“Please Straddle Turtles.” The curious sign, on a lonesome dirt road that winds through marshes and forests along the northern Chesapeake Bay, shows a military Humvee taking care to keep a spotted turtle between its wheels.

The turtle in question, classified as endangered by the International Union for Conservation of Nature, is a small reptile with a dark head and shell with bright yellow polka dots, reminiscent of the starry night sky.

One wouldn’t expect it to be surviving here at Aberdeen Proving Ground, a giant military facility near its namesake town in Maryland, where every weapon a soldier fires, up to the biggest tanks and artillery, has been thundering away since the United States entered World War I a century ago this year.

But the little turtle, which can live more than a century and thrives with exceptional water quality, has been the focus of two doctoral theses conducted over the last 40 years here at APG, as the proving ground is known.

It’s a tiny illustration of how nature manages surprisingly well at a place whose main mission since 1917 has been devoted to war-making and national defense. And the nurturing of nature on the proving grounds is actually typical of millions of acres owned by the Department of Defense nationwide.

On this late September day, we’re on Carroll Island in Baltimore County, toward the proving ground's southern boundary, touring the installation from a habitat perspective. The military ownership stretches north about 15 miles through Harford County, almost to the Susquehanna River, encompassing two Bay tributaries, the Gunpowder and the Bush.

All told, APG contains around 73,000 acres of land and water and more than 100 miles of tidal Chesapeake shoreline. The vast bulk of it is undeveloped forest and wetlands, providing buffers around its mission — testing weapons, vehicles and other combat gear used by the Army. Much of the acreage is also effectively off-limits to human intrusion because of unexploded ordnance or “UXO,” the legacy of 100 years of constant gunfire.

Carroll Island lies within a 13,000-acre portion of the APG that became a federal Superfund site in 1990 because it was contaminated with residues from chemical weapons testing and manufacture dating back to the use of mustard gas in the 1920s. The 900-acre island is now remediated and dotted with military-created wetland ponds that host an array of amphibians and waterfowl.

Cleanup of contaminated soil and groundwater continues in the larger area of the proving ground’s Edgewood Peninsula. The Army’s efforts “continue to be protective of human health and the environment in the short term,” according to a recent assessment by the U.S. Environmental Protection Agency, which oversees the cleanup.

Ironically, the contamination has limited human activities and created a virtual wildlife refuge across thousands of acres. We passed a pile of coyote poop on the way to a pond in an area where rarely seen golden eagles, migrating down from Canadian nesting grounds, have been documented in winter.

Bald eagles were once almost as rare as goldens around the Chesapeake because of the widespread use of the pesticide DDT, which weakens the birds’ egg shells. The APG was one of the first places where bald eagles returned. I came here on a wintry day in the 1970s to record this for The Baltimore Sun. As cannon fire boomed nearby, several of the magnificent birds perched, unbothered, as falling snow capped up a couple of inches high on their white heads.

Nowadays, eagles are common enough on the grounds that power lines have “diverters” — twirling, flashing, glow-in-the-dark devices — to help the big raptors avoid striking the lines. The grounds this year fledged 85 young eagles from 65 active nests, the largest concentration of bald eagles in the northern Chesapeake, said Lynda Hartzell, the APG environmental protection specialist.

“All this would be townhouses and marinas and highly developed shoreline if not for our mission here,” she said.

If one doubts that, they have only to visit what was the federal government’s first choice for a place with enough acreage to test heavy artillery in 1917, when the United States entered World War I. Today it’s heavily developed Kent Island, the eastern terminus of the Bay Bridge.

The proving ground’s 113 square miles, about half land and half water, took a much different path. The region had once been the territory of the native Susquehannocks, encountered by Capt. John Smith as he mapped the region in 1608. In 1658, Nathaniel Utie established a trading post on what is now the APG’s Spesutie Island (literally ‘spes utie,’ or Utie’s hope). In 1680, the first Baltimore Town, miles north of the present city, became a bustling tobacco port on the Bush River within the proving grounds’ current boundaries. It is an important archaeological site, but UXO has hindered full examination.

In 1917, propelled by the war and three presidential proclamations by Woodrow Wilson, Aberdeen Proving Ground came into existence with lightning speed after local protests took Kent Island off the military’s wish list. Between October of that year and January of 1918, the land was acquired, local residents moved out with $100 an acre for compensation, and the Army fired its first shots — testing shells that fragmented into shrapnel.

When the military acquired the land, it had been mostly cleared, ditched and drained for agriculture, supporting five canneries. Under military use, forests have increased at least sixfold, to about 18,000 acres. Wetlands claim another 13,000 acres.

The mission that drives the installation — testing what Hartzell describes as “anything a soldier fires, wears or rides in” — occupies relatively little land. A study several years ago by Steve Getlein, a biologist with the Army Environmental Center, found that even the mechanized maneuver areas of military bases were comparable with agriculture in natural diversity and with little of the polluted runoff of fertilizers, soil and manure that make farming a major pollution source in the Chesapeake watershed.

With Todd Beser, APG Chesapeake Bay specialist, we ran at high speed by skiff out of Lauderick Creek for perhaps 20 minutes to see the historic, 1826 lighthouse the Army maintains on Pooles Island. It still lights the night, though no longer for navigation. The island’s 200 acres, part of the grounds and its Superfund site, are mostly given over to sandy beaches and woods, with large numbers of nesting ospreys and great blue herons.

The tidal shorelines, for as far as we could see on our boat trip, are sparsely developed, green with the mature forest and wetlands that would be an ideal prescription for water quality throughout the estuary. Spaced along those shorelines are picket boats, distinctively marked craft with police-style lights flashing to indicate active firing and warn civilian watercraft to keep their distance.

