SUFFOLK, Va. — The U.S. government is trying to undo the damage from two centuries of logging at the Great Dismal Swamp.

George Washington had slaves drain wetlands to harvest cedar and cypress trees from the swamp before the American Revolution. That logging continued well into the 20th Century.

Now a years-long project is under way to make the swamp wet again in the 113,000-acre national wildlife refuge in Virginia and North Carolina, where ditches dug to reach lumber dried out the peat, releasing climate-changing carbon and making wildfires more frequent.

Scientists say that when peat is in its naturally wet state, it holds onto carbon from plants that have died over the course of centuries. Dried-out peat, however, releases that carbon into the atmosphere, contributing to global warming.