Tree cover needed to curb city heat

Greening British cities will become increasingly important in future decades as the urban heat island effect will see summer temperatures soar above 40 degrees.

Launching its paper Eco towns and the next 60 years of planning at the Labour Party conference on Monday, the Town and Country Planning Association (TCPA) said climate change and the ever-increasing demand for housing would put a dual pressure on planners in coming years.

The effects of global warming will be keenly felt in cities as large swathes of asphalt act as a giant storage heater, absorbing heat during the day before releasing it at night.

Increasing tree cover and green spaces by even small amounts can make a significant reduction to this effect, by enabling evapo-transpiration which cools the air.

Rob Shaw, TCPA director and author of the report said: “Research points to some clear solutions: adding just 10% to the existing green cover of high-density areas can keep maximum surface temperatures below today’s levels up to the 2080s.

“Combining this with a comprehensive programme of green roofs will actually keep maximum temperatures below current levels throughout the century. On the other hand, reducing green cover by 10% will see a dramatic increase [in temperatures] in highdensity areas.

“Increases like this would see many cities, particularly in Southern England, experiencing temperatures of over 40C on a regular basis and for increasing periods of the summer.”

New buildings must also be designed to take into account increasing temperatures and pressure on water resources, says the TCPA.

“We have to adapt the way we build and live in our homes to cope with

uncomfortably high temperatures, the strain on water resources, less and less

stable ground conditions and, as we have experienced this summer, more

flooding.,” said chief executive Gideon Amos.

“Responding to this requires innovative use of space within and around buildings.

We need homes and gardens with generous tree cover to both complement the

growing amount of high density development.

Ill thought-through promotion of high density to save land can do much to exacerbate the problems. Large canopy trees, green cover and green roofs where there is no space for a garden at ground level can all help to keep summer temperatures in cities cooler and minimise the risk of urban flooding.”

Sam Bond

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