By Christopher Kennard | Project Manager | RFF
In the recent years, plant diseases have increasingly become a critical concern both in urban planning and in the management of forests. A pathogenic fungus, Ceratocystis platani, has been responsible for devastating canker stains in plane trees, which is raising alarm bells across the Mediterranean region. Specifically in Greece, home to plane trees which adorn city streets, parks, and historic sites, the threats posed by this fungus extend far beyond the negative environmental impacts. Its effects bear the risk of rippling across cultural and economic realms as the values tied to these trees are significant. If left unchecked, the spread of Ceratocystis platani could incur significant financial losses, increased maintenance costs, and adverse effects on tourism and urban aesthetics. By understanding both the scientific background and the broader socio-economic context, local stakeholders can better appreciate the urgency of adopting proactive measures to avoid facing the economic implications of allowing the fungus to spread.
Figure 1: Healthy and Ceratocystis platani-affected trees on Evia Island. Source: AUA.
What is Ceratocystis platani?
Ceratocystis platani is a fungal pathogen that primarily targets plane trees (Platanus species), which are prized for their ornamental value and resilience in urban environments. The fungus invades the tree’s vascular system, leading to canker stain, a condition characterized by dark lesions on the bark and the eventual death of infected tissue(s). As the pathogen spreads, it disrupts the normal physiological functions of the tree and it ultimately leads to a decline in vitality. In a worst-case scenario and when left untreated, Ceratocystis platani can result in tree death.
Research[1] has shown that the fungus can spread rapidly, particularly under favorable climatic conditions: namely warm and humid weather, which are common throughout Greece due to its location. These conditions can create the ideal environment for the proliferation of Ceratocystis platani, and they are further enhanced by the interconnected nature of urban landscapes. Both the weather conditions and spread out inadvertently can unfortunately accelerate the spread of the pathogen. Greece, with its blend of modern urban development and historically significant green spaces, is particularly vulnerable, namely in larger cities, like its capital, Athens, and Thessaloniki. Historically, plane trees don’t only contribute to urban cooling and aesthetic appeal but also serve as symbols of cultural heritage. The loss or decline of these trees could have cascading effects on local biodiversity and urban life quality.
Economic implications of unchecked spread
The economic stakes of Ceratocystis platani’s spread in Greece are high. In urban centers, where plane trees often adorn the streets and parks, these costs can quickly multiply. Municipal budgets are already stretched thin due to other urban challenges. This results in the municipal coffers being further burdened by the management of this fungus. The direct costs associated with tree loss or severe disease management can include, yet is not limited to:
- Tree removal: a complex and costly process that requires specialized equipment and skilled labor to safely remove large and sometimes hazardous trees from urban or forested environments. The process includes hauling away debris, ensuring proper disposal or recycling of the material, and often restoring the affected area. Furthermore, this may require issuance of specific permits and adherence to local regulations, which can further increase expenses. This cumulative cost can place a significant financial burden on municipalities, homeowners, or businesses facing the challenge of managing diseased trees.
- Tree replacement: a significant investment that goes beyond simply planting a new tree. It should entail the acquisition of disease-resistant saplings, proper soil preparation, and the installation of specialized irrigation systems to ensure the young tree’s survival. Deployment of professional labour and equipment is paramount to ensure their proper planting and maintenance. This is not without the respective costs, as previously mentioned, such as one-off costs, relative permits, and the subsequent aftercare to ensure the plant survives.
- Tree maintenance: is an ongoing expense that requires regular monitoring and care to ensure their long-term health and safety. It encompasses routine inspections, pruning, fertilization, pest control, and health assessments. All these points require specialised skilled labour and equipment, which results in the accumulation of recurring costs.
Beyond the direct expenses, significant indirect expenses can be noted such as the following negative economic impacts:
- Urban aesthetics and tourism: Numerous studies and reports highlight urban green spaces as a factor in securing tourism[2] [3] [4], which is directly linked to increased revenue and improved local business activity. According to the European Commission, green infrastructure is linked to benefits in the tourism sector[5]. As plane trees contribute to the visual and cultural landscape of Greek cities, their loss bears the potential to negatively impact tourism, which is a critical revenue source for many municipalities throughout the country.
