by Wolfgang Flüs
City trees contribute significantly to the well-being of the citizens in cities. They shape the idyllic appearance of the cities and invite you to relax. But our city trees play a much bigger role because they ensure the good climate in cities. But how good will our urban climate be in the future if the ever-advancing climate change prevents urban trees from functioning?
What role do city trees play in our urban climate?
The role of city trees is very diverse. On the one hand, they regulate the temperature in the city by providing shade. This means that houses, facades and streets do not heat up too much. Measurements indicate that the road asphalt can heat up to over 60 degrees in the summer midday sun. In the shade of the trees, however, only about 30 degrees were measured.
This is why city trees are increasingly important for our quality of life and health, especially in times of climate change with increasing heat stress. The shading creates and binds moisture, which causes the air to cool through evaporation.
City trees also produce oxygen and filter CO2 and other pollutants from the city air. This process is especially important in cities because of the car exhaust. Trees in the city also provide noise and wind protection and serve as water reservoirs when it rains.
The general quality of life in cities is also increasing thanks to green spaces and proximity to parks.
How endangered are urban trees due to their location-related disadvantages?
The big problem with urban trees is the lack of space - in contrast to free-standing trees. In the city, most of the floor space is sealed by various floor coverings. In addition, there are many pipes laid underground, which is why the roots of city trees have to be distributed completely differently. Due to this limited space, the trees form smaller roots and are therefore less able to absorb water. The soil around the trees is also often highly compressed in cities, which makes it even more difficult for the soil to absorb water.
Even if the water seeps through the ground, there is not enough soil in the cities for the water to accumulate. This makes it extremely difficult for the trees to absorb water. Sometimes the water does not even reach the roots.
Another disadvantage for city trees is the buildings. If a tree is right next to a house facade, it automatically grows a little more into the street space. This often creates an overweight in one direction, which means that the tree does not have enough support in a storm and can tip over quickly.
The pollutants in the air, partially polluted soil, the use of salt in winter or injuries from construction work and accidents also endanger our urban trees.
How threatened are urban trees due to climate change?
Since urban trees are already disadvantaged due to their location, they are even more affected by climate change. The dry periods are getting longer and longer, which means great stress for the city trees, as they are already difficult to supply with water.
In addition to the dry periods, there is heavy rain instead of normal rain showers. The water masses flow off over a large area above ground and usually seep into the ground so quickly that the roots cannot absorb the water at all. The increasingly frequent weather extremes such as storms also endanger city trees and can bend or uproot them. This in turn means a great danger for residents, buildings, roads and causes economic losses.
Persistent dry periods also increase the susceptibility to pests or diseases, which shortens the lifespan of urban trees. Because of the warm temperatures, pests can spread much better.
You can find out more about the effects of climate change on urban trees in this detailed report: What does climate change mean for our urban trees
Do you want to become a tree saver by simply watering?
We have made it a matter of our hearts to protect endangered trees. Would you like to help save our city trees too? Then pouring of any kind is an enormous help. It doesn't matter whether you use a watering can, a garden hose or a water bucket: you are always a watering hero!
It is even better if you give the trees a tree bath. You can do this with the help of watering bags that release water drop by drop onto the trees. This gives the roots enough time to absorb the water. And you know what? In cities, trees are often rooted together. With just one watering bag, you can even help several trees in the best case.