The impact of climate change on urban trees

Climate change poses a significant threat to our urban trees. Rising average temperatures, prolonged dryness and droughts as well as new pests endanger the health and survival of many Tree species in German cities. This article examines which trees are particularly affected and what measures can be taken to increase the resilience of urban trees.

The effects and consequences of climate change on urban trees are diverse and profound. The rising temperatures lead to drought stress, increase water requirements and disrupt the photosynthesis processes of the trees. This is even more problematic in densely built-up cities, as the asphalt and concrete store additional heat and warmth. One example of this is maple trees in Munich, which have been increasingly suffering and weakened by the heat in recent years. This urban heat island phenomenon makes it more difficult for urban trees to cool down and often leads to tree damage and requires more water resources.

In addition to rising temperatures, increasingly long periods of drought are another challenge. In Berlin, beech trees in particular have been exposed to drought in recent years. They need constant human irrigation to survive. Nevertheless, the number of beech trees has declined considerably in recent years.

Pest infestation and tree diseases are also an ever-growing problem. Milder winters encourage the spread of pests such as the ash beetle. In Hamburg, for example, ash trees are frequently infested by the ash beetle, which has significantly reduced the tree population and caused damage to many ash trees.

Particularly endangered tree species in German cities

Some of the most vulnerable tree species in Germany include the Norway maple (Acer platanoides), the European beech (Fagus sylvatica), the European ash (Fraxinus excelsior) and the silver birch (Betula pendula). These species are particularly susceptible to heat and drought stress as well as pests and diseases that are becoming more prevalent and spreading more quickly due to climate change.

• Norway maple (Acer platanoides): The Norway maple tree suffers particularly from heat and drought. Especially in urban regions like Munich, Norway maples have the problem of getting enough water. They often show signs of drought stress, such as wilted leaves or premature leaf shedding.
• European beech (Fagus sylvatica): The common beech is one of the most important and widespread tree species in Germany and is particularly sensitive to drought. In Berlin, a particularly large number of beech trees have died or been damaged by the drought of recent years. The bark often cracks and makes the beech more susceptible to fungal infections.
• Common Ash (Fraxinus excelsior): The ash tree is primarily threatened by the ash jewel beetle. The mild and warmer winters of recent years have made it easier for this pest to spread. In Hamburg, a significant portion of the ash population has already died due to the damage caused by this beetle.
• Silver birch (Betula pendula): This birch is sensitive to fluctuating temperatures, extreme weather events and prolonged drought. In urban regions such as Leipzig, many weeping birch trees have already died due to extreme weather events caused by heat waves and water shortages.

Mitigation and adaptation strategies

The health and resilience of urban trees can be improved through various measures. One of these strategies is to reforest cities with drought-resistant tree species, such as the black locust (Robinia pseudoacacia) and the ginkgo (Ginkgo biloba), which can better cope with drought and climate change.

Efficient irrigation systems are extremely important here. Tree irrigation bags have proven to be particularly useful. These water bags release water into the soil over many hours through drip irrigation and seep deep into the ground, reaching the tree's root system without water evaporating or running off the surface. They are primarily used in the dry season. The bags can be easily placed around the tree trunk like a jacket, enabling resource-saving and effective tree irrigation.

Another point is ecological urban planning, which promotes tree health. The creation of so-called "green" corridors and the avoidance of heat islands can have a positive effect on the urban microclimate. One example is the "Green Lung" project in Leipzig, in which large green areas were created that reduce the inner-city temperature and improve air quality.

Civic engagement is just as important, if not crucial. Tree sponsorships, which are offered by cities and municipalities, but also by private initiatives or non-profit organizations, help to motivate and involve citizens in caring for and watering city trees. This strengthens community action.

A stronger collective initiative is needed

The survival of urban trees also requires research and development. German science and climate research is working on solutions to develop climate-resistant tree species and promote their successful use in urban forestry. Political support at the local and national level is also essential in order to define the right legal impulses and regulations for clear implementation.

Planting trees is one thing – the path afterwards is another

Urban trees are invaluable to the urban ecosystem. They provide shade and cooling, improve air quality and support biodiversity. That is why it is so crucial to protect trees from the effects of climate change. By planting drought and climate-resistant tree species, using effective irrigation systems (such as the baumbad irrigation bags), engaging citizens through community action and integrating science and policy, we can ensure that our cities remain green and livable.