A comparison of urban tree populations in four UK towns and cities

Trees are a valuable asset to cities and towns, providing numerous services that sustain and support human life. They store carbon, filter airborne pollutants and intercept rainwater. The structure of urban tree populations and how resilient urban trees are to pests, diseases and changes in climate are relatively unknown. Surveys of urban trees using i-Tree Eco were conducted in Torbay, Wrexham, Glasgow and Edinburgh between 2010 and 2013 to assess the ecosystem services provided by urban tree populations. Data from these surveys can be used to analyse tree population structures and to make an assessment of the robustness of tree communities now and in the future. There were similarities between tree populations in Wrexham and Edinburgh that may have been influenced by planting practices or similarities in land use types, rather than climate. Trees were most commonly encountered in parks and in residential areas. The populations of these land use types were also the most diverse. Each study area had at least two species that comprised more than 10% of the population, but no genus exceeded 20% and no family 30%. Torbay possessed the highest proportion of drought resistant species, whilst Glasgow, at risk from flooding, possessed very few waterlogging tolerant species. If urban trees are to survive the future predicted changes in climate, consideration must be given to designing planting on a landscape-wide basis, taking into account species and site-specific properties.