Communicating Risk and Response of Invasive Tree Pests in Urban Forests: A Need for Context in Contemporary Media

Edited - 7 min read

Informing residents on detections of invasive tree pests can contribute to timely awareness, increased community engagement, and public trust in the management of urban forest risks. These updates, most recently regarding Dutch elm disease (DED), are typically brief with news stories distilling complex ecological and management realities into simplified narratives.

While contemporary media enables rapid access to information, the format of the medium itself can narrow and inadvertently shape perceptions of invasive tree pest risk and response within the context of long-term urban forest resilience and sustainability.

The sections that follow examine the implications of limited context in contemporary media narratives about invasive tree species and their management while proposing strengthened partnerships as an essential strategy in meeting escalating climatic, ecological, social, and infrastructural challenges that increasingly jeopardize the long-term sustainability of urban forests.

Quiet Storms Beneath the Bark

One challenge associated with supporting public understanding of invasive species detections is communicating that the absence of detections does not necessarily mean the absence of risk.

Understanding more about Dutch elm disease (DED) and how it infects and kills elm trees can help. DED is a fungus that clogs internal water-transporting vessels (xylem) and leads to the death of the infected tree. Further spread of this fungus to other trees occurs underground through complex root systems and containment of DED requires removal of nearby elm trees.

Until symptoms of an infection are outwardly observed, the absence of DED could be assumed. Some might think, ‘if a tree looks healthy, then it probably is, right?’ This is not necessarily the case. As long as the fungi that cause Dutch elm disease, Ophiostoma ulmi and Ophiostoma novo-ulmi , that are carried on external body surfaces of bark beetles is present, the potential for new infections remains. This is where ongoing surveillance and vigilant monitoring for DED and another more devasting pest, the emerald ash borer (EAB), rely on strong collaboration among municipalities, provincial and federal partners, non-profit organizations, and community members to help protect urban forests. When detection occurs, it is evidence that current systems are working as intended, supporting efforts to prevent further spread and protecting remaining tree inventories.

In addition to understanding the invasive ecology of these pests is consideration for a multi-faceted approach in long term protection and management of urban forests. This includes sustained investment in multidisciplinary surveillance and monitoring programs, locally-sourced tree nursery networks, innovative local field research, and community education and engagement. Historical reviews of past invasive species management approaches have repeatedly demonstrated that no single tool is sufficient and over-reliance on singular practices leads to devastating results.

The Ecology of Susceptibility

Understanding the risks and impacts associated with compounding environmental factors that shape urban tree health and vulnerability to invasive tree species takes time and context that short public updates are not always able to capture.

Ecological interactions are the relationships that connect living things to one another and to their surroundings. When these relationships are functioning well, they contribute to healthy, resilient urban forests capable of supporting biodiversity, providing ecosystem services, and adapting to changing conditions. Trees depend on a combination of living (biotic) and nonliving (abiotic) factors that together influence their growth, health, and long-term survival. Nonliving organisms (abiotic) are essential to tree health, but are often degraded in urban environments. They include compromised soil structure and soil ecology, poor air quality, climate-driven weather extremes, and physical or mechanical damage. Together, these stresses impact a tree’s capacity to thrive, weaken its defense systems, and narrow recovery windows.

Living factors (biotic) are equally important. Many organisms contribute positively to urban forest health, including pollinators, decomposers, soil microorganisms, predators, and other species that help maintain ecological balance. However, some biotic factors can be detrimental to tree health, including invasive insect species, pathogens such as bacteria, viruses, and fungi, competing vegetation, and harmful human or wildlife activity.

Abiotic and biotic factors exist in a dynamic balance. When that balance is disrupted, tree susceptibility can increase and broader signs of ecosystem stress may begin to emerge. Invasive insects and pathogens are more likely to establish in stressed, weakened trees than in healthy ones. They are especially successful in cities where urban forests may have limited tree species diversity, where busy human activity accelerates their movement, where geographically fragmented green spaces create stressed ecological boundaries, and where the slow pace of tree growth, long-term planning and budget cycles are easily outpaced by rapidly spreading invasive species.

