Background: Heat-related stress is aggravated by the urban heat island effect. With air temperatures up to 8oC cooler in greenspaces than in the surrounding urban area, a cooling effect extends out beyond the greenspace boundaries providing localised relief.
Objectives: We map the extent to which London’s greenspaces cool the resident population in an attempt to value the cooling service they provide and the merit of increasing greenspace provision to reduce heat-related stress under a changing climate.
Methods: Based on the literature, a cooling boundary was designated for different sized greenspaces. Using a geographic information system, the total cooled area in Inner and Greater London was modelled and the proportion of the population cooled was calculated. We focus on societal groups susceptible to heat-related stress: people over 75 years old, children under 4, and people with compromised health.
Results: Assuming equal population distribution across residential areas in Greater London 1.1 million people live in areas cooled by 2oC by greenspace, in Inner London that figure is 0.4 million. Based on these figures we estimate that this cooling saves 4 lives per day across Greater London and 2 lives per day across Inner London during extended periods of high temperature. An average 74% of Inner London and 46% of Greater London is not cooled by greenspace.
Conclusions: Averting a premature death has been valued at £1,653,687. Collectively valued £9.1 million per day when air temperatures exceed 24oC, greenspaces should be protected to sustain this cooling long term. New greenspaces strategically placed across Greater and Inner London would provide heat-stress amelioration to an additional 6.6 million people. These should be at least 2 ha in size.
