Yuma's harsh, isolated sand dunes and gravel washes, its sparse three inches of annual rainfall, its temperatures routinely topping 110 degrees, even its natural vegetation, have become assets worth preserving. That's a major perspective shift from the 1940s and '50s, when the military treated many of the West's arid open spaces as expendable - wastelands perfect for munitions and nuclear weapons testing. These days, English and his colleagues work with the testing office to confine the fireworks to already disturbed areas. They also collaborate with wildlife agencies to manage the unspoiled areas in between, maintaining them as bighorn sheep habitat and stopovers for migratory birds. "Once we utilize an area," English says, "we try to stay in that area."

Still, this military playground - home to numerous bombing ranges - is far from a pristine wilderness. In 2005, rockets exploding on the proving ground likely kindled the hot-burning King Valley Fire, which roared through 26,000 acres of the neighboring Kofa National Wildlife Refuge, consuming grass, ironwood and paloverde trees, saguaro cacti, and even flame-resistant creosote bushes.

Natural environment testing is not entirely new to the military. In fact, the proving ground was established in part because the military recognized that equipment tested only in temperate conditions on the East Coast had failed when taken to battle in North Africa and the South Pacific during World War II. Today, the military conducts its tests with laser accuracy, turning the desert into a laboratory bristling with sensors, high-speed cameras, radar and other cutting edge tools. "We can actually track a projectile all the way from the time it leaves the weapon to the time it hits the target 20 miles away," says Stullenbarger.

Testers also keep their finger on the desert's pulse with dozens of portable weather stations that record temperature, wind, solar radiation and moisture and relay information to centralized databases via 600 miles of fiber optic cable. "If you tell me when and where a test was conducted, I can tell you what the environmental conditions were," Stullenbarger adds.

This carefully controlled and monitored environment has allowed the military to tackle some of the most vexing challenges of desert combat. Crashes caused by brownouts, for example - the blinding clouds of dust stirred up by a helicopter's rotors - cost the Army roughly $100 million a year in Iraq and Afghanistan. In response, the Department of Defense commissioned Project SandBlaster and sent researchers to the proving ground to kick up their own brownouts.

While pilots hovered over Yuma's "dust range" - an area designated for dust experiments - testers took photographs and video to record the size, shape, movement and amount of time the clouds lingered under various helicopters. They also gathered samples to determine the size, density and mineral composition of the dust particles. Now, researchers are using this information to recreate specific clouds in laboratory wind tunnels and develop sensors to help pilots "see through" brownouts.

The proving ground is also an ideal place to test the mettle of Humvees and armored vehicles by literally running them into the ground until the grit, sun, heat and dry air wear them out. A test crew can put 20,000 miles on a vehicle in eight weeks. Even Yuma's 200 miles of vehicle tracks are monitored and reconditioned to standardize testing. "We want them to have the same level of severity season to season and year to year," Stullenbarger says. "If they get smooth, we rough them up. If they get too rough, we smooth them out."

Though the proving ground also maintains facilities in Alaska and Panama for testing in extreme cold and humid tropical conditions, the importance of Yuma's facilities is likely to grow as the military's combat and peacekeeping missions focus on desert regions of the Middle East, North Africa and Southwest Asia.

Ironically, the desert controlled by the military may be better protected than that immediately outside the proving grounds. "Our pace of taking over natural desert is so much slower than the civilian world," says English, who notes that the town of Yuma, 20 miles from the proving ground, is one of the fastest-growing communities in the West. Although the area disturbed by testing has grown slowly as the workload has increased, 80 percent of the proving ground still doesn't feel pressure from testing - or urban sprawl. Amid the whirring of rotors and the concussion of explosives, the military is preserving the new value it has found in this desert.

"We take our environmental testing seriously, but we take the environment even more seriously," says Stullenbarger. "We have to maintain what we have. If we don't, the mission cannot continue."

The author is a freelance writer based in Washington, D.C., and a former HCN intern.