The ecosystem service delivery of urban green infrastructure (UGI) is now manifest.
Types and level of service provision, however, can alter radically, based on factors such as
location, species choice, planting design and vegetation management. The value of vegetation to
provide a cooling service is generally understood in hot climates, but the merit in temperate
climates remains ambiguous. Indeed, policy makers within cooler countries (e.g. UK) remain to
be convinced that expenditure on UGI is justified, at least from the point of view of city cooling
alone. Occasional warm days do occur of course, and climate change models predict that heat
wave events will become more frequent within the UK, including those that pose a risk to
human health. To help UK policy makers make better-informed decisions around UGI, a number
of our research programmes have targeted the role vegetation plays in regulating temperature,
but specifically within the context of a maritime-temperate climate. Two examples of ‘green
interventions’ are discussed here. The first documents the role of green façades to cool a wall
system and the second illustrates the cooling influence conferred by roadside trees. Both
experiments used a replicated sampling approach to ensure statistical robustness, and hence
convince policy makers that data is representative of UK scenarios and results are reproducible.
In the first experiment, 10 separate wall sections are used to investigate the cooling influence of
two different plant genotypes (Prunus and Phaseolus) on both exterior and interior wall spaces.
In the second study, road surface temperatures are documented with respect to both built and
green infrastructure, i.e. we compare the influence of buildings and street trees on the surface
temperatures across a road profile. Again replicate data are used to provide a ‘generic’ summer
temperature profile for the city of Sheffield, rather than just specific locations at one point in
time. Results show that green facades can reduce exterior and interior (cavity) wall air
temperature by 3oC and 5oC respectively. Likewise, large street trees have a mean cooling
influence of 4.5oC on road surfaces near their base compared to comparable sections adjacent to
buildings. To maximise cooling, the data suggests that trees need to be provided on both sides of
a roadway, i.e. a single tree did not manage to cool the pavement at the
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)