Economic value of the hot-day cooling provided by urban green and blue space

Increasing high temperatures due to climate change are exacerbated by urban heat island effects, resulting in a range of human health and economic impacts. The green and blue infrastructure (GBI) in cities that underpins nature-based solutions (NBS) can help alleviate hot-day temperatures. In this study we bring together multiple data sources to evaluate the cooling benefit provided by urban GBI in terms of avoided losses in labour productivity, for eleven City Regions in Great Britain, over a ten-year period. We defined the urban extent to include the green (woodland, grassland and parks, gardens) and blue (rivers and canals, lakes and ponds) features within cities, and derived aggregate cooling factors for urban areas in each City Region, applying additional cooling factors to buffer zones around larger GBI features. We collated gridded meteorology data to assess the number of hot-days exceeding 28 °C Wet Bulb Globe Temperature in each City Region over the period 2008-2017, and applied response functions to evaluate loss of worker productivity for ten economic sectors. For the GBI features (aggregated adjacent features >200m2), gardens make up the biggest component (26% of urban extent) closely followed by grassland and parks (24%), with woodland at 6%. The aggregate cooling factor of GBI ranged from 0.64 – 0.89 °C across the eleven City Regions. The economic benefit of cooling was greatest for London, due to its greater exposure to hot days, and its greater contribution to the economy than other City Regions. In the hottest year of 2015, the cooling benefit in London was £13.97 m. The cooling benefit varied considerably from one year to the next, depending on meteorology, and will increase under climate change.