A comprehensive review of research into the heat-mitigating effects of green spaces during heatwaves has found that botanical gardens are the most effective. It is a finding the team at the Global Centre for Clean Air Research (GCCAR) hope will inform policymakers planning cities for a warming world.

This particular research found that sites such as the Chelsea Physic Garden and Royal Botanic Gardens at Kew in London, or the Gardens by the Bay in Singapore, reduced air temperatures during heatwaves in the city streets around them by an average 5C.

Average cooling effect / variation

Botanical gardens: -5.0C / -2.2C to -10C

Wetlands: -4.7C / -1.2C to -12C

Rain gardens: -4.5C / -1.3C to -7C

Green walls: -4.1C / -0.1C to -18C

Street trees: -3.8C / -0.5C to -12C

City farms: -3.5C / -3.0C to -3.9C

Parks: -3.2C / -0.8C to -10C

Reservoirs: -2.9C / -1.8C to -5C

Playgrounds: -2.9C / -2.8C to -3C

This story was covered in The Guardian