Upon acquiring the leases, the Trust for Public Land intends to turn them over to the federal government to permanently retire them.
"This story represents a respect for the valid lease rights and a respect and recognition of the value of conservation," Gov. Matt Mead said at the news conference. "What this is, is a local idea, a local passion, that created a Wyoming cure."
Mead's predecessor, Gov. Dave Freudenthal, was there, as was Susan Thomas, widow of Sen. Craig Thomas, who authored the Wyoming Range Legacy Act before his death in 2007.
Citizens for the Wyoming Range, which opposed the gas project, endorsed the deal.
"We always felt like a lease buyout was the cleanest, and a win-win, solution. It's a Wyoming solution to a Wyoming problem," group spokesman Dan Smitherman told The Associated Press.
Low natural gas prices played a role in the agreement. Rusch said PXP has been shifting away from low-margin natural gas toward higher priced oil in recent years.
The company could have completed the project in an "environmentally sensitive manner," but the trust's interest was advantageous to everybody involved, he said.
The deal should encourage owners of a handful of much smaller leases within the Wyoming Range Legacy Act territory to sell or donate, Love told AP by phone.
"I think the belief is that if you can buy out PXP, you're essentially taking away the economic incentive for these other, smaller leases to kind of tag on," she said. "Because the infrastructure costs are pretty big."
The trust has played a key role in other major land conservation deals, including protections for more than 600,000 acres in the Northern Rockies, according to Love.
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