Roughly 1.5 million acres of state forests in Pennsylvania lie on the Marcellus shale formation, an area rich in natural gas.
Shale gas deposits locked in the Appalachian Basin yielded 100 million cubic feet of natural gas in 2009. Environmental groups say the process that releases gas from shale deposits causes irreparable damage to the environment, however.
"Drilling companies' rush to grab private lands across the state has left few areas untouched by this widespread industrial activity," Pennsylvania Gov. Ed Rendell said in a statement. "We need to protect our unleased public lands from this rush because they are the most significant tracts of undisturbed forest remaining in the state."
Rendell said a federal study found that granting more gas leases in his state would endanger the environmental well being of the $6 billion forest products industry in Pennsylvania.
The governor said his executive order was necessary after state legislatures failed to take similar measures.
"We simply cannot risk subjecting these sensitive and high-value tracts to the same kind of environmental accidents and mishaps that have happened on private lands elsewhere in the state because of the drilling industry's poor practices," he added.