Thousands of acres of woodlands adjacent to a historic Charleston landmark have gained another layer of protection in a first-of-its-kind project in the United States.

More than 3,700 wooded acres of the 5,800-acre Middleton Place plantation forestlands west of S.C. Highway 61 have been awarded carbon credits to limit the amount of trees cut on the property and help California industries.

If the more than 250,000 credits issued were sold at once, they would generate more than $2 million for the Middleton Place woodlands, a separate entity from the tourist attraction across the street along the Ashley River, said Colby Hollifield, Middleton’s woodlands manager.

The property, already under a conservation easement to protect it from development, can now sell carbon credits from its protected forestland to California companies that exceed their carbon emission limits.

Middleton will still be allowed to exercise forest management, but it cannot exceed a predetermined amount of cutting to qualify for the carbon credit program, Hollifield said.

It’s the first project of its kind in the United States, according to Green Assets Inc., a forest carbon offset developer based in Wilmington, N.C., that is handling the Middleton project.

“Green Assets is truly honored to partner with Middleton in designing and implementing this historic project,” said Chris Newton, CEO of Green Assets. “We’re proud to be the first company to earn this designation from the state of California, and we look forward to helping other landowners across the country realize the economic and environmental benefits that the ARB program offers.”

Avoided conversion, as this type of conservation is called, prevents forestland from being converted to nonforestland use by dedicating the property to continuous forest cover.

The initial number of credits issued to Middleton by the California Air Resources Board amounts to 250,342 carbon credits. That’s enough to offset the annual electricity use of more than 60 percent of the households in the city of Charleston, according to Green Assets.

The credits can be held like stocks and sold when necessary, Hollifield said.

California allows allowances and offsets for carbon emissions. The Middleton credits will be used for offsets. Allowances are currently selling for $12 to $13 each, Hollifield said. Offsets sell for about 20 percent to 25 percent less than allowances.

“The positive economic impact ensures that future generations will have an income stream from the property while allowing us to fulfill our mission of environmental sustainability and historic preservation,” said June Duell, part owner of the Middleton forestland.

Reach Warren L. Wise at 937-5524 or twitter.com/warrenlancewise.