More and more research is defining just how beneficial green spaces can be for human health, especially when woven into urban environments. Now, a new study specifically looks into how the green spaces planned for Barcelona, Spain could benefit the city. The findings show potential improvements in mental health for more than 30,000 people. According to the study authors, at least 30% of the "global burden of disease" is linked to mental health disorders. "What we found was that -- even though we're only increasing the green space by about 5 or 6% -- you get quite a considerable reduction in the number of cases of mental health problems," Mark Nieuwenhuijsen, co-author of the paper said.