Room at the top
With a modest outlay and a certain amount of luck, roofs can be converted into wild gardens, greening the city skies and sheltering the sorts of plants and insects now confined mainly to nature reserves. Green roofs are a new fashion in nature conservation, promoted enthusiastically by the wildlife campaigner Dusty Gedge.

Black redstart
It all began with the black redstart. Gedge is the bird’s official ‘co-coordinator’, his job to persuade developers to help themselves by helping the black redstart. To encourage black redstarts, you need to find ways of bringing more insects into the city. This is where green roofs come in. The technique of developing such ‘wildlife gardens in the sky’ was first developed in Switzerland, where there is a wide variety of possible roofscape habitats. They varied from simple sedum stonecrop mats to relatively lush pastures with wild flowers, sandy banks and even the occasional shallow pond. Nor do the roofs attract the wrong sort of wildlife. Lizards and bumblebees love them; rats and social wasps aren’t interested. More, their promoters claim, green roofs help to prevent flash floods and conserve energy.

Imitating nature
Given its novelty and recent origin, the idea of green roofs has taken off surprisingly well. Dusty Gedge can point to several ambitious and imaginative examples in London and the South East. One is to be on the new headquarters of Barclay’s Bank in Canary Wharf. Another, on the spacious roof of the Rolls Royce factory in Chichester, mimics a gravel pit. Yet another will be on the halls of residence at Royal Holloway College. Prestige is clearly one reason why architects are taking green roofs seriously. Another reason is local authority policy. They have been made a planning condition for new buildings in the area of Deptford Creek. In the Greenwich Gateway 50% of buildings are to have green roofs. Rooftop habitats are by their nature artificial, and their success relies largely on how well they can imitate nature. In London, the ideal might be a roof design that can successfully act as a substitute for the very insect-rich brownfield sites of the Thames estuary.