Although southern Dorchester County is one of the fastest-growing areas in the state, there is one big patch of land in the middle of the county that will never see a subdivision or a strip mall.

Norfolk Southern has donated a conservation easement to the Lowcountry Open Land Trust that will protect nearly 12,500 acres of the Brosnan Forest from development. Forever.

Land trust officials say it is likely the largest single easement granted in state history.

Lewis Hay, director of land protection for the land trust, said the easement is a major environmental coup for South Carolina. Hay said Norfolk Southern had the idea to conserve the land and has been quite literally driving this train.

"They've had their hearts in the right place from the start," Hay said. "They wanted the easement to be absolutely pristine."

The deal is simple. Norfolk Southern still owns the land and has the right to use it for recreational purposes (there is a corporate retreat nearby) and to harvest some timber, but gives up the right to develop it. By granting a conservation easement to the Lowcountry Open Land Trust, a nonprofit conservation organization dedicated to preserving natural and rural land along the South Carolina coast, the company has basically said the land can't be built on, even if it's sold.

It is, most local environmentalists say, a huge deal, and it's an even bigger tract. The 12,488-acre chunk of the Brosnan Forest being preserved is larger than the Charleston peninsula and nearly as large as the nearby Francis Beidler Forest, which is owned and operated by the National Audubon Society.

Norfolk Southern and its predecessor companies have owned the land for 160 years — a lush forest of long-leaf pine and a habitat for the endangered red-cockaded woodpecker.

"We recognized that Brosnan Forest is a unique property teeming with biodiversity in the heart of a significant ecological environment," said Blair Wimbush, vice president of real estate and corporate sustainability officer at Norfolk Southern. "We wanted to ensure that we could preserve the long-term health of this irreplaceable natural resource, so we began looking for the right partner to be stewards of the land, and we chose the Lowcountry Open Land Trust."

Gov. Mark Sanford called it "incredibly significant from an ecological standpoint," and conservationists also had high praise for the railroad. "It's not often we see that kind of environmental stewardship from a corporation," said Nancy Vinson, program director for the Coastal Conservation League. "They have set the bar higher for corporate America."

Hay said the significance of the easement is two-fold: It protects the natural environment for animals, both native and migratory, as well as the ACE Basin watershed. Every time it rains, the pristine forest replenishes the water table with pure, clean water. Rain trickling through the forest, environmentalists will tell you, is much cleaner than water that has sifted through some parking lot.

Will Haynie, executive director of the land trust, called the easement "one of the finest acts of corporate citizenship in the history of our state." And Larry Hargett, chairman of the Dorchester County Council, said this will help the county protect some of its land from development.

"It's all about preserving a beautiful tract of land," he said. "I think this helps us a lot."

Reach Brian Hicks at 937-5561 or bhicks@postandcourier.com