In Sweden, a right to nature is in the constitution and Allemansrätten, or the freedom to roam, is granted to all citizens. Swedes don't need permission to wander private lands, as long as they don't disturb or destroy anything wild along the way. There's plenty of outdoor exploration to be done, as 97 percent of Sweden is uninhabited, filled with 29 national parks and more than 4,000 nature reserves. Time outside has been proven to boost mental and physical well-being, so it should come as no surprise that Swedes are some of the happiest people on Earth—and some of the most sustainable.
In order to call attention to the health benefits of this progressive national policy, the Swedish Tourism Board joined forces with a psychologist and neuroscientists from the Karolinska Institute in Stockholm to organize a pretty epic experiment.