Home to more than 21 million people, the Mexico City metropolitan area sprawls across some 7 850 sq km, forming one of the world’s largest urban agglomerations. At its heart is the Federal District – Mexico City proper – with an area of 1 480 sq km and a population of 9.4 million. The Federal District covers just 0.1 percent of the national territory, and more than half of it is, at least on paper, protected from urbanization. Known as the suelo de conservación, the protected area was created in 1992 to safeguard its vital ecosystem services, such as the city’s supply of drinking water and oxygen, and includes forests, grasslands, wetlands and 300 sq km of farmland. But residential land is increasingly scarce in the urban zone, and almost 30 percent of the Federal District’s population live in poverty owing mainly to the lack of health services and basic housing. As a result, the suelo de conservación is under constant pressure: at last count, more than 850 informal settlements had been built there and, by one estimate, its natural habitat is being lost at the rate of 600 ha a year. To prevent further degradation of the conservation zone, the Federal District’s government is promoting sustainable, ecosystem-based agriculture in rural areas and food production in the city itself.