Caribou graze on the coastal plain of the Arctic National Wildlife Refuge, with the Brooks Range as a backdrop. (U.S. Fish & Wildlife Service)

The Senate rejected an amendment Thursday that sought to block a key panel from raising revenue through drilling in Alaska’s Arctic National Wildlife Refuge, a move that could make it easier for future oil and gas drilling to take place there.

Sen. Maria Cantwell (Wash.), the top Democrat on the Energy and Natural Resources Committee, offered a budget amendment that would have removed instructions to the panel to raise an additional $1 billion through federal leasing. It failed 48 to 52 on a largely party-line vote, with only Sen. Susan Collins (R-Maine) and Joe Manchin (W.Va.) breaking ranks. Collins voted in favor of Cantwell’s amendment, while Manchin opposed it.

The vote, which came before the Senate approved Republicans’ proposed budget, represented a victory for the GOP and a defeat for environmentalists. The Trump administration is quietly moving to spur energy exploration in the refuge for the first time in more than 30 years by considering whether to allow seismic testing there, but only Congress can determine whether oil and gas drilling can take place within its 19.6 million acres.

Sen. Lisa Murkowski (R-Alaska), who chairs the Energy and Natural Resources Committee, told her colleagues that they should view the budget instructions “as an opportunity to do something constructive for the country.”

“It’s about jobs, and job creation. It’s about wealth and wealth creation,” she said, adding that drilling in the refuge is “not the only option” for how her panel could find $1 billion in new revenue. “But I will tell you it is the best option, and it’s on the table.”

Opponents of the plan say that such operations could imperil the refuge’s wildlife, which include polar bears as well as caribou and migrating waterfowl. David Yarnold, CEO of the National Audubon Society, said in a recent interview that based on recent lease sales, the federal government would likely get only $9 million in revenue if it auctioned off the right to drill on the refuge’s coastal plain.

“It’s just bad math,” Yarnold said, adding that when lawmakers predict this activity could raise $1 billion, “there’s no reason to believe that that’s going to happen.”

But Sen. Dan Sullivan (R-Alaska) hailed the move as a sign that his state was inching closer to developing an area that’s been shut off from development for years.

“This resolution is another key step that we’ve recently accomplished in a decades-long fight to allow Alaskans to produce energy in our state – something that Alaskans, Democrats, Republicans, independents, overwhelmingly support,” Sullivan said in a statement. “More American energy production means more good-paying jobs, increased economic growth, and a stronger national security.”

Environmentalists said they would continue to fight any move to drill in the refuge, which has been subject to fights in Congress for years.

“Today’s vote is a wakeup call for all Americans. Americans have fought for decades to protect this last remaining truly wild landscape, and are rallying today because they believe in taking action on climate change and want to defend the rights of the Native Gwich’in people,” said Adam Kolton, executive director of the Alaska Wilderness League, in a statement. “Every member of Congress who supported this scheme, to hijack the budget process to do the bidding of oil companies, needs to hear loud and clear that we are determined to defend ‘America’s Serengeti.’”