After months of protests over the South Dakota pipeline, activists and members of the Sioux tribe saw a victory that seemed too good to be true: On Sunday, the U.S. Army announced it would seek alternative routes for the $3.8 billion pipeline.

The protest unified members of Sioux Nation, hundreds of other Native populations, clergy and supporting veteran groups to fight the routing of a pipeline under the Missouri river, which they said would contaminate water and threaten sacred lands. When the news arrived, they celebrated. Standing Rock Sioux Chairman Dave Archambault III asked everyone to return home, and fireworks lit up the night sky.

Yet amidst the celebrations, the question remains: how long will this last?

The pipeline company, Energy Transfer Partners, has dismissed the decision as a “purely political action.” The Obama Administration is considering reroutingthe pipeline, not cancelling the construction. As the administration of President-elect Donald Trump looms in the distance, environmental advocates have expressed concern for the future. “It’s pretty clear that things are going to get worse before they get better, with the advent of the Trump administration,” environmentalist Bill McKibben said in an interview with Boston Public Radio Tuesday. “We may well find ourselves right back in the fight over this pipeline, the Keystone pipeline, [and] a thousand other things.”

McKibben, hesitant to declare a full-fledged victory, applauded the unity of the group. “For the first time since the Battle of Little Big Horn, people were together in the most powerful, strictly non-violent unity, and it left, by the end, the Obama administration no choice but to uphold that kind of dignity and courage,” he said. “This was an incredibly important moment for a few reasons— maybe chief among them that it’s the biggest victory that Native Americans have won, depending on how you look at it, in the last couple hundred years on this continent. It was a remarkable Autumn in the Dakotas up there.”

According to McKibben, the Obama administration was slow to act, but added a little bit of insurance for the incoming cabinet. “Instead of just denying the permit outright, which would have let the company come right back with a new one as soon as Trump took over, they refused to grant the permit for putting the pipeline under the Missouri, and instead instituted a environmental impact statement process, which of course is what they should have done in the first place,” McKibben said. “[But there’s plenty of reason to criticize the Obama administration on this.”

President-elect Trump met with environmental activism leader Al Gore on Monday, giving hope to environmentalists who dread an administration led by a man who denies scientific evidence of climate change and hopes to dismantle the Paris agreement. According to McKibben, this meeting, which he described as “ window-dressing,” might just be one more dubiously productive scenario. “I’m glad that Al went and did it, bless his heart,” he said. “And I’m sure that he gave a remarkable talk to him, because he has been, over the last decades, the most eloquent spokesman for why we have to do something about climate change. I just dont think… perhaps I will be proved to be wrong and we will see Rachel Carson reincarnated in the figure of Ivanka Trump, and who knows… but judging on who he’s appointed, judging on how he has conducted himself, the odds that he’s going to act constructively on this issue seem small to me.”