Trees are true marvels of nature: they provide shade, purify the air, offer habitats for countless animal species, and enhance our quality of life. Especially in urban areas, trees play a pivotal role in addressing the challenges of climate change, such as heatwaves and air pollution. However, maintaining these green giants requires expertise to ensure their valuable functions are preserved for generations to come.
This information sheet (here is the original Deutsch version), inspired by the collaboration between the Climate Change Adaptation Model Region (KLAR!) Amstetten and “Natur im Garten” (partner of Arcadia project) provides practical guidance for municipalities on tree care and demonstrates how old trees can be sustainably protected as vital elements of our environment: a contribution to a climate-resilient and biodiverse future.
Why old trees are so important in urban areas?
The famous writer Theodor Fontane once called tree-lined avenues “green groves of travel”. Trees have always been important to people, offering protection, shade, and cultural value.
But why should we preserve old trees and plant new ones in our cities, even when space for parking seems scarce? The answer is simple: because people live, work, and rest here. We need the diverse benefits of trees right where we spend our lives.
- Cooling Effect: trees can evaporate significant amounts of water—often over 100 liters per day. This “evaporative cooling” is especially noticeable on hot summer days, making city life more comfortable. Remarkably, it takes 2,000 young trees to match the ecological function and benefits of a single mature beech tree.
- Air Purification: through their leaves, trees absorb not only carbon dioxide but also gaseous pollutants like nitrogen oxides, ozone, sulphur dioxide, and carbon monoxide, improving urban air quality.
- Dust Filtration: trees capture fine dust from traffic on their large leaf and branch surfaces.
- Temperature Regulation: by providing shade and evaporative cooling, trees lower the perceived temperature and slow the formation of ground-level ozone.
- Biodiversity: old trees are vital for wildlife. Around 90 bird species nest in or use tree hollows—features only found in mature trees. Avenues of old trees act as green corridors, linking habitats and supporting species from insects and birds to mammals like squirrels and bats.
Urban green spaces, including mature trees, have been proven to enhance life satisfaction and improve both mental and physical health. Trees are not just beautiful: they are essential for our well-being and the health of our cities.
Tree inspections and tree registers: ensuring safety and preservation
Regular visual inspections of mature trees are crucial for both public safety and tree health. These checks help identify damage, disease, or hazards such as dead branches or fungal infections early on.
A tree register (or tree cadastre) is an essential tool. It is a comprehensive database recording the location, species, age, condition, inspection results, and maintenance history of each tree. This systematic documentation ensures long-term traceability, aids in planning future care, and provides legal evidence in case of accidents.
Inspections and documentation should always be carried out by qualified professionals, following established standards (such as ÖNORM L 1122 and L 1125 in Austria).
Proper care for old trees
Only after several decades do trees reach their full potential in providing ecosystem services. To ensure they continue to thrive, expert care is essential.
Key principles of tree pruning
- Protect the Bark: the bark is the tree’s primary defence. Any injury, including from pruning, can invite wood-decaying fungi. Pruning should be limited to necessary cases, such as shaping young trees or ensuring public safety.
- Correct Pruning Technique: when removing a branch, never damage the branch collar (the ring-shaped swelling at the base of the branch). Always cut just outside the collar to allow the tree to heal efficiently. Avoid leaving stubs, as they can become entry points for pests and diseases.
- Deadwood Removal: regularly remove dead branches to support healthy growth and minimize the risk of fungal infections and falling branches.
- Crown Maintenance: address broken, crossing, or rubbing branches, and clear branches away from buildings, traffic signs, and other structures.
- Timing: contrary to past practices, the best time for pruning is during the growing season (May to September), when trees can heal wounds more effectively.
Special measures: crown stabilization
In some cases, instead of heavy pruning, crown stabilization can be used to secure weak or damaged branches without harming the tree. This may involve static supports or flexible cables to reduce stress and prevent breakage, always installed and regularly checked by professionals.
What to avoid: the dangers of tree topping
Tree topping (drastic cutting back of the crown or large branches) is never a proper tree care practice. It severely damages trees, disrupts their natural balance, and significantly shortens their lifespan. Topped trees are more prone to disease, decay, and require costly ongoing maintenance.
Topping should only ever be considered in extreme emergencies, and only under professional guidance.
Protecting our green heritage
Old trees are invaluable assets: ecologically, aesthetically, and for our well-being. Their care and preservation require knowledge, respect, and a long-term commitment. By following best practices in tree care and management, we ensure that these living monuments continue to enrich our communities for generations to come.
Together, let’s nurture our trees: for a healthier, greener, and vibrant future.
Ph. by Konrad Pistol on Unsplash