Gina Peltier prayed over the Mississippi River earlier this month, hoping that President Biden would step in to stop the oil pipeline that she says will threaten Minnesota lakes, wild-rice waters and treaty-protected tribal land.

Now, in the nation’s capital, she was joining more than 100 people in chanting for his administration to cancel the federal permit that allowed this “black snake” of a pipeline expansion called Line 3.

The climate activists protesting the pipeline outside the White House were part of a larger movement of environmental activists demanding more from the Biden administration and Democrats in Congress.

There is a rising frustration among many of those organizers, who say they helped turn out the vote in 2020 but are not seeing climate pledges translate into meaningful changes. They are worried that the opportunity to push through ambitious climate legislation will soon be gone — and that they may not have another chance.

“He said he was the climate president,” Peltier — an Anishinaabe citizen of the Turtle Mountain Band of Chippewa and a member of the Indigenous environmental justice organization Honor the Earth — said outside the White House on Monday. “Now he doesn’t care.”

Many climate activists have described an escalating sense of urgency to implement the sweeping changes needed to slow Earth’s warming, highlighted by the recent landmark report from the Intergovernmental Panel on Climate Change. U.N. Secretary General António Guterres called the report a “code red for humanity.”

The pace of emissions shows the planet is on track to warm more than two degrees Celsius above preindustrial levels, which could trigger irreversible damage, according to the IPCC report. The Greenland ice sheet could collapse, and sea levels could rise more than six feet. There will be more of the climate-fed fires of this summer, deadly heat waves and devastating floods.

Natalie Mebane read the IPCC report and thought of how much ground the climate movement in this country lost under President Donald Trump, whose administration allowed more pollution and weakened protections for wildlife.

She worries Republicans will regain power in the 2022 midterms and thinks the slim window from now until then may be the final opportunity to see climate priorities passed through Congress. If not, it could be years before Democrats are in control — wasted time that Mebane fears could cause permanent devastation.

Democrats are moving forward on their fall legislative agenda, with some in the party pushing for climate crisis measures as part of two key bills. (Blair Guild/The Washington Post)

“If the Democrats lose a single seat in the Senate, it’s over,” said Mebane, the associate director of U.S. policy for 350.org, an international climate group. “These years that we have right now is the last time that we can even make an impact and influence on climate change before it becomes runaway climate change that we have zero control over.”

Biden has tackled greenhouse-gas emissions by proposing new federal goals and mandates to begin shifting the country toward electric cars, rejoined the Paris climate accord and revoked a federal permit for the Keystone XL oil pipeline.

But activists point out Biden is still supporting Line 3, a tar-sands oil-pipeline expansion project that will be able to carry 760,000 barrels a day from Canada across northern Minnesota and into Wisconsin. They have called for him to revoke the permit, as he did with Keystone XL, and have protested for months, including on construction sites, chaining themselves to equipment and risking arrest.

The White House did not respond to a request for comment.

Earlier this month, the Senate approved the $1.2 trillion infrastructure bill with funding to tackle climate change, but many activists said the legislation has fallen short of dramatically addressing goals as lofty as this crisis demands.

That does not mean Democrats should pass just any climate legislation, activists say — it has to include the right policies. Compromising on climate, they said, is not good enough.

Though the bipartisan infrastructure bill apportions billions of dollars toward funding new public transit and electric-car charging stations, measures that are meant to cut climate-warming emissions, environmental organizations say it does not go far enough. They want to see legislation supporting Biden’s stated goal of replacing 100 percent of lead pipes and the replacement of all diesel school buses with clean electric ones.

“It’s hard to square the scale of the problem with the solutions being discussed,” said Lukas Ross, program manager for the Climate and Energy Justice program at Friends of the Earth, another environmental group. “This is not the moment to bargain away the store in the name of passing anything.”

Climate groups are focusing on the passage of a second bill through budget reconciliation, a process that would allow Democrats to pass more dramatic climate legislation without Republican support. Democrats in Congress are hoping to work in a clean-energy standard that would compel power providers to shift to wind, solar and other low-emission sources of energy to achieve 80 percent clean electricity by the end of the decade.

“Disaster has descended upon us in the form of fires, floods and storms,” said John Paul Mejia, a 19-year-old spokesman for the youth-led Sunrise Movement who is attending American University this fall. “If we don’t move at the scale that science and justice demand, it won’t look good going forward.”

Paul Bledsoe, a former Clinton White House climate adviser now leading the climate and energy program at the Progressive Policy Institute, a center-left think tank, has a more optimistic outlook than further-left activists.

“I recognize that the hour is late — there’s no question about it — but the scope of the Biden economic and clean-energy proposals is unprecedented,” Bledsoe said. And if Congress passes the bipartisan infrastructure bill and the reconciliation bill, he said, “this will be the biggest turning point in not just the U.S. but global climate history.”

The Sierra Club, one of the country’s most influential and oldest environmental organizations, wants to see the reconciliation package reflect its priorities, including achieving 100 percent clean energy, ending fossil-fuel subsidies and cleaning up abandoned mines and wells.

Ben Beachy, director of the Sierra Club’s Living Economy Program, said the country elected Biden on a bold climate platform and now it is up to Congress to fully fund these priorities.

The Sierra Club and other organizations across the climate movement, Beachy said, are “using all the tools in the toolbox” to call for these historic investments. In addition to this “full-court press” on lobbying, the organization said there have been more than 500 events, including door-to-door canvassing, over the August recess this month by various groups to demand Congress act boldly on climate investments and create a future in which the country is powered by clean energy.

“This is a once-in-a-generation opportunity to invest at the scale of the crises we face: climate change, economic insecurity and structural injustice,” Beachy said. “We have not seen this opportunity since the New Deal, and it’s critical that we seize it for our own sake and that of our children.”

Michael Greenberg, 27, of D.C.'s Mount Pleasant neighborhood was one of the climate protesters Monday.

He was arrested earlier this summer for protesting the Line 3 pipeline in Minnesota and had marched with climate-justice protesters to Lafayette Square.

During the 2020 presidential election, he spent a month knocking on doors in the Phoenix area, urging voters in the crucial swing state to cast their ballot for Biden. Now, he’s protesting the administration, saying he feels betrayed.

On Monday night, Greenberg marched with ShutDownDC to the Chevy Chase home of Biden’s chief of staff. He was later arrested with about two dozen other protesters blocking the road.

The group was prepared to camp out with sleeping bags to spotlight the climate issue, arguing there is no excuse for a carbon-producing fossil-fuel project such as the Line 3 pipeline at a time when scientists say the world needs to severely cut greenhouse-gas emissions.

“Biden has been failing us on climate,” Greenberg said, adding, “This might literally be our last chance.”