From this story in USA Today:
_Here's what Matias Rojas Perez first saw on a trail walk in the Moapa Valley National Wildlife Refuge: a wild rabbit dashing past, a 3-inch-long endangered fish, soaring birds and creeping snakes. Here's what his doctors saw: a chance for 200-pound, 5-foot-3, 10-year-old Matias to grow healthier. Instead of an order for pills, pediatricians at the Children's Heart Center in Las Vegas have given Matias, his mother, who is diabetic, and his 9-year-old, 136-pound little brother, a "nature prescription."
_More than 100 of the 553 U.S. Fish and Wildlife Refuges such as Moapa are part of a national consortium of federal parks and the National Environmental Education Foundation now using this prescription tactic. It's funded by a $75,000 grant to improve family health through a two-year pilot project linking the federal agencies with health care providers. The aim is to turn doctors, nurses, teachers and therapists into "nature champions" who steer children and their parents into the outdoors.