The favelas in and around Rio de Janiero regularly suffer from mudslides and floods resulting from the combination of heavy weather and deforestation. But if the denizens of the squatter cities have few recourses for lowering the weather risk, they can do something about the trees: plant more. According to the San Francisco Chronicle, favela dwellers have planted over 4 million trees around the edges of Rio, thereby reducing the threat of mudslides and floods. But the trees have had an even greater effect than that:
In addition to saving lives, the municipal project has resulted in the return of dozens of species of birds, monkeys and other animals -- many not seen in decades. Natural springs have been reborn, air temperatures have become cooler, and mahogany, rosewood and other native species of tropical hardwood once more grow in the region.
Nearby trees have also made it possible for residents to supplement their meals with fresh fruit, and to boost the local economy by selling fruit to the rest of the city.