The storm “Bernd” is also an opportunity for the Zurich city forest. The city forest engineer explains why on a tour.
“Bernd” raged heavily in places on the Käferberg in Zurich. City forest engineer Oliver Gerlach is standing on an uprooted tree that remains as deadwood.
In the night from July 12th to 13th, 2021, the storm “Bernd” roars over Switzerland. When it swept from the Üetliberg over the city of Zurich and the Käferberg, it was 1:45 a.m. Lightning flashed every second and thundered non-stop. Hailstones crash against facades, windows and shutters. It sounds like techno. Within a short time, the streets turn into streams. After half an hour the spook is over.
There is a rude awakening for the residents of the Zurich West and Zurich North areas. The strong fall winds of the thunderstorm cell have covered roofs, damaged facades and buried cars under branches. «Bernd» has even brought down numerous giant trees. Various parks and green areas as well as forest areas on the Käferberg and the Üetliberg have to be temporarily closed to the public for safety reasons.
This is what the forest above the Guggach area looked like a year ago.
On the morning of July 14, 2021, Käferholzstrasse near Bucheggplatz was reminiscent of a jungle.
“Bernd” costs 6 million francs
The city council has now approved CHF 6 million for the clean-up and restoration work. However, the storm damage has still not been repaired, as the city announced on Wednesday. Above all, replacing the trees will keep Grün Stadt Zürich busy for another one to two years. According to the press release, “Bernd” damaged more than 19,000 trees on roads and in parks so severely that tree care measures were necessary. Over 2000 trees fell or had to be felled.
“Bernd” also devastated the city forest. 14,000 cubic meters of wood fell victim to the summer storm. But in the aisles, the next tree generation is already in the starting blocks. Because those responsible for forests in the city of Zurich have long relied on the principle of so-called permanent forest management. In order to show on the spot what exactly this is all about, which trees can cope with climate change and what opportunities deadwood holds, Grün Stadt Zürich invited the media to a forest inspection on Wednesday.
This mighty tree could not withstand the summer storm.
Above the Guggach area the younger trees now have more light and will be able to grow faster.
When the convoy starts at Bucheggplatz, it starts to rain like cats and dogs. “After all, it’s wet again,” says Oliver Gerlach in a broad Schwyzer dialect. The 39-year-old is a Zurich city forest engineer. He states: “The drought is not yet alarming for the forest. The ground, protected by trees, has stored the spring and early summer rains.»
Above the Guggach area, the city forest engineer shows the press people an area that was densely forested a year ago, which now offers a view of the Glatt valley. In contrast to “Lothar” in 1999, “Bernd” did not cause any large-scale damage, only local damage, Gerlach notes.
Nevertheless, he was shocked when he inspected the destruction in Zurich’s city forest the day after. “It wasn’t a pretty picture. A lot of wood, a lot of leaves were lying around,” he says. But even then it was clear to him: “A storm is a natural event. The forest recovers on its own.” “Lothar” brought this knowledge to light and brought new impetus to forest management. Instead of reforesting in rows as in the past, those responsible decided to forego large-scale planting. In fact, the forests recovered on their own.
In the forest above the Guggach area, the “Bernd” thunderstorm cell, which was building up in western Switzerland at the time and reached its peak over the cities of Zurich and Winterthur, uprooted mainly mighty trees. Some have stumps left. “They will stop,” says Gerlach. The same applies to rootstocks – as long as they are safe from a safety point of view and do not suddenly start moving.
The city forest engineer describes the fact that the old trees have snapped over as an opportunity for the young trees that are sprouting everywhere. “They will now have more light and will be able to grow faster.” Without the protection of the old trees, however, the young ones would not have survived either, Gerlach notes. But growth takes time. It will take two or three decades for the young to reach the height and density of the old trees.
A young oak conquers a devastated forest.
Poles mark the places where young trees have been planted.
However, there are also larger bare areas without young wood. Grün Stadt Zürich is planting new trees here, namely those that can cope better with high temperatures and drought than others. Experience has shown that these are mainly oaks. 800 specimens were therefore planted on the Käferberg. Walnut and sweet chestnut are also among the supplementary plants. The changing climate affects them less than the maple, for example.
Biodiversity is also important, it is also part of the permanent forest management that the city of Zurich has been using for forty years. Species diversity and age mix improve the forest’s resilience to extreme events such as storms, drought or pest infestation.
Deadwood islands promote biodiversity
The bark beetle is not a problem on the Käferberg, says Gerlach. Because there are no more spruces. But he warns against ticks. They don’t bother you on the forest roads, ticks are only a danger in the thicket. It is precisely into such a thicket that Gerlach is now leading the media people. Thanks to rain jackets and long pants, nothing can happen to them.
The forest engineer presents a “deadwood island” on which Grün Stadt Zürich deliberately leaves the storm wood lying around. As it decomposes slowly, it provides nutrients for microorganisms and organisms. There are around 25 islands of dead wood in Zurich’s city forest, in less frequented places, so that biodiversity can develop as well as possible and the nutrient supply of the forest floor is strengthened.
The city forest is above all a recreational area for the city population. In order to keep him healthy, he is thinned out. The storm wood is also used. Grün Stadt Zürich sold the tree trunks as sawdust and timber. The remainder was partly processed into wood chips on site. The energy wood was used in the city hospitals of Waid and Triemli, in the zoo, in the Aubrugg combined heat and power plant and in private wood chip heating systems for the production of heat and electricity.
The Zurich forest area most affected by the storm is the Üetliberg. For topographical reasons, the timber salvage was far more demanding than on the Käferberg. Since the slopes are very steep, no machines could be used. The storm wood was transported away with cable cars and helicopters.
The storm wood is fully recyclable.
