The threats and solutions to urban tree pests and pathogens in a changing climate

Project Information

TREEPACT

Grant agreement ID: 101023713

DOI

10.3030/101023713

Project closed

EC signature date 13 March 2021

Start date 1 May 2021

End date 7 October 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 244 209,60

EU contribution

€ 244 209,60

Coordinated by

TECHNISCHE UNIVERSITAET MUENCHEN
Germany

Periodic Reporting for period 1 - TREEPACT (The threats and solutions to urban tree pests and pathogens in a changing climate)

Reporting period: 2021-05-01 to 2024-04-30

Summary of the context and overall objectives of the project

TREEPACT – Impacts and Solutions to Urban Tree Pests and Diseases in a Changing Climate

Urban trees and forests contribute significantly to the urban environment. A healthy tree canopy cover is essential to help cities adapt to rising temperatures. Greening programmes to expand urban tree canopy cover have gained global prominence recently. However, urban trees and forests are increasingly threatened by native and non-native pests/diseases. Examples include the fungal pathogens Phytophthora ramorum and Ceratocystis platani, the oak processionary moth (Thaumetopoea processionea) and the Asian long-horned beetle (Anoplophora glabripennis).

These pests/diseases may affect trees through defoliation or boring, cause branch fractures, tree mortality, and even negatively impact human health (e.g. dermatitis caused by caterpillar hair). Climatic changes, growing international trade, and declining biodiversity will likely increase the risks posed by tree pests/diseases. Monocultures and drought-stressed trees are particularly vulnerable to pests/diseases. Understanding these growing threats, including perceptions of them and management responses, is critical for developing efficient strategies for urban tree and forest health. However, past research mainly focused on forests in the wider countryside, leaving considerable knowledge gaps in the context of urban areas.

Overall Goal and Research Questions
TREEPACT aims to increase understanding of the growing threat of urban tree pests/diseases to support urban policy and management. The project was guided by three key questions, organized into three work packages (WPs):
1. WP1: What are the socio-economic and environmental impacts of tree pests/diseases in urban contexts?
2. WP2: How do different stakeholders understand and respond to urban tree pests/diseases?
3. WP3: What is the policy and management response to urban tree pests/diseases?

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

WP1: What are the socio-economic and environmental impacts of tree pests/diseases in urban contexts?
In this WP, I reviewed global scientific knowledge on the impacts of tree pests/diseases in urban areas. After screening over 3000 journal articles, 100 articles from 28 countries (1979-2021) were selected, and impacts categorized into: (1) environmental impacts (95% of the studies), including tree damage, tree mortality, reduced growth and functional changes to trees; (2) social impacts (35% of studies), comprising aesthetics, human health and safety; and (3) economic impacts (24% of studies), including pest/disease management costs and economic losses. Pest/disease management responses were also documented. Evidence gaps exist on the effects of pests/diseases on the climate-regulating capacity of urban trees and forests, including their ability to regulate local temperature and reduce flooding and soil erosion. Little was found on hazards, nuisances, property damage, and liabilities caused by tree pests/diseases. This synthesis provides evidence of tree pest/disease impacts to guide policy, management and research. Outcomes include a project website, a scientific review article, and an open-access dataset. Two additional articles were published, and results were presented at conferences, seminars, and via (social) media.

WP2: How do stakeholders understand and respond to urban tree pests/diseases?
I conducted an online survey of 186 stakeholders associated with urban trees and forests in Germany (e.g. tree care professionals, foresters, urban planners, property owners, estate managers, and hobby gardeners). Most respondents (75.8%) considered tree pests/diseases a severe problem and 51.1% had high self-reported knowledge of pests/diseases. However, there was limited awareness of certain quarantine pests/diseases and management options. Respondents were most affected by the horse chestnut leafminer (61.3%), ash dieback (58.1%) and oak processionary moth (50%). Widely used remedial measures included improving tree conditions (60.8%) and purchasing plants from trusted sources (59.7%). Statistical analysis showed an association between knowledge and management responses (11.7%). The findings indicate that efforts to improve urban tree health must be intensified and tailored to different stakeholder needs. Four articles were published, one in a German-speaking journal, and results were further disseminated via four conferences, three seminars and (social) media.

WP3: What is the policy and management response to urban tree pests/diseases?
In this WP, I reviewed relevant environmental approaches in the German city of Munich to assess their role in addressing tree pests/diseases. These included regulations, policies and programmes linked to urban green spaces, trees and forests. The results suggest limited attention is given to the specific issue of tree pests/diseases at the city level, indicating gaps between local actions and national/international biosecurity efforts. Management responses around the globe (WP1) and on the German national level (WP2) were also examined. The findings suggest that stakeholders associated with urban trees may need more knowledge of possible remedial actions. While many cities have developed tree strategies to expand canopy cover, there is an urgent need to better support urban trees and forests, especially against accelerating pest/disease infestations and climatic changes. Results were communicated via two journal articles and two book chapters. Recommendations will be expanded through the EU Cost Action network ‘Urban Tree Guard.’

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

TREEPACT addresses urban environmental challenges in the context of climate change, plant health and human health. It informs new policies and management practices related to urban trees and forests. More specifically, the project raises awareness of the growing threat to urban trees and provides solutions. The research offers new insights into tree pests/diseases, supporting European policies like the European Green Deal. It also synthesizes existing knowledge on the impacts and solutions to tree pests/diseases.

Short-term benefits include new and synthesized knowledge on urban tree pest/disease impacts, risk perceptions, management options, and a reference database. Long-term benefits (>10 years) are expected to include a transdisciplinary knowledge base, collaborative research initiatives and training the next generation of experts in the field. The project is expected to help reduce pest outbreaks and their spread, improving urban tree health in the longer term.

Findings from TREEPACT have been disseminated widely to enhance societal impact, reaching several thousand stakeholders. As a result of this project, I have also become involved in the EU COST Action network ‘Urban Tree Guard’, where we are collaboratively developing further policy and management recommendations and guidelines. The desired effect is a reduced risk of tree pest/disease entry and establishment in urban areas. Ultimately, the project aims to ensure healthier urban trees to benefit the urban environment and human well-being.

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