In Rio de Janeiro, a gray-green river running thick with waste is flanked by the squatter settlement of Mandela on one side and the ornate turrets of the national public health ministry on the other. Kids paddle on hoods of cars and swim in the murky water, which the state environmental service condemned as having "pathological contamination" from sewage.
Local pastor Antônio Carlos Costa says there is nowhere else for kids to play, though he pleads with them not to swim in "Copacalama," as the kids mockingly call their muddy Copacabana. "God protect these young people," he says.
As Brazil prepares to host the Rio+20 sustainability conference this month – the third United Nations-sponsored global conference on sustainability in 20 years – its own rapid urbanization highlights the health and infrastructure challenges of promoting sustainable cities worldwide. The population of Brazilians living in cities nearly doubled between 1960 and 2010, with 84 percent living in cities, according to the most recent census.
Representatives from more than 180 nations will gather here to discuss and, they hope, target solutions for the pressing problems of a burgeoning number of megacities, from ad hoc sanitation to unemployment.
For the approximately 50 percent of the world population that lives in urban areas today, conferences like this one can seem like so much meaningless chatter. But past gatherings have yielded some hope: 189 countries agreed on the 2015 Millennium Development Goals, for example, which have seen progress in reducing hunger and boosting access to education.
"People around the world are tired of hearing about these conferences where people get together and talk and point fingers," says Seth Schultz, director of research for the C40 Climate Leadership Group. Mr. Schultz is "very excited about participating in Rio," however, which he sees as a moment to share successful models.
At the first Earth Summit in Rio, in 1992, world leaders agreed on a blueprint to rethink economic growth, emphasizing environment and social welfare. Today, again, the focus is on a more sustainable model of development for megacities – though some participants are worried about significant divides over how to do that. "[T]he risk of us not reaching significant accords that indeed change things is real," Achim Steiner, executive director of the UN Environment Program, told the local news media. "The conference and its themes are very ambitious. Will the result be ambitious?"