- Ecosystem Services: Beyond the element of aesthetics, plane trees offer essential ecosystem services, including air purification, temperature regulation, and stormwater management. Their decline can lead to increased urban heat islands and which also bears higher costs in energy consumption for cooling, additional expenditures on infrastructure to manage flood risks during heavy rainfall. The United Nation’s Food and Agriculture Organisation’s study on urban forestry[6] highlights that investments in tree maintenance can protect cities from the negative impacts of climate and contribute to better quality of life.
- Property Values: The presence of mature, healthy trees was shown to enhance property values[7] , namely in neighbourhoods with abundant green spaces generally seeing higher real estate prices. So if a widespread disease like Ceratocystis platani is left unchecked, it could lead to a noticeable decline in respective property values, which would further strain the local economies and result in reduced municipal tax revenues.
- Forestry and Commercial Losses: Plane trees are also a component of commercial forestry, outside of the urban area. In regions where these trees are part of commercial landscapes, the fungus can lead to a loss in timber quality and yield. If left unchecked this could be devastating for communities that rely on forestry as an economic activity.
The importance of addressing Ceratocystis platani
Tackling the spread of Ceratocystis platani is not only an environmental challenge, but also an economic necessity. The uncontrolled expansion of this pathogen could prove devastating for municipalities, forestry services, and local economies. Early detection and rapid response are key to preventing its large-scale proliferation. Systematic monitoring programmes and modern diagnostic tools, such as molecular testing, enable the identification of infected trees even before visible symptoms occur.
Figure 2: Healthy and Ceratocystis platani-affected trees on Evia Island. Source: AUA.
The European and Mediterranean Plant Protection Organization (EPPO) has long recognised the need for such advanced prevention strategies to contain invasive plant pathogens across natural and urban ecosystems[8]. Prevention demands a multifaceted strategy that blends technology, collaboration, and public awareness. Community engagement, continuous training, and strong policy support are essential for the success of any effective response plan.
STELLA’s Contribution and the Pilot in Evia, Greece
Addressing Ceratocystis platani calls for a holistic approach that merges technological solutions with active participation from citizens and local authorities. The Horizon Europe-funded project STELLA is developing a digital pest surveillance system (STELLA PSS), harnessing cutting-edge technologies such as Artificial Intelligence (AI), the Internet of Things (IoT), remote sensing, and citizen science via smartphone applications.
In Greece, STELLA is focusing on the region of Evia (Figures 1 & 2), where in 2022, Ceratocystis platani caused an ecological disaster—leading to the loss of hundreds of centuries-old plane trees along the island’s rivers. Today, the pathogen continues to threaten both natural ecosystems and residential areas, making timely detection a critical priority.
To respond to this threat, STELLA is implementing an integrated pilot scheme in Evia. The project’s technologies will be deployed in a targeted location, selected based on historical data, field observations, and close collaboration with local authorities. This site will serve as a testing ground for the evaluation of detection and early warning systems, and as a regional monitoring hub for pest outbreaks.
Through this pilot, STELLA aims not only to promote technological innovation but also to contribute to the preservation of the region’s cultural and ecological identity—supporting a more sustainable and resilient management of natural and urban landscapes.
[1] https://www.sciencedirect.com/science/article/pii/S1618866725000846
[2] https://www.researchgate.net/publication/237387268_Irrigation_of_Urban_Green_Spaces_a_review_of_the_Environmental_Social_and_Economic_benefits
[3] https://www.sciencedirect.com/science/article/abs/pii/S1618866717301528?fr=RR-2&ref=pdf_download&rr=92aecb1c88aeee7f
[4] https://www.researchgate.net/publication/383807788_Outlooks_and_Challenges_for_Urban_Green_Space_Development_A_Review_Case_Study_in_Thailand
[5] https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52019DC0236&qid=1562053537296&from=EN
[6] https://openknowledge.fao.org/items/57a6df3d-0ca7-442c-a19a-fc098d108fae
[7] https://library.weconservepa.org/library_items/1033-Shade-Healthy-Trees-Healthy-Cities-Healthy-People
[8] https://www.eppo.int/media/uploaded_images/ACTIVITIES/invasive_plants/pm5-06-1-en.pdf.
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