POTSDAM, Germany (AP) — The avenues, monuments and gardens of the park surrounding Sanssouci Palace, a vast green oasis in the heart of the German city of Potsdam and a UNESCO World Heritage site, look more magnificent than ever.
But a closer look shows that all is not well for the park’s trees, which are increasingly suffering from the effects of climate change. Signs include beech trees with sparse tops, large branches that have fallen to the ground and trunks with much of the bark peeling off.
“I’ve been watching this garden for over 30 years and I’ve seen very significant changes,” says Sven Kerschek, former head gardener of part of the park. “Since 2017 or 2018, we’ve seen a very, very significant increase in the number of trees and shrubs that are dying; and it’s not just the death, it’s the health of the trees that’s changing.”
The region experienced a particularly hot and dry summer in 2018, followed by several years without rain. The relatively wet summers of last year and this year have not compensated for their effects.
Heat and lack of rain aren’t the only problems, Kerschek says: “Climate change is more complex.” Well-watered trees growing along streams and lakes are also showing signs of stress. Constantly strong sun, lack of atmospheric moisture, storms, increased fungal infections and the spread of insect species that weren’t previously present in the area are all factors that play a role.
From 2002 to 2015, the park lost between 18 and 87 trees per year. This figure has never fallen below 100 since; it reached 315 in 2020 before falling back somewhat.
The Prussian Palace and Garden Foundation, which manages Sanssouci Park and many other sites in Berlin and the state of Brandenburg, is telling the story of trees’ fight against climate change this summer in an open-air exhibition called “Re:Generation”. At various locations in the park, visitors can see examples of problems and ideas on how to solve them.
“The exhibition will perhaps help to show that we have such problems here; that extreme examples of climate change are already visible not only where people live in river valleys and have to deal with flooding, but also in the idyllic Sanssouci Park,” says Katrin Schröder, curator of the foundation’s gardens.
Visitors are invited to see “sunburned” trees, whose bark is drying and peeling, making them vulnerable to fungi and animals. They can also see that groundwater has declined significantly in recent years, making life difficult for older trees in particular. But there are also more encouraging examples, of “survival artists” who have overcome the odds.
These trees give gardeners reason for hope. Kerschek, who helped design the exhibit, says they want to “try to continue working with the genetic material we have here in the garden.”
The oldest trees in Sanssouci Park are about 300 years old. It is hoped that the old, robust trees that have already experienced climatic fluctuations will be better prepared to adapt and that even if they do not appear particularly healthy, they will be able to pass on this ability through their seeds. One idea is to collect these seeds and grow young trees in a special nursery that reflects the harsh conditions in the park, Kerschek explains.
Sanssouci Palace was the summer residence of Prussian King Frederick II, better known as Frederick the Great. It was completed in 1747 with lavish vineyard terraces, a royal retreat whose name means “carefree” in French.
The garden was subsequently greatly expanded, becoming a 19th-century landscaped park covering nearly 300 hectares and measuring over 2 kilometres from east to west. It has nearly 60 gardeners and has been a UNESCO World Heritage Site since 1990.
Although almost all of the park’s native tree species have been impacted by the effects of climate change, the solution is not to switch to exotic species.
Schröder notes that Potsdam still has a central European climate with sometimes long and very late frosts, so “we can’t do anything here with Mediterranean vegetation.”
But one approach might be to see if varieties of lime, oak, beech or other species could be used from regions like southeastern Europe, which have very hot summers but also late frosts, she says – as long as they resemble the trees already present at Sanssouci.
“We don’t want to change the park in such a way that it has a completely different mix of trees,” says Schröder.
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AP video journalist Pietro De Cristofaro contributed to this report.
