It was the kid with the rocks that finally did it for Matthew Browning.

Browning was a ranger at Mount Mitchell State Park in North Carolina, and along with the other rangers he had been trained to give a little speech to children caught picking flowers, pocketing shells, or trying to make off with rocks. He explains it like this: “You are supposed to calmly kneel down and say, ‘I saw you picking the flower. That is so pretty! Now think about what would happen if every child picked a flower.’ And then they are supposed to have this moment of guilt.”

Browning had given this little talk many times. But on this day, in August 2009, he saw another ranger deliver it to a boy at the park restaurant, about age 8, with a fist full of rocks—rocks, Browning noticed, from the gravel road. “It was gravel we bought at the local store,” Browning says. “It made me sick. The boy was crestfallen. He was so excited about coming to the park that he wanted to take a little memento back with him. More than feeling empowered or excited to protect the natural world, now he is going to associate going to state parks with getting into trouble.”

The encounter got Browning thinking. What if every kid picked a rock or a flower? Would the park really turn into a desolate wasteland? Well, he figured, it depends on the rock, on the flower. “What kids were taking was gravel and weedy yarrow. They were not rare, delicate pink lady slippers.”

Taking home small souvenirs of the woods is just the beginning of things kids can’t do in nature. In many parks and other public lands, kids are told by rangers, parents, or teachers not to leave the trail, not to climb rocks or trees, not to whack trees with sticks, not to build forts or lean-tos, not to dig holes, not to move rocks from one place to another within the park, not to yell or even talk too loudly. Are we having fun yet?

Of course, not every kid or parent knows which flowers are widespread weeds and which are endangered. There are some heavily trafficked parks where “rogue trails” are a real problem. And yes, there are some very sensitive areas where flower picking and even removal of rocks would destroy the unique beauty and diversity for which they were protected in the first place. But there are 640 million acres of public land in the United States. Surely there’s room somewhere for a few lousy forts.

There are exceptions to the “hands off” rules: Hunting, fishing, mushrooming, collecting firewood, and other activities on public lands are regulated but allowed. But not all families hunt or fish, and certainly for smaller children, these activities are unlikely to be undertaken alone. The special category of experience that Browning worries is endangered in the United States is the simple, unsupervised messing about in the woods that so many older adults remember fondly.

When Browning left Mount Mitchell, disgruntled, he began thinking of how to bring this experience back. He went to graduate school to study recreational use of natural areas. Then he heard about “nature play areas” in Europe: set-aside areas where kids could go off trail, climb trees, collect specimens, and generally leave as much trace as they wanted with minimal adult supervision. There are many informal areas as well, where local people accept kids running wild in the woods.

Here was a way to test the assertion that letting kids play how they wanted would irreparably ruin the ecosystem.

So he spent a summer in Scandinavia. “I started off emailing people all across Sweden. Have they seen signs of children playing in the woods? Forts?” When he got wind of a natural play area, he hopped a train to the site with a GPS and a standardized form, collecting data on the damage wrought by unsupervised children. He was based in Uppsala, and by the end of the summer he just ended up walking to local elementary schools because “they all had plenty of forest and plenty of kids playing in the woods.”

His data, crunched and statistically analyzed, show that yes, kids beat up the woods. They break tree limbs, they make lots of trails, they compact the soil into hardpan where nothing can grow. But after millions of kid-hours of use by children gleefully doing their worst, these play zones remain functioning natural areas. The damage wrought by kids was comparable to that from hiking or camping. “It is not like the trees had no limbs left,” he says. “It is not like there was no vegetation.”

And to Browning, now a graduate student at Virginia Tech, the effects of play are a small price to pay to let kids really enjoy themselves, to have that irreplaceable pleasure and to create memories that will come back to them as they consider whether to vote for a conservation measure. (Never mind the more general benefits of playing in a space that isn’t boringly sanitized.)

“Every park needs to have one of these areas,” he says.

