National parks, such as this one at Plitvice Lakes in Croatia, are an asset because of how much users get from them Spending time outdoors is long understood to offer mental health perks, including reduced stress, improved sleep and enhanced cognition. But these public spaces might also benefit the global economy, new research suggests. Visits to national parks around the world may result in improved mental health valued at about $US6 trillion (5.4 trillion euros), according to a team of ecologists, psychologists and economists from Griffith University in Australia. "People already visit parks to recover from stress," said lead author Ralf Buckley in a press release. "In healthcare terms, it’s patient-funded therapy." But the value of such preventative therapy had never been quantified on a global scale, he noted. Through three pilot studies involving almost 20,000 people — based on a representative sample of the Australians and interviews at […]