Other contributing factors include the shift from rural to urban living, an increase in single-parent households or households in which both parents are employed, and a drop in multigenerational households, which leaves fewer adults around to keep an eye on kids as they explore nature.

Research has shown that free play in nature increases children's cognitive flexibility, emotional capacity, critical thinking, problem solving, creativity, use of imagination, self-esteem, and self-discipline. It makes them smarter, more cooperative, happier, and healthier. 

"Nature is the most complex, information-rich system we'll ever encounter," says Stephen Kellert, a professor of social ecology at Yale, who with the Harvard biologist E. O. Wilson helped popularize the notion of "biophilia" - the instinctive bond between human beings and other living systems. "When children or anybody interacts with nature. . . there's adaptation, response to different conditions, challenge, mastery, uncertainty, surprise," Kellert adds. Nature also increases the opportunities for kids to come together and interact. Part of becoming a critical thinker is sharing ideas with and learning from others, which teaches one that there are multiple solutions to problems. "In natural places, kids tend to play more cooperatively," says Richard Louv.

The whole article Playing It Smart! by Erica Gies, freelance environmental reporter is published here in the newsletter for Trust for Public Land.  The Trust for Public Land conserves land for people to enjoy as parks, gardens, and other natural places, ensuring livable communities for generations to come.