Browning imagines this shift as even more than the creation of roped-off venues for independent childhood experience with nature. He imagines rangers trusting visitors with a message a bit more complex than a blanket “Don’t touch!” Imagine a prominent sign or a notice on park maps that would give kids and parents a little context, he says: “Here are some really common flowers that we don’t want in our park. Your kids can pick bouquets of these. Here are some pine cones that you can collect in the park.”

Richard Louv, author of Last Child in the Woods, agrees that parks should make room for kids to play. “If kids don’t have some kind of connection to nature that is hands-on and independent, then they are probably not going to develop the love of nature and vote for parks and the preservation of endangered species,” he says. “Unless you know something you are unlikely to love it.”

There’s some research to back up this intuition. One 2010 study in the journal Children, Youth and Environments found that among people who ended up dedicated to nature and conservation, most had a childhood filled with unstructured play in nature, some of which “was not environmentally sensitive by adult standards; rather, it included manipulation of the environment through war games, fort building, role playing of stories in popular children’s adventure books and movies, and the like.”

Browning didn’t talk to the kids in the play areas he studied very much, but at one school he had an interaction with a boy of about 12 that stuck with him. “He was talking about how he would break branches and build forts and throw rocks. He had a knife with him. He said ‘I carve sticks into spears and stuff like that.’ ”

But when asked if he would ever stick his knife into a living tree, the boy looked horrified, “No!” he said. “It would hurt the tree; it would hurt the tree just like it would hurt me.”

“This is the ethic we are trying to teach!” cries Browning. No glum fealty to prohibitions here, no self-abnegation codified as “leave no trace”—but an active relationship with nature and clear empathy with other living things.

Browning says he knows this is a better ethic, a better way to build adults who care about nature, because he was that kid with the knife. Born in 1983, he had the kind of childhood that few people his age had, on 20 acres of woodland in southeast Iowa. “I would go out and be back by bedtime. I didn’t realize whose land I was on. I would go miles when I was 10, just hopping over cow fences.” And he left plenty of trace: “I remember running along deer trails and pretending I was a deer. I ran around with elderberry shrubs and beat on things, slid down banks, putting sediment into the river.” Yet, there were things you did not do. You did not nail into big old trees. You took care of it so you could keep having fun in it, because it was a friend.

Charlie Peek, spokesperson for the North Carolina Division of Parks and Recreation, says that Mount Mitchell and other state parks try to strike a balance between safety, protection of the park, and letting people explore and engage. But children aren’t really the problem, he says. “We have more of a problem of habitat destruction and bushwacking with adults. The kids are a little bit more timid.”

Of all the many flavors of public lands, the National Parks Service has the most hands-off rules and culture. And for good reason: They enclose some of our most fragile and beloved places. They also have the most visitors: more than 273 million a year on their 80 million acres, compared to some 160 million visitors to National Forest or 58,000 to Bureau of Land Management land. For many families, the annual vacation to a national park is the primary contact they have with nature. Even if national parks are far more crowded than other natural areas, 80 million acres is still 80 million acres. I’m not suggesting we let kids skateboard on the arches at Arches. But creating an appropriately sized and sited play area, far away from the most sublime views or historical spots, would be as cheap as a few signs and the odd marker delineating the boundaries. And for that tiny cost, a difference could be made in millions of children’s lives.

Kathy Kupper, spokeswoman for the National Park Service, says that as of now, there are no “off trail” play areas. “It is when people go off trail that people end up getting lost, or in trouble, or hurting nature,” she says. “We advocate getting kids out to parks and exploring but definitely advocate leave no trace and leaving it untouched for others.”

But when pressed about her own childhood, the experiences that presumably led to her 20-year career as a ranger and subsequent gig as press officer for the National Park Service, she remembered lots of adventures off trail. “We had forts—both boys and girls’ forts and tree swings across the creek.” Try to put a creek swing anywhere in a National park, and, Kupper says, and it will be taken down. “For safety plus for helping the tree.”

Who, though, will help the tree when all the kids who built forts in the woods are dead and the people who vote spent their little time outdoors only on the trail, hands jammed in pockets, leaving the woods untouched and unloved?