Denise Bester: 'Green roofs' help cushion urban footprint

There's a lot to love about cities. The activity, the vibrancy, the culture. What's usually missing, though, is nature. This lack is often what drives people to "downsize" and shift into the country.

The concrete jungle, aside from an aesthetic lack of greenery, has many negative environmental impacts. The large built-up area absorbs the sun's energy and re-radiates it, causing the urban "heat island" effect. Hard, non-porous surface areas cause run-off when it rains (stormwater), which collects pollution residues, ending up as contaminated water in our drains.

The lack of continuous natural areas disrupts species populations and discourages biodiversity. And finally there's the large amount of "wasted" space on all those building rooftops.

What if a city could support natural ecosystems? What if it could blend into the rural surrounds, manage some of its own byproducts, clean its own air and even produce its own food? Such a city would use green roofs.

Relatively new in New Zealand, green roofs, or living roofs, were first used several centuries ago in Europe to provide insulation, and are now designed to provide a "natural landscape" in an urban setting. They can range from native, low maintenance landscapes (extensive gardens), to a complete recreational green space, or even an urban farm (intensive gardens).

The advantages of green roofs are numerous. Which ones benefit a city most, Landcare Research says, is dependent on location. In heavily urbanised areas like Tokyo or China, green roofs dramatically minimise the heat island effect, keep buildings cooler and improve air quality. In New Zealand, they are most beneficial for stormwater management, and in London green roofs are used to increase biodiversity.

An organisation called Green Roofs for Healthy Cities believes that the psychological benefits of green roofs are worth a mention too. Studies have shown that people living in high-density developments are known to be less susceptible to illness if they have a balcony or terrace garden. In fact, one study involving patients in the same hospital, recovering from the same operation, found that the patients with a landscaped view had shorter post-operative stays, took fewer painkillers and had fewer negative evaluation comments from the nurses.

Green roofs can also be highly productive. A project in Brooklyn, New York, has reclaimed a large warehouse rooftop, turning it into a thriving urban farm. It's a 6000sq ft (1828sq m) garden producing a range of vegetables which are sold to neighbouring restaurants. Locals drop off their kitchen scraps, grab a spade and get involved. We have a few green roofs to be proud of too, including those at Auckland University, Waitakere City Council, Conservation House in Wellington, and the Sir Edmund Hillary Alpine Centre in Mt Cook, as well as a sprinkling of residential properties.

Perhaps, instead of escaping from the city to the country to find a more wholesome lifestyle, the smart answer is to move the country to the city.

* Denise Bester is from the sustainable living website www.ecobob.co.nz