How green is the green flagship city of the developing world?

During the COP-15 negotiations, where can we find an example of a sustainable city in the developing world?

Google the question and you get an answer: Curitiba in Parana state, Brazil, whose ex-Mayor, Jaime Lerner, is celebrated for pioneering sustainable solutions. Only last month he was in London sharing ideas with its mayor, Boris Johnson.

So I went to Curitiba, from the UK, to see just how green it really is. What I found surprised me: big roads, traffic, out of town shopping centres, Wal-Mart, McDonalds and Burger Kings. The eco-hostel where I stayed is surrounded by gated condominiums topped with razor wire and electric fences, manned by sentries.

I took an elliptical trip on one of the renowned metro-buses accessed by entering a glass tube. These fully wheelchair-accessible expresses have a different network, making fewer stops. The city was designed around this transit system, and it is this for which Curitiba is the most famous. It's afternoon, and we don't encounter a single traffic jam.

My guide - Rafael, a sustainability consultant for a local publisher - says the city is resting on its laurels. It won its reputation for sustainability in the '80s and '90s when many of the initiatives it is still renowned for were inaugurated. But now the rest of the world has caught up.

We visited SPVS, an NGO responsible for biodiversity conservation, where a director, Ricardo, explains how they audited the green areas and discovered that a City Hall claim that Curitiba had over 50 square metres per person of greenspace wasn't exactly as green as it sounded: much of it was grass verges. So they are working with the city so credit only goes to the biodiverse areas with native species. They have two projects: the 'Condominio do bioversidade' works to educate people about the native species and their value. 'Bio Cidade' aims to create officially protected areas. The City has signed up to the UN Convention on Biodiversity.

At the Free College of the Environment, the educational officer, Naiana Arruba says it was set up in 1991 by Jaime Lerner himself, to try and raise awareness and do research into environmental issues. "However," she continues, "the City stopped supporting it four years ago for political and personal reasons. Unless we can secure more sponsorship we may close."

She says the water in the lake is being polluted by a budding favela - illegal occupation = in the land above the quarry. "Cohab, the municipal housing agency, should turf them off," she says. She doesn't see it as an opportunity to demonstrate sustainability in practice. She is clearly disillusioned.

Rafael says these favelas are hidden away "on the edges of Curitiba and its commuter towns. Curitiba is a victim of its own success. As it proclaimed how 'sustainable' it was, it attracted inhabitants from everywhere, exploding from a few thousand to 1.7 million."

The favelas' inhabitants sort the rubbish. Everywhere they pull their barrows, laden with cardboard, old exhausts, abandoned white goods and plastic. There also live the women who work as cleaners and nannies in the middle clsss homes.

"Isn't this Curitiba's dirty secret?" I worried. "That it would grind to a halt if not for the existence of these second class citizens?"

Our next stop provided a kind of answer. At NGO Alliança Empreendedora, co-director Lina Useche, a beautiful 25-year old, described their work with favela women, training them in crafts, sewing and business management, obtaining micro-credit, via support from banks and Wal-Mart, and creating co-operatives to make and market their work.

"The collectors lease the barrows for $R10 a day," she said. "They can barely earn that from what they sell. So we help them obtain microcredit to buy the barrows and, by clubbing together, acquire balers to package the garbage and sell direct to the top buyer for a better price."

Lina showed us beautiful bags and wallets made from recycled materials. 97% of rubbish is recycled by the favelas. The City Hall has realised that they need to help the collectors and have just given the Co-ops responsibility for the remaining 3%.

Finally, we got a tour of a favela: a tight hodgepodge of small homes cobbled together with any materials in rubbish-strewn streets, a lively area with its own economy of shops, barbers, cafes, but most of all warehouses where the rubbish is sorted into types for selling.

Some homes have been modernised: good materials, a fresh coat of paint applied with pride. Lina said, "When people become richer, they don't leave the favelas - they improve them, and give employment to those around." The community bootstraps itself up.

But there's no trickledown. It's due to the work of NGOs and the funding from the City Hall. Cohab is charged with providing housing. "But" says Lina, "when people leave the favelas they have to pay taxes, water and energy." Why should they leave, then? Some politicians oppose helping them because it only encourages the wrong sort of people to come.

But unless the City completely changes its system of rubbish recycling they will always need the favelas. And the favelas need the rubbish to provide their income.

Water and sanitation remain a problem but the city is getting on top of it.

There are so many environmental technologies in Europe that they haven't heard of here yet, which they could be implementing instead of 'wiring in' unsustainable infrastructure and habits: sustainable urban drainage, green rooves, solar water heating, micro-renewables, trains, shutters to reduce the need for air-conditioning, and even small water-saving tricks like fitting plugs in sinks and basins.

This is what worries me most - not here but everywhere. Unsustainable bad habits are harder to undo than changing a piece of energy kit.

Whether the habit is fast food, freezers, no plugs for basins, tumble driers, or no shutters on windows, they have causal chains that result in high ecological footprints that can be locked in for decades.

Some of these habits are universal and a function of capitalism, like fast food. Others are not, but a result of planning issues, like the plugs, transport and shutters. It's the latter which we can campaign for developing cities to take aware action on.