Campaign for greener cities gathers pace

Vegetation to soak up the stifling urban sun

Climate change could wilt British cities in the summer, if we fail to increase the amount of green space, says new research. A report published by the Association for Greater Manchester Authorities identifies an urgent need for green roofs that could counteract the urban heat island effect, by reducing the heat absorbed and released by buildings.

Jon Lovell, Head of Sustainability at Drivers Jonas, the surveyors behind the research, says Manchester currently has around 25 green roofs installed or in planning, but that “there is massive potential to increase that significantly”.

Meanwhile, researchers at Manchester University are measuring the cooling effect of green space with a live trial at nine plots across the city, covered with trees, grass or asphalt. “We’ve seen some promising early results – areas of grass and trees can reduce surface temperatures by about 15°C, which in turn cools the air,” says Dr Roland Ennos. The live trials follow computer modelling tests which suggested that a mere 10% increase in wooded areas in Manchester could cancel out the warming effects of climate change until 2080.

“There’s no denying the benefit of green spaces in urban areas,” says Helen Clarkson, Deputy Director of Forum for the Future. “The mental and physical health benefits of green space have been demonstrated very clearly – through improved air quality and reduced stress, for example. And it’s been shown that regular exposure to the natural environment is important in childhood development. If it can also help to cool cities in a changing climate, then local policy must favour it.”

In July, London Mayor Boris Johnson issued a new environment plan which suggested that two million trees should be planted in the capital to combat rising temperatures. The charity Trees for Cities has welcomed it, but questions whether the target will be met. “They have identified the need, but I’m not sure they have the funds to be able to plant them,” says acting Chief Executive Emma Hill.

German cities such as Berlin and Stuttgart offer excellent examples of urban greening, says Ennos: “The Germans have always been good at this. It is built into the system: they plan green areas with cooling in mind.” – Mark Jansen

1 December 2009

Mark Jansen