Plants are blossoming on high as cities turn the rooftops of their homes and office blocks into little green lungs. Hugh Wilson visits the new urban jungle.
The garden at Tokyo’s Keyakizaka complex is an oasis of calm and shade in the teeming, sweltering city. Fish ponds, rice plants and a cooling breeze soothe harassed office-workers. The car horns and chaos of the streets seem a million miles away.
Or at least 10 floors or so. The 1,300 square metres of the garden sit atop an entertainment and business complex in the trendy Rop-pongi district. It is one of a wave of gardens springing up on rooftops, providing a verdant contrast to the concrete jungle around them. The purpose of Tokyo’s aesthetic. The city swelters in summer as all that concrete radiates heat, and the urban heat-island effect pushes temperatures to unbearable levels. In response, the city’s government has reached for the skies. It has decreed that trees, shrubs, lawns and flowers must cover 20 per cent of new large private buildings and 30 per cent of public ones.
Roof gardens are not new, but their potential as an environmental solution is only now being realised. The largest green roof in the world – at 454,000 square feet – is at the Ford Rouge Factory in Dearborn, Michigan. One of the most spectacular is on Chicago City Hall. Both were created for their environmental contribution as much as their aesthetic effect. Indeed, green roofs are sprouting on public buildings and university campuses across the United States and Canada. Germany, meanwhile, has a history of green roofing dating back to the 19th century, and now uses water rates and building regulations to make sure it stays in fashion. Switzerland takes a similarly approach. Governments, companies and – in some cases – individuals are waking up to the fact that acres of unused roof space can be greened to cut energy costs and promote the ideal of the sustainable city. And with reason. “There is lots of evidence that green roofs absorb pollution, increase the energy efficiency of buildings, create habitats for urban wildlife and act as insulation,” says Jeanette Longfield, the coordinator of Sustain, the UK alliance for better food and farming. “And if you consider that I’m sitting here in London in mid-October and it’s 21 degrees, you can see how necessary it is to promote greener, more sustainable cities.” Gary Grant, an ecologist and the founder of EcoSchemes, a green consultancy company, agrees: “I see green roof as part of the overall greening agenda. Benefits include reducing rainwater run-off, filtering pollutants, cooling in summer and insulating in winter, as well as providing windbreaks, visual screening, noise barriers and wildlife habitat.
They are a prime example of so-called multi-functional design.” Indeed, researchers found that a rooftop garden in Ottawa reduced the heat entering the building in summer by 85 per cent. Large areas of roof greenery reduce the urban heat-island effect, and by soaking up rainwater diminish the chances of flash flooding and overflowing sewers. The initial costs can be high, but lower energy bills and the protection it affords the roof mean that in most cases it will pay for itself. The concept of the “edible building”, where roof space is given over to small-scale agriculture, holds the promise of reducing the environmental damage associated with importing food. Despite this apparent win-win situation – and let’s not forget that a green oasis can do much for employee, patient or resident morale – Britain is dragging its feet. We have some rooftop gardens, but any environmental benefit tends to be incidental to the purpose of providing novel surroundings in which paying guests can dine or dance.
Yet we are aware of the benefits. A research note by the Corporation of London states that “evidence is accumulating to show that [green roofs] can make a unique contribution to the quality of our urban environment.” The Mayor of London, Ken Livingstone, is keen. And there are examples of green roofs making a difference to the local environment, such as the CUE Building (formerly the Centre for Understanding and the Environment) at the Horniman Museum in south London. The CUE roof is a wildflower meadow, living, evolving and adapting in the city’s heart. “The roof supports a large variety of wildlife that is rare in urban environments,” says Lucy-Ann Bishop, the museum’s education and environment project officer. “Even within the limits of the roof, the slopes and chimneys provide varied micro-habitats for different species. There are insects up there that are normally found in dry coastal areas rather than in a busy city.”
The CUE roof is a great example of what can be done, but such initiatives are rare. The reason, experts say, is that few people are aware of the carrot, and the stick is non-existent. “The difficulties with the UK are cost-cutting during development and a lack of money for maintenance,” says Grant. “As yet, the only requirement is at planning permission stage, and that’s if a rooftop habitat is required to provide for a protected species on a brown-field site. The Environment Agency is promoting green roofs but can’t insist on them. Green roofs are still seen as a gimmick or a one-issue solution by many companies and councils.”
Happily, the homes market is taking up some slack. Companies that design and create roof gardens for private houses and flats are doing brisk business, particularly in London. “There’s a huge interest in roof gardens now,” says John Rice of Urban Roof Gardens (www.urbanroofgardens.co.uk). “Certainly, they make a nice space for people to sit or entertain, but we also promote the environmental benefits. Huge areas of London are concreted and can’t absorb rainwater, and that puts the city at risk of flash flooding, but green roof can absorb 80 per cent of the moisture and hold it.” In fact, many experts feel that green roofs are an idea whose time has come. “Green roofs will come to be seen as a useful way in the which the built environment can be adapted to climate change, with more intense rainfall and hot spells,” says Gary Grant. As the effects of global warming become more pronounced, we may all wake up to the promise of gardens in the sky.
31 OCTOBER 2005 THE INDEPENDENT