A local conservation group has purchased a large piece of the Keystone Tract in Berkeley County in efforts to preserve an ecologically important property on the edge of Francis Marion National Forest, officials said.

The Lowcountry Open Land Trust, under the name Quemby Barony LLC, last week paid $6.7 million for 1,677 acres along S.C. Highway 41 in Huger.

The property is part of the wetlands mitigation that Boeing Co. has agreed to for its planned jetmaking expansion on nearly 500 acres at Charleston International Airport.

The effort aims to meet regulatory requirements that Boeing must compensate for the need to fill 154 acres of wetlands on its expansion site.

The Keystone Tract purchase bolsters preservation efforts by the Lowcountry Open Land Trust along the Cooper River corridor. The group has helped preserve thousands of acres along the corridor, which includes property like old rice plantations and land near industries, such as Nucor Steel and BP, said Elizabeth Hagood, executive director.

"There was a big hole in the middle of the conservation area, and that's Keystone and why it is so important," she said Friday. "The good news is that this is a permanent conservation outcome for that property that has been in play and threatened for development for a long time."

Hagood said the group purchased the 1,677 acres but acted as an "engine" in Boeing's pledge to preserve a total of 3,618 acres critical to the health of the Francis Marion National Forest.

"This is one property they (Boeing) knew they wanted, and we went ahead and purchased it," Hagood said.

Other nearby properties in Boeing's preservation campaign include Fairlawn and Nebo, which have been identified as critical to thwarting development from endangering the Francis Marion's efforts to re-establish native longleaf pine ecosystems.

The airplane maker set up the reportedly $12 million deal by using the Lowcountry Open Land Trust and the Open Space Institute to negotiate for the land.

Boeing has said it will turn the acreage over to be preserved by the Forest Service, the S.C. Department of Natural Resources or a conservation organization.

The Keystone Tract, a 4,300-acre parcel surrounded on three sides by the national forest, has been a sought-after property since International Paper put it up for sale about a decade ago.

The land has been peppered with controversy amid developers' plans to build thousands of homes there. That triggered challenges from conservation and environmental groups that have said the tract is an opportunity to connect the Francis Marion to the Cooper River and preserve safe passage for wildlife between the watersheds of the Santee and lower Cooper rivers.

"We strongly support Boeing's creative approach to wetland mitigation," said Dana Beach, executive director of the Coastal Conservation League. "Not only will wetland values and functions be protected but the public will also gain additional land for recreation and enjoyment."

Beach has said the Keystone Tract is appropriately named because development there would damage the U.S. Forest Service's ability to maintain the ecosystem.

"This is truly a win-win for everyone," Beach said. "By expediting the permitting process, Boeing will be able to create additional jobs quickly. This is possible because they were willing to go above and beyond the standard regulatory formula. Boeing has once again demonstrated an extraordinary commitment to environmental quality."

The growth of homes near the forest has been seen as an issue because controlled burns are needed to maintain the health of the longleaf pine, which exists in few places.

The national forest also is home to more than 400 species of mammals, birds, amphibians and reptiles and 1,600 species of plants, including 12 types of orchids and 12 species of carnivorous plants.

Reach Tyrone Richardson at 937-5550 or twitter.com/tyrichardsonPC.