Researchers have been studying the relationship between mental health 

and urban green space for years, but they haven't always been able to make a causal connection between the two. Now, a new study shows that moving from a less-green urban environment to a more-green one can lead to lasting positive changes in mental well-being.

A few years ago, U.S. Forest Service researchers in Portland, Oregon showed that homes with street trees sold for $7,130 more, on average, than homes without trees. And they sold more quickly. Now realtors are seeing the value of trees when renting properties. Real estate web site Rentenna.com has started tracking trees with Green Heat Maps. Neighborhoods that are "green" hot make a big difference to potential renters when they look at all the factors that create a neighborhood where they want to live.

Jessica Lopez, a four-year old with a shy smile, has suffered severe chronic asthma attacks since she was born. Her condition always worsened in the fall, when dust rose up from the abandoned fields that bordered her family's modest one-room house. Last year, city officials turned those dusty fields near Jessica's house into a gleaming park with trails, playgrounds and shaded pavilions. Then in the fall, something remarkable happened in the Lopez home: Jessica's asthma attacks did not come. It's impossible to say that the park is what turned Jessica's health around. But her mother has no doubts.

Few things rouse our appreciation for nature as much as spending every day in an office. Employees with windows that overlook vegetation report themselves much more satisfied than those with a view of other buildings and sidewalks. Workers in windowless offices tend to hang pictures "dominated by nature themes," according to one scientific survey. They also have five times greater odds of buying plants to put around their workspace, according to another. So, better productivity could be just a trip to the greenhouse away. Seriously. Office vegetation offers "micro-restoration" - the chance for our brains to recharge throughout the day.

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