WHY IS MONITORING TREE HEALTH AND DISTURBANCES IN URBAN FORESTS WORTHWHILE?

Urban forests are multifunctional green infrastructures that provide a wide range of ecological, social, and economic benefits. They support biodiversity, offer essential recreational environments for residents, and contribute significantly to climate change mitigation as carbon sinks. However, urban forests are increasingly exposed to various disturbances, creating new challenges for both forest management and municipal decision-making.

If old spruce stands are lost due to forest damage, such as from the spruce bark beetle, the pleasantness of recreational forests will change significantly for decades.

Unlike commercial forests, urban forests are often dominated by older tree stands, as regeneration is typically limited due to land-use constraints and recreational demands. As a result, forest renewal processes differ significantly from those in managed production forests. Large-scale forest management actions, such as tree removal or sanitation fellings, can therefore become sensitive issues and frequently trigger public debate among city residents.

Old forest stands often have high recreational and ecological value, and residents generally wish to preserve their continuous canopy cover. However, disturbances such as damage caused by the European spruce bark beetle can rapidly change the structure and usability of these areas. The loss of mature spruce stands significantly reduces recreational attractiveness, and the recovery of these values may take several decades. Until new trees reach sufficient height, movement and recreational use become more difficult. Standing dead trees may also pose safety risks to visitors, while fallen trees, although beneficial for biodiversity, can restrict accessibility in heavily used areas.

Healthy and growing urban forests deliver multiple long-term benefits for municipalities. They function as important carbon sinks, enhance residents’ well-being, and generate economic value through ecosystem services. Consequently, the weakening of carbon sinks due to bark beetle damage directly challenges municipalities’ climate commitments and long-term sustainability goals.

The European spruce bark beetle is one of the most significant forest pests in northern and central Europe, capable of causing extensive damage in a very short time frame. If infestations are not detected early, damage can escalate rapidly within a single growing season. Systematic mapping of bark beetle-infested trees provides municipalities with timely and spatially accurate information on emerging risks. 

When breeding trees are identified, there is a high likelihood that nearby stands will soon be affected as beetle populations expand. This knowledge enables forest management measures to be targeted efficiently and proactively. Annual monitoring and mapping allow municipalities to track the spread of disturbances, assess their impacts on urban forest structure, and support the development of long-term forest management strategies. In recreational areas, resilience can further be strengthened by regenerating high-risk stands with a diverse mix of tree species.

Mapping bark beetle-infested trees helps cities maintain a healthy and safe environment and protect local nature.

The results of the mapping process are compiled into comprehensive forest health reports prepared by forest health specialists. These reports provide a clear overview of current conditions and future risks, supporting informed decision-making and transparent communication with residents. Expert analyses and situational assessments also help justify necessary management actions in publicly sensitive environments.

Urban forest management must simultaneously consider additional ecological values. The protection of sensitive wildlife habitats is essential, as certain species, such as flying squirrels, depend on mature spruce trees for nesting. Similarly, bird nesting sites must always be taken into account when planning tree removal. Balancing forest health, safety, biodiversity, and recreational use requires reliable and up-to-date information.

Forest disturbances will continue to influence the planning and management of urban forests in the coming decades. Proactive monitoring and mapping of bark beetle-infested trees help municipalities maintain healthy, safe, and resilient urban forests while safeguarding biodiversity and ecosystem services.

Does your municipality have an up-to-date and comprehensive understanding of the health and disturbance risks of its urban forests? Does this information sufficiently support decision-making, climate objectives, and public safety?

Access to reliable forest health data enables proactive management, reduces risks, and supports transparent, evidence-based decisions in urban forest planning. Read more about Forest Health analysis.

In some areas, the number of dead trees has doubled within a single year. Here is an example from a single urban forest: high-resolution false-color satellite images from August 2022 and September 2023 show dead trees highlighted in green. The images depict the same location, illustrating how quickly tree mortality can increase.