by Wolfgang Flüs
City trees have become an integral part of our cities. you are the green lung of the city, ensure our well-being and regulate the urban climate. Climate change is particularly affecting urban trees and increasingly preventing them from doing their important work. But why are urban trees so important and what are the devastating effects of climate change on our urban climate?
What is meant by climate change?
Climate change means the long-term cooling or warming of our global climate. We have been severely affected by global warming in recent years. As a result of this warming, our average temperatures rise continuously and even the atmosphere and oceans are warming.
Climate change is shifting climatic zones, increasing the risk of forest fires and changing the occurrence of precipitation. As a result, extreme weather such as droughts, storms, heat waves and floods are increasing.
Here you can find further information on the causes and consequences of climate change: "Climate Change - The Greatest Challenge for Humankind"
What is special about the growth of city trees?
In contrast to free-standing trees, city trees cannot spread out as well due to the lack of space. The roots of these trees have to be distributed differently because of underground pipes, floor coverings or buildings. Due to this restriction, they form much smaller roots and are more difficult to absorb water.
Usually there is not enough soil in the city floor in which the water can collect. This also prevents urban trees from optimally absorbing water. Sometimes it even does not even reach the roots due to the different floor coverings. In this way, these city trees can experience drought stress much faster.
The many buildings in cities also have a negative effect on tree growth. Trees standing directly on house facades usually grow a little more in the opposite direction. This means that there is an overweight, which is why these city trees can tip over quickly, especially in storms and because of their already smaller roots.
How is climate change affecting our urban trees in particular?
Our precious city trees give us shade in summer and ensure that the entire city does not heat up too much. They also produce oxygen and filter CO2 and other pollutants from the city air. In general, city trees simply increase the overall quality of life in cities. But now comes climate change. What does this mean for our city trees?
City trees are already very disadvantaged in terms of their habitat. Now they also have to fight hard with the ever advancing climate change. The dry periods are currently getting longer, which is why urban trees are increasingly facing drought stress. This means that they are not supplied with enough water and can shed their leaves prematurely. In the worst case, this leads to tree death.
The long periods of drought and rising temperatures also make it easier for the pests to multiply. These pests or other diseases shorten the life of city trees enormously.
In addition to dry periods, instead of normal precipitation, there is often heavy rain. Most of these large masses of water run off above ground or usually seep into the ground so quickly that the roots of the city trees have no way of absorbing water. City trees are also very endangered by extreme weather such as storms.
So this means that large tree deaths can occur. Thus, it is no longer possible for the city trees to donate oxygen to us, the pollutants are no longer filtered out of the city air and our health is endangered in the long term. Cities are becoming pure concrete deserts without their green oases, which we use as recreational areas.
How can we prevent that?
Quite simply, we become true casting heroes and save trees! You always have the option of supplying city trees with water. It doesn't matter whether you use a watering can or a garden hose. The main thing is that the water penetrates to the roots. You can also coordinate in the neighborhood and everyone takes over one or more trees. Through such “casting partnerships”, more and more people are becoming aware that people and nature can live together and help one another.
Organized watering in the neighborhood with a tree bath works best. Here, irrigation bags are placed around the tree, filled with water and drop by drop of the water on the ground over many hours. This gives the roots enough time to absorb the water. Since city trees are often rooted to one another, you can even support several trees at once with a tree bath. Due to the long watering time, it is also possible to see which tree has already been given a water bath and has a full bag and which trees are still waiting for a tree bath with empty bags.