For the city's 7 million slum dwellers, poverty, disease and pollution go hand in hand. People who cannot afford garbage collection dump rotting trash in the streets, and those without sanitation deposit human waste in public places. Untreated sewage flows into local creeks and coastal waters, and mosquitoes and flies spread a host of illnesses throughout the densely populated shanty towns.

Thirty per cent of the world's poor live in urban centres, while the remaining 70 per cent - over one third of the world's population - live in marginal, ecologically fragile countryside across Asia, Africa and Latin America. Though specific challenges may vary, poverty exacts high human and environmental costs from both.

Most of the rural poor depend directly on limited natural resources. Desperation drives them to take what they can from the land and water, often depleting the very resources they need to survive. But they have little choice.

Special species
Madagascar is home to 150,000 plant and animal species that cannot be found anywhere else in the world. Unique birds, lemurs and chameleons inhabit the island - along with its 16 million citizens, 12.8 million of whom live on less than $2 per day. Most of the people rely on slash-and-burn methods to clear land for cash crops like rice, vanilla, coffee and sugar cane. Eighty per cent of the country's rainforests have already been destroyed.

Madagascar's government has pledged to triple the size of its national wildlife reserves from 1.7 million to 6 million hectares by the end of 2008. This seems devastating for poor people who depend on the forests for their livelihood. They recognize the long-term benefits heralded by conservationists: forests prevent soil erosion and help the land retain water and nutrients. Yet restrictions on cutting trees for firewood and burning forestland for crop cultivation leave them with few options.

Win-win solutions
Governments and citizens are increasingly solving such dilemmas by realizing that poverty alleviation can also tackle environmental degradation. Giving the poor recourse to employment, education and essential services allows them to support themselves without straining the natural environment.

Providing access to safe drinking water and basic sanitation can curb the spread of diseases like diarrhoea, cholera and malaria, and thus enable people to live more active, productive lives. In Mumbai, a volunteer association called the Community of Resource Organisations (CORO) has combined literacy campaigns with a pay-for-use lavatory scheme: it employs local youth for maintenance and educates the shanty town community about cleanliness and sanitation through simple reading material.

Keeping it green
In Madagascar, meanwhile, interested farmers receive training in low-cost, environmentally friendly techniques to maximize crop yields, and conservation groups are handing out energy-efficient stoves to reduce dependence on firewood. Jobs have opened up, including as nature guides for the island's growing ecotourism. Steady incomes have brought a new appreciation for the nation's biodiversity; at last the poor can see that they too have a vested interest in keeping Madagascar green.