Climate change is “the existential threat of our time,” Biden said, and the people he was nominating to lead the Environmental Protection Agency, the White House Council on Environmental Quality and the departments of Energy, and Interior will be “ready on day one.”

“We need a unified national response to climate change. We need to meet the moment with the urgency it demands, as we would with any national emergency, ” Biden said at an event in Wilmington, Del.

With Republicans set to hold at least 50 seats in the Senate, likely dooming the chances for sweeping climate and environmental legislation, Biden will be relying heavily on the officials to advance his clean-energy agenda through federal regulation. He has proposed a sweeping $2 trillion climate plan to promote clean energy, called for an emissions-free electric grid in 15 years and and promised to pare oil drilling on federal lands.

“We need to get to work and we’ve got to get to work right away,” Biden said.

He vowed to promote the use of electric vehicles by having the federal government purchase more of them, and to get 500,000 charging stations installed. He also called for 1.5 million energy-efficient homes and public housing units to be built, and 3.2 million abandoned oil and gas wells to be plugged.

He said the U.S. would rejoin the Paris climate accord and establish a climate-focused civilian conservation corps to put people to work.

The nominees he presented represent veteran government leaders and regulators as well as environmentalists that progressives had demanded. They include former Michigan Gov. Jennifer Granholm to lead the Energy Department, North Carolina environmental regulator Michael Regan to be EPA administrator and Democratic Rep. Deb Haaland to head the Interior Department. Biden has also tapped lawyer Brenda Mallory to be chair of the Council on Environmental Quality, Gina McCarthy as national climate adviser and Ali Zaidi as her deputy.

If confirmed, Haaland would be the first Native American in a U.S. cabinet post, Mallory would be the first African American to lead the White House Council on Environmental Quality and Regan would be the first Black man to serve as Environmental Protection Agency administrator. Lisa Jackson was the agency’s first African American administrator, under former President Barack Obama.

Neither McCarthy nor Zaidi will need Senate approval to become climate advisers, and the others are widely expected to be confirmed. However, Republicans have already signaled they will sharply scrutinize the records of Haaland and Regan, including their past opposition to fossil fuel projects. Haaland, for instance, has supported a ban on the fracking process that has propelled U.S. oil and gas production—a stance that gives oil industry leaders concern but has been heralded by environmentalists.

Senator Kevin Cramer, a Republican from oil- and coal-rich North Dakota, warned the candidates could see “a bit of a brawl,” during a Fox Business Network interview Friday.

The Independent Petroleum Association of New Mexico said Thursday it had “serious concerns” about Haaland’s nomination, adding that she “has repeatedly demonstrated contempt toward our industry.”

The Interior Department runs the national park system and oversees grazing, recreation, energy development and other activities on about a fifth of U.S. land. The department holds trust title to more than 56 million acres for tribal nations and its Bureau of Indian Affairs works directly with 578 federally recognized Native American tribes.

Read More: Republican Threatens ‘Brawl’ Over Biden’s EPA, Interior Picks

Haaland, 60, and a citizen of the Laguna Pueblo, a 7,700-member tribe west of Albuquerque, New Mexico, has drawn widespread praise from environmental groups and tribal leaders. They say she would bring a deep commitment to protect the land to an agency in charge of 500 million acres of it. She was just elected to her second term in the House of Representatives.

Appearing to fight back tears as she accepted Biden’s nomination, she noted that one prior Interior secretary had pledged to “to civilize or exterminate” American Indians.

“We will ensure that the decisions at Interior will once again be driven by science,” she said.

McCarthy, 66, who now leads the Natural Resources Defense Council, pioneered the first limits on greenhouse gas emissions from power plants during her nearly four years leading the EPA during the Obama administration.

“I’m here today because climate change is not only a threat to the planet — it is a threat to our health and our well-being,” McCarthy said. “Defeating this threat is the fight of our lifetimes and our success will require the engagement of every community, every sector in our nation and every country in the world.”

Mallory, 63, previously served as the Council on Environmental Quality’s general counsel under former President Barack Obama. Most recently, she has been the director of regulatory policy for the Southern Environmental Law Center, a group that uses litigation to promote clean air, safe water and wildlife conservation.

“It is essential that we deploy smart and humane policy to help communities pull themselves back from the edge and improve the health, security and prosperity of all people,” Mallory said.

Regan, 44, already worked at the EPA for roughly a decade, though he’s currently secretary of North Carolina’s Department of Environmental Quality. He has guided initiatives to combat environmental inequities and climate change, and he’s been at the center of disputes over new gas pipelines and pollution cleanup that are playing out nationwide.

Invoking Biden’s campaign motto to “build back better,” Regan said on Saturday that “we need an all-hands-on-deck approach from industry and individuals, finding common ground to build back better.”

Granholm, 61, served as energy adviser to Hillary Clinton’s 2016 campaign and has been credited with expanding Michigan’s clean energy industry during her two terms as governor. She served as Michigan’s attorney general from 1999 to 2003, has been an adviser to the Pew Charitable Trusts’ clean energy program and is a professor at the University of California, Berkeley.

Granholm said Saturday that the Energy Department would take steps to assure that a transition to clean energy would result in jobs for Americans.

“We can win those jobs for American workers with the right policy,” she said.

Zaidi, New York Governor Andrew Cuomo’s deputy secretary for energy and environment, is a longtime adviser to Biden who helped negotiate the Paris Climate accord. He is a native of Pakistan.