When Zero Becomes A Blind Spot

When narratives are suggestive of expectations that center on zero detections as a target to be achieve or maintained without sufficient context, it can constrain opportunities for learning and adaptation. It may also inadvertently reinforce false assumptions of predictability and control, shaping risk perception in ways that oversimplify invasive species ecology. It can also overlook the inherent variability of natural systems.

A fuller context could include understanding the ecological and human-driven factors that enable invasive species to establish, spread, and cause harm. They include the ability to travel vast distances via global trade and international travel, extend biotic and abiotic stress loads experienced by urban trees, exploit genetic vulnerabilities that are rarely challenged within a tree's native range, capitalize on an absence of natural predators, parasites, pathogens, and other ecological controls which help regulate pest populations. These factors tip the scales, leading to an unfavourable advantage over native trees, plants, and local ecosystems.

It is equally valuable to consider historic urban forest design decisions and the climate context of prairie cities. Because natural tree cover was historically limited across much of the Prairies, elm and ash became foundational species in both rural and urban landscapes. They were widely planted for shelterbelts, streets, parks, and yards because they grew quickly, provided shade and wind protection, and tolerated the extreme temperatures and challenging growing conditions commonly found on the prairies. The historical reliance on elm and ash has shaped the character of many Prairie communities, but it has also created conditions where Dutch elm disease (DED) and emerald ash borer (EAB) can have far-reaching ecological, social, and economic consequences.

Reflecting more deeply on these dynamics and on how risk is framed may help inform more effective invasive species management approaches moving forward. In doing so, it could lead to opportunities that inherently strengthen public literacy and sustained stewardship thereby diversifying the resources required for progressive surveillance and management approaches.

Systems-Thinking for the Long Game

The introduction, establishment, spread, and management of invasive species are influenced by a complex network of ecological, social, economic, and institutional factors. Understanding these connections through a systems-thinking lens highlights the value of adaptive management strategies.

A systems-thinking perspective recognizes that long-term urban forest resilience depends not only on individual management tools, but also on the relationships, communication pathways, and adaptive capacities that connect them. From this perspective, invasive species can be viewed not only as biological pressures, but also as indicators of how effectively existing systems are functioning. It invites renewed examination of whether approaches, once successful, will remain sufficient under changing conditions. They can also reveal opportunities in identifying unrealized resources that can strengthen management responses.

Knowing that DED and EAB spread without regard for jurisdictional, ecological, and social boundaries, the risk that spread and establishment represents in terms of scale of impact highlights the need for broader collaboration. Equitable participatory governance models create opportunities for community stewards, technical experts, and governing organizations to work together in identifying challenges and develop solutions that shape positive urban forest outcomes. They also uphold unique cultures, recognize lived experience and place-based knowledge, develop stronger social cohesion and shared ownership of public spaces. Community-led initiatives, such as citizen science projects, are characteristically adaptive and creative in scope and application. They have demonstrated success in complimenting and extending early detection and monitoring efforts, thereby slowing their spread.

Urban trees are not an optional urban enhancement, they are fundamental to healthy cities. Those ecosystem services that sustain life, as naturally distributed within urban forest systems include air purification, carbon sequestration, temperature regulation, stormwater management, soil stabilization, and habitats for birds, mammals, and pollinators.

Trees produce the oxygen we need to breath.

Trees support mental health and wellbeing, contribute to cultural heritage and placemaking, and support a sense of safety and social cohesion. Cumulatively, they reduce energy costs, increase property values, and extend infrastructure lifespans.

As pressures on municipal systems intensify, the broad benefits provided by urban forests reinforce the importance of their continued protection, stewardship, and long-term investment.

When Loss Leads

Deliberate learning from jurisdictions that have experienced the devastating loss of urban trees to invasive species such as DED and EAB can help normalize conversations about these threats and channel public concern toward meaningful and sustained acts of stewardship.

This framing invites us all to see trees beyond the blurring effects experienced from our vehicles, bikes, and busy-ness of our lives. To see trees as the living organisms that they are and in doing so, communicates the timely need for shared responsibility and renewed investment in their long-term care.

By providing context around how and why invasive species affect the trees nearest to us, we can better understand how these impacts shape daily urban experiences and overall quality of life. This makes it more likely we will champion for their protection.