in Switzerland it was the third warmest since statistics began in 1864. The high temperatures reached 34 °C between late July and mid-August, causing around 200 more heat-related deaths during this period than in this period a normal year. Water was scarce in many areas of the Alps and the army had to use helicopters to secure water supplies. The drought caused heavy losses of grass and forage crops and lowered the level of the Rhine for an unusually long period, disrupting the movement of goods on the river.
It also affected the forests and large trees, especially the varieties of white spruce and beech. In 10% of central European forests, trees prematurely lost some or all their leaves, according to a WSL analysisExternal link. Eastern Central Germany and the Czech Republic were hardest hit. In the Swiss mountains, where it was less hot and dry, the forest damage was somewhat less. But if such droughts return, the analysis shows that beeches and firs may not survive in the long term.
External Content Spruce s suffer the most
Intense and repeated droughts are drying out soils and increasing the annual mortality rate of all major European tree species by up to 60%, according to a major international studyExternal link not yet peer-reviewed.
Without water, trees are more susceptible to pests and diseases. The risk of forest fires is increasing and the forest can no longer fulfill its essential functions, which include protecting people from avalanches, landslides and floods, especially in mountainous areas. For the next few decades, Brang predicts that there will be ever larger areas in which these conditions can no longer be guaranteed, at least temporarily. “That worries me,” he says.
Spruces, the most common trees in Switzerland, are particularly at risk. They have shallow roots that prevent them from foraging deep for water during summer droughts. The trees are less resistant to bark beetles, which prevent sap flow under the bark.
The timber industry is looking for alternatives
With the decline in spruce, forestry is threatened with the loss of one of the most sought-after tree species. Conifers provide two-thirds of the wood used for construction, furniture, and power generation.
In 2020, the Swiss forest delivered 4.8 million cubic meters of wood. For comparison: The Swedish furniture group Ikea used around 21 million cubic meters of logs worldwide in 2019.
External Content
Thomas Lädrach, President of the umbrella organization of the Swiss wood industry (Holzindustrie Schweiz), says that the industry will continue to use softwood, as hardwoods can only be used to a limited extent as a building material. Alternatives to native spruces are therefore in demand.
These include Douglas firs, which grow in the western coastal regions of North America. The coniferous tree, up to 57 meters high, tolerates the summer heat well and is more resistant to drought than spruce and fir. It is not yet widespread in Switzerland, but has proven to be robust as it has rarely been attacked by bark beetles. Brang says Douglas firs could eventually make up 10% of Switzerland’s forest in the future if they survive local conditions.
Cedar forests in Switzerland?
Then there is the Lebanese cedar, one of the species that Brang grows at the Mutrux trial plot. The strength of its wood is similar if not greater than the commercial trees found in Swiss forests. According to the trade magazine BaublattExternal link, it is a good candidate to replace spruce and Scots pine in construction.
But it’s still too early to predict how well the species will acclimate and grow in Switzerland. A first evaluationExternal link took place in 2018, six years after the start of the project. A high mortality rate was observed for some species at all sites in Switzerland, Germany and Austria. Three out of four cedars whose seedlings came from a Bavarian nursery did not survive. “Apparently, the species is very sensitive to drying out when transplanted,” says Brang. “We didn’t know that.”
The seedlings planted in a second phase grew slowly and remained small. They may have lost three to five years in their growth, Brang says, but that’s negligible when a tree lives for hundreds of years. Most notably, they do not appear to have suffered excessively from the 2018 drought. “So far, there is nothing to indicate that the species introduced here are not suitable for cultivation in our latitudes,” says Brang.
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Above all, Brang doesn’t want to experience another nasty surprise like he and other forest observers experienced with the black pine. Thirty years after its successful planting in Switzerland, fungi attacked its leaves and the species is now in decline. “That’s why it’s important not to jump to conclusions,” he says. “Only in 50 or 100 years will we know whether the trees we have planted today are really resilient.”
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