As agriculture developed, and humanity became more settled, permanent towns and villages emerged, again using local materials. These settlements often showed a sophisticated sensitivity to the local environment, whether the longhouses of forest peoples in Indonesia or the Native American villages of the southwestern United States, planned with great care to make the best use of sun and shade.

But as prosperity increased, homes, towns and cities took an ever greater toll on the planet, with ecological footprints stretching well beyond their immediate surroundings. Cities suck in resources from around the world and push out pollution that affects whole regions - even the globe itself. Heating homes and other buildings is a major cause of global warming.

Meanwhile 928 million people worldwide live in unsanitary, insecure - and growing - slums: and numbers are expected to reach 2 billion by 2030. So in both industrialized and developing countries building sustainable housing for the world's 6 billion people has never been more critical.

Slum dwellers usually cannot afford even the cheapest conventionally built housing, but have shown themselves adept at building their own homes, improving them and turning their shacks into solid structures when given a chance. Site-and-services schemes can help greatly: city planners lay roads and concrete floors and - most importantly - provide clean water and sanitation drainage, allowing people to custom-build their homes on top. Such dwellings make relatively little demand on the planet's life-support systems.

If anything, the challenge of providing sustainable housing in industrialized countries, and in the wealthier areas of developing ones, is even greater. But pioneering work is being done across the globe. Here are a few examples.

photo: WWF-Brazil

The Z House, Brazil
On the outskirts of Rio de Janeiro, architect Joao Bird has designed the first prefabricated house built entirely from Amazonian hardwood certified by the Forest Stewardship Council as having come from sustainably managed forests. The Z House has many green features, from energy-saving appliances to its tiling, roofing and fencing. Even the charcoal for barbecues comes from a certified supplier.

photo: Dedetepe Farm

Dedetepe Farm, Turkey
High in the Kaz Mountains, the residents of Dedetepe Farm strive for peace through meditation and 'minimum waste through minimum consumption'. After work (the farm produces 650 kilos of organic olives and olive oil each year), they cook over open fires and at night they sleep in tents. No chemicals are used, and all electricity comes from solar panels and a small wind generator.

photo: Meredith Bowles

Black House, UK
At architect Meredith Bowles' award-winning Black House highly insulated walls, strategically oriented windows and a pump heating system make it both cost-effective and energy efficient. The Royal Institute of British Architects called it 'an exemplar… of how to design a low-cost, generous accommodation, low-energy dwelling, where every square quarter metre of floor space justifies its cost.'

photo: Ester Havlová

The House with an Umbrella, Czech Republic
This family house, built in 2003 by SEA Architects, combines traditional materials with new creative solutions based on modern technologies. Adobe masonry is covered by straw sheathing and the roof is sheltered by a waterproof cover. Traditional materials like adobe (air dried mud) are locally available, renewable and easy to recycle.

Co-housing, Canada
Started by the Danes in the 1980s, co-housing consists of small private residences, usually for some 15-35 households, clustered around a 'common house' with shared amenities including children's play areas, lounges, office space and guest rooms. It emphasizes efficient use of land, organic gardening, controlled waste and water management and energy-saving measures.

photo: www.cohousing.ca/robertscreek

photo: Mauri Rautkari/WWF-Canon

Mata de Sesimbra, Portugal
By 2014, 30,000 vacationers will be able to visit Mata de Sesimbra, the world's first integrated sustainable building, tourism, nature conservation and reforestation programme. Carried out jointly by WWF, BioRegional and Portuguese developer Pelicano, it will span 5,300 hectares of land, 4,800 of them devoted to natural reserves and forest and wetlands restoration. It aims to provide high standard, low impact One Planet Living - 100 per cent renewable energy, locally sourced cuisine, cultural celebrations and even a golf course fed by treated waste water.