German parks are suffering from climate stress

German parks are suffering from climate stress

Shortened treetops in Berlin’s Schönhausen Palace Park. © TU Berlin

Heat, storms and drought – the increasingly frequent extreme weather events caused by climate change are also threatening Germany’s historic green spaces, according to the first nationwide park damage report. Accordingly, the extreme weather events of recent years have caused severe damage to the old trees in many parks. The high biodiversity in the facilities also shows which tree species are best able to cope with future climate challenges. The scientists say that the results can therefore serve to preserve the culturally and ecologically important facilities.

In the wake of climate change, more frequent and more intense climatic events are to be expected: these fears of climate researchers seem to have already become reality. In recent years, people and nature in Germany have suffered particularly intensively from unusual periods of drought, heat waves and storms. It seems clear: In addition to the forests, the parks in our country were also affected by these pressures. But so far there have only been individual reports from the responsible institutions of certain parks – so far there has been a lack of comprehensive documentation. Researchers at the Technical University of Berlin have now closed this gap with the support of the German Federal Environmental Foundation: They have prepared a park damage report with reference to the year 2022 – a “state assessment of the damage to trees in historical parks in Germany as a result of climate change”.

62 parks examined

The study is based on the evaluation of data sets from 62 parks in Germany. Information about the vitality of the individual tree species, the condition of the parks as a whole and the dependence of the findings on the environmental parameters in previous years were evaluated. Satellite data from the Sentinel-2 space mission of the Copernicus program of the European Space Agency (ESA) were also included in the investigations. These involved evaluations of spectral data: certain signatures of the light reflected by plants allow conclusions to be drawn about their condition. The scientists were also able to identify development trends in some parks during periods of extreme weather.

As the team reports, the park damage report gave a poor overall picture of the health of the trees in the parks for 2022: The bottom line is that around 60 percent of all trees showed impairment, which can mainly be attributed to heat and drought in the period from 2018 to 2020. In detail, this means: Only around 41 percent of the trees were vital or only slightly weakened. Around 50 percent were mildly to moderately affected and nine percent were severely damaged or even dead. However, these average values ​​result from findings that vary widely from region to region, the scientists emphasize. Depending on the specific sensitivity of the systems and the different weather patterns at the respective locations, there were minor to very strong effects.

Parks in Liebenstein, Wiesbaden, Lichtenwalde, Jenischpark in Hamburg and Park Schönfeld in Kassel were particularly affected, with a proportion of 90 to 100 percent of damaged trees. On the other hand, there are also parks in which only five to 25 percent of the trees can be classified as damaged, the study shows. The conclusion is therefore: “Overall, we have noticed an overall deterioration in the situation with the trees in recent years. However, the effects varied greatly locally. “This shows again that we have to take climate change seriously, but we should be careful not to generalize and expect the same problems everywhere,” says study leader Norbert Kühn from the Technical University of Berlin.

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As the researchers further report, the study also provided results that could benefit the adaptation of the parks to the expected climatic conditions. It showed which tree species in the parks coped better or worse with the stress. “It is now important to rethink the future design of parks. What is needed are more tree species that can tolerate heat stress and drought,” says Kühn. Certain species stand out in the results: “For example, the so-called ‘nearly natives’ – i.e. species that come from areas adjacent to the south and would sooner or later immigrate to us anyway as a result of climate change,” says Kühn. According to him, examples are the downy and distorted oak, the flowering ash, hop beech and the silver linden tree. They could apparently be “tree species of the future” that could also make park plantings more resilient overall.

The protection of historical parks has a complex meaning, Kühn concludes. Because they are not only cultural assets and recreational areas, but also have a positive influence on the urban climate and also have biological relevance. The study also made this clear again: the scientists documented a total of 543 different tree species in the 62 systems examined. “Some of the parks have been lovingly cared for over centuries and in some cases communities have been preserved in them that have become extinct in the surrounding, intensified landscape. It should therefore be a social task to preserve it for all of us even in times of climate change,” said Kühn. That’s why you should continue to keep an eye on the development of the condition of the parks, concludes Alexander Bonde from the German Federal Environmental Foundation: “Ideally, a regular analysis will be developed from the current work – analogous to the forest condition report,” says Bonde.

Sources: Technical University Berlin, German Federal Foundation Environment

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