Life at
the Top

Dusty Gedge
describes how environment and security concerns can lead to fruitful cooperation, even in one of the world’s most turbulent regions.

People rarely lift their eyes skyward as they walk along a busy street. But if they were to fly over most of the world’s cities, and look down, they would see a bland patchwork of blacks and greys – their roofs. We can harness these uniform deserts to our, and the planet’s, advantage.

Thousands of years ago people in such places as Norway and Western Ireland realised that placing turf on roofs provided simple and effective insulation. Today green roofs are commonplace on buildings from private houses to hospitals, factories and office blocks in countries like Germany and Switzerland.

There is growing interest in the Netherlands, Sweden, Denmark and Hungary. North American cities from Portland to Atlanta are promoting their use, while the city of Kawasaki in Japan has long been greening buildings to reduce air pollution and reduce the urban heat island effect

Greening building
Modern interest in green roofs began in Germany in the 1970s, stemming from observations of vegetation growing spontaneously on traditional ones. They are now a legal requirement in many areas. Under planning law, green space must be replaced when new developments are constructed, and there are financial incentives for green roofs. They are seen as providing a service to cities such as Karlsruhe and Stuttgart by holding water and letting it evaporate back into the atmosphere, reducing the impact of storm water on drainage systems and the incidence of flash floods.

This is also one of the main driving forces for installing green roofs in North America, where increased hard landscaping in cities and channelling of rivers have made floods a major problem. In Portland, Oregon, the metropolitan authority is considering a major green roof policy partly to help maintain good water quality in the Willamette River, thus protecting its salmon population.

Multiple benefits
Yet retaining storm water is only one of the multiple benefits that green roofs bring to cities. They also, for example, provide insulation by acting as thermal barriers. Their effectiveness may be limited in wet winter conditions, but in summer they can help reduce the need for air conditioning. The City of Chicago has estimated that they could save in the region of US$100 million a year in this way.

Peak demand for electricity could be reduced by 720 megawatts, it believes, reducing carbon dioxide emissions: rising summer temperatures, due to the urban heat island effect – and a connected increase in air pollution – can also be moderated. Atlanta is also promoting their use, greening the roof of its City Hall as a showcase. Starting with just 3,000 square feet of green roof space, it expects this area to multiply tenfold within the next few years.

Protect biodiversity
In Switzerland, green roofs have been developed to protect biodiversity. Construction law in Basel requires that all new flat roofed buildings are covered in some form of vegetation: official guidelines stress the importance of roof gardens for endangered beetles and birds.

Platform roofs
Five big green roofs at the Moos filtration plant on the outskirts of Zurich, built in 1913, are now one of the last remaining examples of central Swiss wet grassland. They are so important for orchids that the federal government is considering classifying them as a national park! And new platform roofs at the city’s railway station have been designed to resemble a stony desert, to help conserve a rare lizard. Concern for biodiversity is also driving growing interest in the UK, which has shown little interest in using green roofs for ameliorating surges of storm water, despite the pressure these place on London’s antiquated drainage system, releasing sewage into the Thames. Up to now the roofs have been seen only appropriate for ‘alternative’ or environmental establishments, but they are beginning to now come into their own through a plan by the London Biodiversity Partnership to protect a rare bird, the black redstart. Over 250,000 square metres of green roofs are planned to provide habitat for it, at such notable development sites as King’s Cross railway station, Battersea power station, and the Greenwich Peninsula. And a leading insect conservation organisation, Buglife, is pushing for their use at a new development at Shellhaven, Canvey Island, an area particularly important for rare insects.

Air pollution
Good green roofs can not only ameliorate storm water discharges, air pollution, noise and energy use, but turn cities into refuges for rare species endangered by industrial farming in the countryside. Perhaps our cities’ roofscapes will cease to be deserts and become unique wildernesses, providing havens for nature as well as making healthier and better places for people to live

Dusty Gedge is co-founder of

PHOTOGRAPH: Martin Bond/ Still Pictures

This issue:
Contents | Editorial K. Toepfer | Challenges and Opportunity | Bridging the Water Gap | Golden Gateway to Green Cities | The Spirit of “Mottai Nai” | Cities without Slums | People | Rapid Progress | At a glance: Greening Cities | Charging into the Future | Star profile: Tokiko Kato | The Female Factor | Unlocking People Energy | Think Local | High Achievements | Life at the Top | Books and products | Focus On Your World | Black Sea, Green City?

Complementary issues:
Issue on Human Settlements 1996
Issue on Biological diversity 2000