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.’
