It’s been called the most violent spot on Fort Lewis. No other place on the 86,000-acre Army post is as heavily used for live-fire training as the post’s largest artillery impact area, or AIA, north of the Nisqually River and west of the tiny town of Roy.

The remote target zone is littered with so much old ammunition that post officials don’t allow people to set foot on the ground unless they go through unexploded ordnance training.

Even so, the 91st Division Prairie, a 7,000-acre remnant of native South Sound grasslands, is a sanctuary for four species of native creatures now so rare they may be eligible for federal Endangered Species Act protection.

Fort Lewis officials and wildlife conservationists would like to prevent that. Two years ago, the Department of Defense began paying The Nature Conservancy to help ensure the survival off-post of populations of two varieties of butterfly and a bird and a gopher. It’s called the Army Compatible Use Buffer program, or ACUB.

So far, The Nature Conservancy has received $1.5 million and could get as much as $2.2 million. All four populations have historic ties to the disappearing South Sound short-grass prairie landscape, of which the 91st Division Prairie is the largest remaining example.

Although the nonprofit conservation group coordinates the effort, much of the legwork takes place on state or Thurston County lands and is carried out by state Department of Fish and Wildlife biologists and others.

The target species are:

 • The streaked horned lark, a ground-nesting bird also sometimes found near South Sound airport runways.

 • The Mazama, or Western pocket gopher, which leaves crescent-shaped mounds of soil in its wake.

 • The Mardon skipper, a little, brown, spring butterfly.

 • The Taylor’s or whulge checkerspot, a showy, multicolored butterfly that also emerges in spring.

In 2002, the U.S. Fish & Wildlife Service designated all four as candidates for Endangered Species Act protection.

That same year, Fort Lewis adopted a dozen sustainability goals. One is to recover by 2025 all South Sound wildlife species that are either safeguarded by the Endangered Species Act or are candidates for listing.

It’s an ambitious aim, but there’s practical reason for it, said Jeff Foster, Fort Lewis installation ecologist. If the U.S. Fish & Wildlife Service decides to invoke the protections of the Endangered Species Act, it could result in extensive restrictions. That could include where and how training takes place, he said.

In the middle of the artillery impact area, the Army’s biggest explosives tear up the ground. In the lob-over areas, the no-man’s land on the edges of the target zone, the animals find refuge.

“It’s a common theme across the nation,” said Dave Clouse, Fort Lewis fish and wildlife manager.

That is one reason why Congress in 2004 first authorized the Defense Department to pay for conservation projects surrounding military installations, said retired Brig. Gen. Bob Barnes, now The Nature Conservancy’s senior adviser on Defense Department issues.

That first year, the appropriation was $12 million. In 2007, Congress provided $40 million. This year, Barnes expects $60 million.

Across the nation, about 40 bases and thousands of acres of land are involved. The Nature Conservancy oversees about half of the projects, Barnes said.

Elsewhere, Defense Department money has been used to purchase land to both protect imperiled species and insulate bases from urban sprawl.

However, The Nature Conservancy has taken a different approach at Fort Lewis, Barnes and others said. Instead of buying property suitable for species at risk, the goal is to restore and maintain lands where the creatures have historically thrived.

Locally, the program enjoys the backing of the Tahoma Audubon Society, which has a long history of conservation work on and around Fort Lewis. Executive Director Bryan Flint said it will “preserve the environment, preserve military readiness and preserve local jobs and the economy.”

The habitat restoration effort is primarily aimed at state or county-owned prairie properties in Thurston County, such as Mima Mounds and Scatter Creek Wildlife Area.

“The species just can’t be saved on Fort Lewis alone,” said Patrick Dunn, The Nature Conservancy’s South Sound program director.

LITTLE PRAIRIE LAND LEFT

Before 19th-century white settlement, the Sound South may have had as much as 150,000 acres of such prairie, extending from Lakewood and Parkland into Thurston County.

Now, only about 10 percent persists and much of it has been damaged by development or overrun by invasive species such as Scotch broom, Dunn said.

For years, The Nature Conservancy helped Fort Lewis, the state and Thurston County beat back Scotch broom and restore native grasses and flowers. Fort Lewis alone spends $100,000 annually on prairie management, said Clouse, the post’s fish and wildlife manager.

