About 5,000 oil and gas wells sit on national wildlife refuges — some of the prettiest land that American taxpayers own — and more than a thousand of them are spewing oil and brine because regulations written a half-century ago don’t force owners to plug leaks that are harmful to animals.

On Thursday, the Obama administration moved to rectify that by reworking the old rules to strengthen regulation. If approved early next year, the proposal would require oil and gas companies seeking to drill in refuges to obtain a U.S. Fish and Wildlife Service permit before altering their operation in any way. Future projects would have to comply with stricter government rules that would force companies to remove rusting equipment, plug leaks and generally proceed in ways that do not disturb any number of creatures in marshy habitats, including waterfowl, otters and beavers.

The proposed revisions would not stop the extraction of oil and gas but would require close adherence to best management practices, particularly when it comes to hauling away abandoned pumps, tanks and debris, said Fish and Wildlife Director Dan Ashe. They “strike an appropriate balance between the rights of owners to develop energy resources with the service’s critical role in protecting refuges and the fish and wildlife that depend upon them.”

In its proposal, Fish and Wildlife noted a “legacy of orphaned wells,” which includes “an estimated 450 unplugged wells and unrestored sites that no longer have a known or solvent operator.” Removing abandoned and leaky equipment at those locations could cost taxpayers more than $20 million, the agency said.

Ashe called refuges “national treasures” where Americans fish, hunt, hike, boat and enjoy being outdoors. “We owe it to this and future generations to meet our mission responsibility,” he said.

More than 560 federal refuges and 38 wetland management areas, covering 150 million acres across the country, are under the agency’s jurisdiction. In many, the federal government only controls the surface. Private owners from whom the government purchased the land continue to hold mineral rights to resources below ground and convey those rights to drillers and miners under lease agreements. Owners include individual citizens, families and native tribes.

When drilling operations started years ago, federal officials paid little attention to how they could potentially impact the nesting grounds, mating areas and bird migration pit stops that refuges were created to protect.

According to the agency, a well blowout seven decades ago at a refuge in Texas continues to leak saltwater that could contaminate groundwater during a drought. And an invasive plant species was introduced to another refuge in the Lower Rio Grande Valley by oil and gas development, increasing the risk of wildfire. In North Dakota, brine spills at the Norman Lake Waterfowl Production Area are causing long-term damage to critical habitat for millions of waterfowl and other aquatic birds.”

Storage tanks with open tops, uncovered containers at old wells and fluid that seeps out of equipment “attract and entrap birds and other wildlife,” the agency said.

The proposed rules are set to be published in the Federal Register on Friday, and a tw0-month public comment period will follow. Fish and Wildlife plans to issue final rules by the spring.