Urban trees are increasingly being recognised for the ecosystem services they provide which support the
sustainability and liveability of cities. The quantity of ecosystem services delivered varies between tree species
and is influenced by tree age and health. This Research Report illustrates the change in provision of four ecosystem
services (carbon storage, carbon sequestration, avoided storm water run-off and air pollution removal) by 18 tree
species of small and medium stature which are common to British towns and cities. Data from 3147 field trees, and
simulated tree data where field data were not available, were modelled in i-Tree Eco to estimate ecosystem services
provision. The grouping of trees into five age classifications enabled changes in ecosystem services delivery to be
compared across the trees’ lifespans. The results indicated that, relative to the small stature species, medium species
provide greater quantities of ecosystem services both annually and over the lifetimes of the trees. Trees were also
shown to provide greater ecosystem services in older age classifications, suggesting that management in support of
the long-term survival of trees would contribute to ecosystem services delivery in the urban realm. Tree condition also affected the delivery of ecosystem services, with trees in poor health performing less well than healthy
trees. The presence of small and medium stature species is important for adding species and structural diversity to an urban forest, as well as providing ecosystem services in areas where large trees are unsuitable. Keywords: urban trees; benefits of trees; urban forest; green infrastructure; ecosystem services
