São Paulo is Brazil’s largest and richest city, with a metropolitan region the size of Los Angeles or Shanghai. Its population has nearly doubled in the past 45 years, and growth in the last decade was 9.2%. As the country’s financial capital, with a constituency the size of some European countries, São Paulo plays a key role in national politics.

A continuous, dense city that spreads out into the tropical vegetation of the Tietê river valley, São Paulo’s boundaries are in a state of constant flux as it expands outwards from its emptying historic core to a disparate periphery, with poor favelas (squatter settlements) close to the exclusive highrises of the rich.

Today six million cars operate on São Paulo’s streets and a thousand new cars are registered every day. Just under half of daily journeys are by public bus, while just over half are by private car. Long commute times (four-hour journeys for residents of some outlying districts) and vehicle pollution are major issues, yet investment in other modes of public transport, such as the metro, has been minimal. The invasion and contamination of the city’s watershed by informal housing – whose poor occupants cannot access adequate and affordable housing within the existing city fabric – threatens the provision of drinking water and viability of the sewage system for the wider city region.