The Black Rock Desert in northwestern Nevada is the dry, alkaline bed of a long-vanished prehistoric lake known as Lahontan. A thousand square miles of flatness east of the Calico Hills and west of the Jackson Mountains, it's a great place to test supersonic cars, race gliders or launch rockets.

It's also been the site of the annual Burning Man festival since 1990. In late August, tens of thousands of people (70,000 in 2016) gather to dance, camp, party, create — and often burn — artwork, taking a weeklong respite from their regular lives. They arrive in cars, trucks and RVs, bringing generators, alcohol, tents, costumes, bicycles, showers and “art vehicles” — along with varying levels of experience with the principle of Leave No Trace.

In 1998, the Bureau of Land Management district that includes the Black Rock Desert imposed unprecedentedly strict inspection standards on the event’s permit. After it ended, the BLM sampled high-use spots and random GPS points, amounting to around 4,300 square feet. Staffers picked up every bit of “Matter Out Of Place,” or “MOOP,” in that one-tenth of an acre — all the fragments of wood, glass, plastic, sequins and feathers that were left behind. If the assembled trash covered more than a square foot, fines would be levied, and future permits might be denied.

But Burning Man met the test, and has every year since, thanks to the event’s Playa Restoration crew, which disassembles the temporary city's infrastructure, including the Trash Fence that surrounds it and catches wind-blown stuff. The crew, many of them volunteers, remove every piece of trash they can see, then form lines and comb the playa, sometimes on hands and knees, searching for tinier bits of debris.

The Burners’ thoroughness set a precedent and inspired the BLM. Why not be this strict with everyone — rocketeers, supersonic record-seekers and glider racers? “The standards that we placed on Burning Man, we now place on all activities,” says Dave Cooper, then with the BLM's Winnemucca field office.

The restoration crew’s leader, Dominic Tinio, known as DA, now creates an annual MOOP map, which allows Burners to identify the MOOPiest areas. This feedback helps Burner camps avoid future problems — maybe appointing a camp Leave No Trace officer, putting a better tarp under a gray-water evaporator, omitting glitter, or cutting wood before it’s brought to the desert.

Restoration is arduous work, but DA says there's a high return rate for the crew. “Playa restoration is the thing that is sexy about Burning Man!”