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Like all living things, trees have a limited life cycle, with phases of youth, maturity, and old age. In their prime, trees provide and environmental quality—as well as an undeniable aesthetic value—to urban spaces. However, as they get older they get weaker, and this affects their stability. Old age brings internal rot, hollow trunks, fungal and bacterial infections, and an increased risk of breakage or falling.

In the natural environment, form part of the environmental cycle, and can also provide shelter for wildlife. But in cities where public safety is a priority, these same processes pose a danger that cannot be ignored.

Damage invisible to the naked eye

Managing urban trees requires responsibility and foresight. One of the main problems is that deterioration is not always visible from the outside—a tree's lush, leafy canopy can easily belie a hollow or weakened interior.

Culprits can include , which attack wood for food, breaking down a tree's cellulose and lignin and damaging its internal structure.

The most common types of decay can be sorted into two categories: brown and white rot. Brown rot occurs when organisms such as Paenibacillus glucanolyticus or Serpula lacrymans degrade cellulose and hemicellulose. White rot happens when lignin is degraded by the fungus , also known as "turkey tail."

In both cases, the outcome is the same: the tree irreversibly loses strength. Despite the seriousness of the situation, it is often only possible to ascertain the extent of the damage caused after felling, which confirms whether (or not) the tree's removal was necessary.

In some cases, we can identify a discrepancy between a tree's external appearance and its actual condition by using a . This device assesses the integrity and density of the wood by inserting a thin needle into it.

Different species, different lifespans

Not all tree species have the same life cycle, and fast-growing trees like poplars and aspens live shorter lives than others. Once they reach around fifty years of age, they tend to age quickly: their trunks become hollow, their roots lose strength, and they are at much greater risk of collapse.

While they may have served a valuable purpose for decades, there comes a point when they must be replaced with newer, safer trees. Keeping them beyond their useful lifespan exposes park users and passersby to the unnecessary danger of falling branches.

The felling of a tree can, of course, cause sadness among neighbors, as many trees are linked to memories and form part of a place's identity. However, tree management cannot be guided solely by nostalgia—it has to account for the safety of everyone, and have a clear vision for the future.

Delaying felling when a tree is already in the final stages of its life compromises public safety. The consequences can be serious, ranging from heavy branches falling to a tree's complete collapse, with all the associated risk of personal injury and property damage.

Dead trunks as a wildlife refuge

The removal of aging trees must be accompanied by new plantings, preferably of native or adapted species. This means that longstanding, treasured green spaces can be renewed and even expanded while also enriching biodiversity. It ensures that future generations will inherit healthier and safer parks.

Responsible tree management also includes sanitary pruning, height reduction in at-risk specimens and, in some cases, the temporary preservation of hollow trunks as shelters for birds, bats and insects. Where there is no direct danger, old wood can continue to be useful for wildlife, but in areas of intensive use, human safety must take precedence.

Helping people understand

Urban trees are not mere decorations. They regulate temperature, , and enrich the landscape. They are an essential component in citizens' well-being. Giving them up is not an option, but neither is keeping trees that have exceeded their useful lifespan and pose an unacceptable risk. That is why proper tree management is so important.

In this context, transparency is essential. Clearly explaining the criteria behind why certain trees are being felled can go a long way to reducing public mistrust. If people understand that an apparently healthy tree is in fact severely damaged and poses a danger, they will much better understand the need for action.

If the decision is accompanied by a policy of replacing the felled tree with a greater number of new ones and greater species diversity, public support can even be strengthened.

Citizens and nature, in harmony

The life cycle of trees forces us to recognize that they are not eternal. They are born, they grow, they age and they die. In urban, public spaces, this process poses a particular set of challenges.

Responsible tree management must anticipate decay, assess hidden risks, plan for removal when necessary, and ensure replacement with new plantings. Only in this way can city parks remain safe, beautiful and full of life, as spaces where nature and citizens can coexist in balance and harmony.