Urban Tree Diversity: Key Lessons from the UTD5 Conference
Urban forests and trees constitute a critical component of sustainable urban ecosystems, offering ecological, social, and climatic benefits that are increasingly indispensable in the context of global environmental change. As cities confront the compounded challenges of climate change, extreme weather events, population growth, and urban densification, the strategic enhancement of tree diversity emerges as a fundamental approach to strengthening resilience and ensuring long-term urban livability.
The 5th International Urban Tree Diversity Conference (UTD5), convened in Madrid, Spain, in October 2024, served as a pivotal forum for advancing this agenda. Building upon the legacy of previous meetings in Sweden, Australia, Canada, and the United States, UTD5 assembled 150 participants from 26 countries, encompassing researchers, practitioners, and policymakers. The scientific program comprised 8 keynote lectures, 44 oral presentations, a round table, 16 posters, and 3 technical visits, fostering interdisciplinary dialogue and knowledge exchange across multiple domains of urban forestry and arboriculture.
The thematic structure of UTD5 reflected the multifaceted nature of urban tree diversity and its role in addressing contemporary urban challenges. Contributions were organized around four principal topics:
Using Tree Diversity to Mitigate Risks from a Changing Climate
Urban forests represent a nature-based solution for climate adaptation and risk mitigation. Presentations examined strategies such as species diversification and integrated green infrastructure to enhance resilience against rising temperatures and extreme weather events, emphasizing the ecological and functional benefits of diverse urban tree populations. The papers included in this section provide empirical evidence and conceptual frameworks for implementing tree diversity as a core strategy for climate resilience in urban environments.
Novel Approaches to Urban Tree Selection
This theme explored innovative methodologies for selecting species suited to complex urban environments. Case studies illustrated the application of advanced data analytics, predictive modeling, and biodiversity principles to optimize tree selection processes, thereby ensuring ecological stability and aesthetic quality under future climatic scenarios. Selected contributions demonstrated how these approaches can be operationalized to guide species choice and planting design in diverse urban contexts.
Emerging Technologies and Their Role in Urban Forest Management
Technological innovation is reshaping urban forestry practices. Contributions highlighted the integration of remote sensing, drone-based monitoring, and data-driven decision-support systems to improve diagnostic accuracy, facilitate early detection of pests and diseases, and optimize resource allocation for sustainable management. The papers featured here showcase practical applications of these technologies and evaluate their potential to transform urban forest governance and maintenance.
Harnessing Open Data and Citizen Engagement to Support Urban Forestry
Effective governance of urban forests increasingly relies on participatory approaches and transparent information systems. Presentations addressed the potential of open-data platforms and citizen-science initiatives to strengthen collaborative management, enhance public awareness, and foster shared responsibility for urban tree diversity. Research included in this section illustrates how participatory frameworks and digital tools can bridge gaps between scientific knowledge and community action, reinforcing inclusive urban forestry strategies.
The three papers selected for this special section, all from North America, exemplify the breadth and depth of research presented at UTD5. Collectively, they advance theoretical frameworks and practical applications that underscore the importance of interdisciplinary collaboration in shaping resilient, biodiverse urban landscapes. By integrating ecological science, technological innovation, and participatory governance, these contributions offer critical insights for the future of urban forestry and arboriculture. They all offer some specific recommendations as well for enhancing urban forest and urban tree diversity.
Sara Barron and colleagues investigate, with the assistance of student researchers, the role of university courtyard areas as diverse and inclusive areas for promoting social connection and wellbeing. The contribution by Andrew Koeser et al. explores ways of enhancing urban tree diversity, quality, and abundance in the Chesapeake Bay Watershed of the United States. The paper by Philip John Potyondy, finally, discusses street tree planting guidelines in the city of Minneapolis from a tree diversity enhancement perspective.
Conflicts of Interest
The authors reported no conflicts of interest.








