'We need trees' Urban vision fails to take root

From Madrid to Berlin and Paris to Budapest, scientists and planners agree, trees, trees and yet more trees can help make Europe's cities more comfortable even survivable - as global heating strengthens its grip.

- Jon Henley

But concrete pavements, highrise buildings, historical squares and underground car parks are a hostile environment for trees, and authorities are finding it hard to plant more. In fact, many EU cities are less green than they were a century ago.

"It's a massive challenge," said Christophe Najdovski, the deputy mayor for revegetation and green spaces on Paris city council. "We know with enough trees we can lower the city's summer temperature by up to 8C. They're basically natural airconditioning. But planting them isn't always easy."

The latest report from the Intergovernmental Panel on Climate Change could not be much clearer: trees in cities combat climate change directly, by storing carbon, and indirectly, by cooling urban areas reducing energy demands. They also offer "multiple co-benefits": improved air quality, reduced heat stress, fewer "urban heat islands" and "improving mental and physical health".

For city halls, in short, planting more trees should be a no-brainer. But according to the Organisation for Economic Co-operation and Development, tree numbers in many European cities have been falling since the early 1990s, with some conurbations losing as much as 10% of their cover.

In part, experts say, that is because older trees from the late 19th and early 20th centuries - those that survived generations of urban planners' efforts to make more space for cars - are starting to reach the end of their lives.