The long strands of translucent, olive-green vegetation washing up on the Pooles Island beach are wild celery, a favored food of Bay waterfowl. It’s one of eight species of submerged vegetation that have been making a strong comeback in APG waters — and around the Upper Chesapeake in general — in recent years.

The felicitous mix of nature and the military was a happy accident at Aberdeen and other Department of Defense installations for the first two thirds of the 20th century, largely a byproduct of the military’s need to fence human civilization out of large tracts of land.

During the 1930s and 1940s, for example, habitat loss and overhunting had caused white-tailed deer to become rare throughout most of Maryland. Meanwhile, the APG’s herd was exploding. A trap-and-relocate program centered there succeeded in jump-starting deer herds across the state.

Today, the proving ground’s deer are overpopulating again, despite a public hunt that is limited by weapons firing and UXO. A memorable “deer moment” occurred there in 2001 when the APG was honoring baseball legend and Aberdeen native Cal Ripken, Jr., by having him fire the Army’s latest and most destructive tank. As television cameras rolled, several does ambled directly downrange from the tank and began munching the grass. Reassured by military officials, and with a nervous glance at the cameras, Mr. Ripken let ’er rip. The shock waves ruffled the fur along the backs of the deer, which didn’t even look up from eating.

Deer are joined by large flocks of wild turkeys, wood ducks that have been counted in the thousands and a major resurgence of beaver.

Military bombing and shooting here, and at many other installations, also benefitted nature by restoring a crucial element to many ecosystems — frequent fires — which modern society suppresses wherever possible. On the proving grounds, fire has created open grasslands, excellent habitat for many birds.

It adds up to a paradox that extends far beyond the loud greenery of the Upper Chesapeake at the proving ground. Wherever the missions of war and defense create “no-man’s land” on military and related installations, the rest of nature often thrives.

Journals from the early colonial period around the Chesapeake remark how wildlife flourished in the buffers between American tribes. Bison made some of their last stands in lands similarly set aside between hostile Midwestern tribes in the mid-1800s.

Today, the heavily land-mined demilitarized zone between the two Koreas has become one of Asia’s most important refuges for endangered cranes. Some of Central America’s most intact rainforest lies in thick belts along the Panama Canal, preserved by U.S. Congress more than a century ago to buffer the waterway against overland invasion.

Across the nation, the U.S. military controls a total of approximately 25 million acres; in the Chesapeake watershed, it’s about a third of a million acres. Nationwide, more rare and endangered species of plants and animals occur per acre on these properties than in national parks or wildlife refuges, according to a survey by J. Douglas Ripley, who managed natural resources for the Air Force.

It’s the same story for vast, wild tracts protected since World War II around nuclear bomb-making facilities by the Department of Energy at Savannah River in Georgia and along the last undammed stretch of the Columbia River at Hanford in Washington state.

The variations in these buffered landscapes is increasing, too, because the modern military requires a diverse range of habitats in which to train, said Bob Barnes, a retired brigadier general who oversaw environmental matters at the Army’s Judge Advocate General’s Corps.

That means jungles and swamps for jungle warfare training, as well as deserts and mountains to mimic those potential battlefields. “And the military needs those landscapes to be real,” Barnes said, explaining that, when training for potential life-or-death missions, soldiers need every part of the landscape they might encounter to be present.

Starting with the Sikes Act, passed by Congress in the 1960s to encourage formal conservation on bases, the military has moved toward science-based ecosystem management that may rival or exceed that on any other government or private lands.

“Working with the natural resources people here has shattered my old preconceptions about the Army’s…dedication to protecting the Bay and its critters,” said John Leader, a visiting research participant and former community college and high school teacher who accompanied us on our day trip around the proving grounds.

A recent and hopeful chapter in the story of the military and the environment is a little-known federal program referred to as REPI, for Readiness and Environmental Protection Integration, which has helped to both expand the landscape buffer around military facilities and protect more habitat.

Both needs are real. As species like red-cockaded woodpeckers became more endangered by loss of habitat on civilian lands, military bases were becoming more burdened under the federal Endangered Species Act as they became refuges of last resort. At Fort Bragg in North Carolina, burgeoning residential and commercial development just outside the Army base led to an upsurge in complaints about military operations.

In response to situations like these, REPI in the last decade and a half has protected nearly half a million acres nationwide on nonmilitary lands. In the Chesapeake watershed, the program has contributed at least $50 million to protecting more than 31,000 acres.

At Aberdeen Proving Ground, a REPI-related program aims to mitigate the buildup of population within what some have called the base’s “sound-shed.” Noise from firing can carry across the Bay, Todd Beser said. Each morning a test shot is fired at 7:30 a.m. while a computer program is run, incorporating atmospheric conditions to indicate how far the sound will travel and how annoying the roar of guns will be.

Working with the Harford Land Trust on the Western Shore and the Eastern Shore Land Conservancy across the Bay, the APG has protected more than 200 acres from development and is working on another 800 acres, Beser said.

The U.S. Navy, which has similar concerns about more development within its noise zones from aircraft overflights and weapons testing, has contributed $17.7 million dollars under REPI to protect about 7,300 acres of land around the Potomac River and Delmarva Peninsula. The federal funds are generally matched by states and other civilian sources.

The flourishing “nature of the military” is ultimately a commentary on how much we continue to wage war on our environment in pursuing our civilian lifestyles. Perhaps it is time to recast the mission of unending economic growth and to recast the concept of national defense to include all of nature.

(As originally posted, this story misidentified John Leader. The Bay Journal regrets the error.)