A new approach for selecting resilient urban trees

Healthy trees are key components of many green spaces. They provide shade, support entire ecosystems, and often have emotional connection for people living nearby. The most prominent trees in urban areas are often the oldest. Trees form a barrier from sound, shielding parks from traffic noise. They provide respite along roads during hot summers, provide seasonal features amidst grey urban buildings, and urban forests provide unique habitats for many different species. Many of these benefits are highly linked to tree size and vitality.

In the paper ‘Resilient trees for urban environments’ researchers explore the importance of understanding the genetic makeup of trees when selecting the right tree for site and function in order to gain all benefits from urban trees.The authors highlight the increasing challenges that urban trees face, with poor growing conditions and outbreaks of pests and pathogens increasing the pressure on tree health. Selecting the most suitable tree species is already an recognised approach, and this research paper takes this approach a step further.?

The authors promote that tree resilience in the urban landscape is enhanced by selecting for intraspecific variation/number of distinct ecotypes. They suggest widespread genetic screening of existing tree collections in botanical gardens and arboreta that would allow evaluation and comparison of different genetically-linked functional traits. Combining this information with identification of which natural habitats match climate and growing conditions within urban environments enables assessment of tree capacity for future climate scenarios in different urban settings.

This approach promotes the selection of trees for urban environments to include those species and provenances most suitable for the environmental conditions and stresses posed by a rapidly changing and unpredictable climate, and the spread of pests and emerging plant diseases.The paper concludes:

“Major efforts now must take place to increase representation of future urban trees in living collections and seed banks, alongside genetic screening of potentially suitable genetic plant material for cultivation. With growing recognition of the current and future values of trees to our societies, we now have to realise these great opportunities.”

As the research into tree genetic variation develops, this research demonstrates how there needs to be a joined up approach. Creating urban green spaces which are resilient to future climate change requires many different components. As part of this, the correct selection of tree species requires connections between those growing and studying the species (such as botanical gardens, plant nurseries and research institutions) and those implementing planting programmes such as policymakers, urban planners and landscape architects. The diversity and success of cities' response to climate change and biodiversity loss is mirrored in the need for diverse and resilient planting alongside collaborative thinking.

Read the full open access article - https://nph.onlinelibrary.wiley.com/doi/10.1002/ppp3.10518?

Article By Francesca Boyd based on the following paper: Sj?man, H., Watkins, H., Kelly, L.J., Hirons, A., Kainulainen, K., Martin, K.W. and Antonelli, A., 2024. Resilient trees for urban environments: The importance of intraspecific variation. Plants, People, Planet.