The ACUB money has stepped up efforts on multiple prairie properties outside Fort Lewis. “At the moment, the bulk of management funds are coming from the Army,” said Jeff Foster, Fort Lewis installation ecologist.

By growing native plants in nurseries, hundreds of acres of refuge lands could be transformed, Dunn said. “We’ve got to ramp up big time on seed production,” he said.

In the meantime, each of the creatures targeted for revival is a focus of basic research. Before biologists attempt to move some of the critters off the post, they are trying to find out specifically why the populations are dwindling, said Hannah Anderson, The Nature Conservancy’s rare species project manager.

The Nature Conservancy’s grant supplements other spending by the post to sustain the imperiled animals. Clouse said his annual budget provides $50,000 to support each creature.

“The over-arching goal is recovery,” he said.

REARING IN CAPTIVITY

One of the people whose job depends on the ACUB program is Mary Linders. An endangered species recovery biologist who works for the state Department of Fish and Wildlife, Linders spends about half her time on Fort Lewis, mostly focused on the Taylor’s checkerspot.

“It’s perhaps the only population left on Puget Sound right now,” Linders said.

To prevent its extinction, biologists in 2003 began to rear the butterfly in captivity.

The goal is to reintroduce the Taylor’s checkerspot to protected areas off Fort Lewis where Linders and other biologists believe it could thrive.

In the spring, Linders collects eggs from the artillery impact area and delivers them to the Oregon Zoo, where they grow into caterpillars and, eventually, metamorphose. The life cycle, from egg to butterfly, takes about a year.

There is precedent for captive rearing and relocation of butterflies such as these checkerspots. It’s been done in Britain and California, said Robert Michael Pyle, author of “The Butterflies of Cascadia,” a Pacific Northwest field guide.

“It’s a viable concept,” Pyle said. “There is one big caveat. That is that the habitat has to be ready to receive them.”

Among other things, that means the host prairies must offer the kinds of flowers the butterflies prefer. Taylor’s checkerspots, for example, utilize harsh Indian paintbrush, balsamroot, small-flowered blue-eyed Mary and sea blush, among others, Linders said.

Last year, for the first time, 11 captive-reared butterflies emerged from pupae and took flight at the Scatter Creek Wildlife Area south of Olympia. This year, Linders released 340 zoo-reared caterpillars in March, followed by 40 pupae in April, also raised at the zoo.

Although Linders recently saw 15 butterflies on a single day at the wildlife area, she believes this year’s cold spring weather may have killed many of the animals before they had an opportunity to mate.

Still, she’s confident efforts to conserve the Fort Lewis checkerspot population will move forward next year.

People lucky enough to see large numbers of them usually are dazzled by the show. The butterflies are so social, they form clouds, Linders said. “It’s definitely a spectacular thing to see.”

Susan Gordon: 253-597-8756

Taylor’s or Whulge checkerspot

Euphydryas editha taylori

A medium-sized butterfly with a wingspan less than 2.25 inches. Wings are black, orange, and white.

Favors open grasslands and oak balds.

Before its dramatic decline, the Taylor’s checkerspot was documented at more than 70 sites in British Columbia, Washington and Oregon.

Mardon skipper

Polites mardon

A small, brown and burnt orange butterfly with a fast, skipping flight. Adults are less than an inch wide, stout and hairy.

Larvae feed on Idaho fescue, a bunch grass common to South Sound prairies. Adults nectar on blue violet. Butterflies avoid Scotch broom.

The historic range and abundance of Mardon skippers is not precisely known. It has recently disappeared from four sites in the South Puget Sound area and one in the southern Washington Cascades.

Mazama or Western pocket gopher

Thomomys mazama

The only pocket gopher in Western Washington is found on the Olympic Peninsula and in the South Sound.

It’s named for its fur-lined cheek pockets or pouches.

Adults are 8 inches long, including 21/2-inch tails.

Typical pocket gophers move a ton of soil to the surface annually.

Unlike moles, they only eat vegetation and their eyes are visible. Gopher tunnels are not visible from the surface.

Streaked horned lark

Eremophila alpestris strigata

Ground-nesting birds that seek out treeless landscapes.

The total breeding population is believed to be 780, split between Oregon and Washington. Besides the South Sound, they inhabit portions of the Washington coast.

Biologists blame recent population declines in part on predators, who take eggs and nestlings.

Females typically lay about three eggs. Both parents feed insects to the young birds.