On Thursday, the Environmental Protection Agency announced plans to loosen regulations on methane, a potent greenhouse gas known to propel climate change.

The EPA, which is part of the Trump Administration, said in a press release that it intends to loosen Obama-era national standards on the extraction of oil and natural gas, which had been implemented to limit methane from leaking into the atmosphere.

“EPA’s proposal delivers on President Trump’s executive order and removes unnecessary and duplicative regulatory burdens from the oil and gas industry,” EPA Administrator Andrew Wheeler said in the statement.

The EPA also said it would challenge the legal footing the federal government has used to regulate methane as a pollutant.

Environmental groups have decried the move, and even powerful oil and gas companies including Shell have previously urged the Trump Administration to not rollback regulations.

Where does methane come from?

Methane is a powerful greenhouse gas that is produced both naturally and by a range of industrial and human activities, explains Michael Mann, a professor of atmospheric science at Penn State.

He says the degree of methane that’s produced by natural sources — like swamps or sheep or cows — is usually “more or less balanced,” because the natural methane that’s produced oxidizes in the atmosphere and breaks down.

But over the past decade, Mann says the amount of methane in the atmosphere has increased. According to NASA, the concentration of methane in the atmosphere has risen by about 25 teragrams per year since 2006.

A 2016 study found that methane levels were reaching the highest levels in at least two decades.

“We’re upsetting the balance now, it’s increasing,” he explains. “We’re adding methane to the atmosphere faster than those processes can take it out.”

Mann says that the two primary contributors to the “pretty dramatic uptick” of methane in the atmosphere have been hydraulic fracturing — also known as fracking — and the increasing amount of livestock-raised dairy and meat consumption.

Ruminant animals, such as cows and sheep, have digestive systems different than humans that naturally emit methane, explains William Ruddiman, a professor emeritus of environmental sciences at the University of Virginia. An increasing number of cows and sheep have led to an increase in methane.

Fracking, a technique used by oil and gas companies to access subsurface oil and natural gas deposits known as shale formations, entails breaking up rock and injecting liquid to allow the oil and gas that’s trapped underneath to be released. Methane is a valuable product captured in that process.

“But they don’t capture all that methane. Some of it makes its way into the atmosphere,” Mann says.

What impact does methane gas have on the environment?

Methane is the second-most powerful greenhouse gas after carbon dioxide, explains Ruddiman.

According to Mann, while it’s less abundant than carbon dioxide, it’s much more potent when it comes to trapping heat.

On a time scale of 20 years, methane is more than 80 times as powerful as the same amount of carbon dioxide, David Doniger, the senior strategic director for the climate and clean energy program at the advocacy non-profit the Natural Resources Defense Council (NRDC), tells TIME.

However, methane doesn’t stay in the atmosphere for nearly as long as carbon dioxide.

“A century down the road … the methane we’re all producing right now, that’ll all be gone. Methane tends to disappear on a time scale of a decade or so,” Mann says. Much of the carbon dioxide humans put into the atmosphere, on the other hand, will be there for more than 1,000 years, he says.

However, Mann urges, “If we are to really tackle the climate crisis, we’re going to need to get both carbon dioxide and methane under control.”

Why is the Trump Administration reversing limits on methane gas?

The Trump Administration’s plan would loosen restrictions imposed by the Obama Administration on the extraction of oil and natural gas, which attempted to limit methane and other hyrdocarbons from leaking during transfer and storage.

The Obama-era regulation, issued in 2016, imposed the rules on any new operations extracting natural gas in the United States, Doniger explains. He says it also legally obligated the EPA to impose those same rules on already-existing operations, which make up the majority of the oil and gas operations in the country.

In Thursday’s statement announcing the rollback, the EPA sold the change as a cost-saving measure. “The proposal would remove regulatory duplication and save the industry millions of dollars in compliance costs each year – while maintaining health and environmental regulations on oil and gas sources that the agency considers appropriate.” It estimated that the proposal would save the oil and natural gas industry $97 to $123 million between 2019 and 2025.

The statement points to other existing regulation that limit the leaking of volatile organic compounds (VOCs) — or compounds that easily turn into vapor or gas — that are still in effect, and argues those regulations would protect against methane.

Doniger says that while it’s true there are other regulations in place, he says they only effect new operations, and would not impact existing ones. “So they’d be giving the new sources a rollback, and the existing sources a free pass against the obligations that currently is there but hasn’t been fulfilled.”

How are people reacting to the rollback?

The decision was swiftly denounced by environmental activists and others concerned about climate change.

“This reckless rollback pours fuel on the flames of a world on fire,” Kassie Siegel, director of the Center for Biological Diversity’s Climate Law Institute, said in a statement.

California Attorney General Xavier Becerra hinted at legal action: “We’re ready to fight this senseless decision by the EPA.”

The NRDC’s Doniger also said in a statement that “if EPA moves forward with this reckless and sinister proposal, we will see them in court.”

The oil and gas industry has historically been split on methane regulation — many smaller companies lobbied for them, while some larger companies publicly supported more government regulation, citing climate change.

In March, BP America President Susan Dio wrote in an op-ed in the Houston Chronicle that regulating methane “is the right thing to do for the planet.” She also called methane leaks the industry’s “Achilles heel.”

In a statement in September, Shell announced plans to limit its methane emissions, and ExxonMobil reportedly asked the EPA to regulate emissions of methane in December.

What does this mean for the climate?

In a call with reporters on Thursday, Anne Idsal, assistant administrator of the EPA’s Office of Air and Radiation, said the Obama-era regulations had added “pretty considerable extra costs to domestic energy production while providing just minimal environmental benefit.” She also said that while natural gas production in the U.S. has almost doubled since 1990, methane emissions from the natural gas industry has fallen by near 15%.

“We fully expect those ongoing downward trends in emissions to continue,” she said. The EPA also said it will open a 60-day comment period on the proposal, and schedule a hearing.

However, Mann says the rollback is just a part of “a total full-frontal attack on environmental regulation under the current Administration.” He points to the EPA’s loosening of limits on carbon emissions, and the Administration’s desire to provide subsidies to the coal industry.

Other environmental experts and advocates also worry about the consequences of Thursday’s announcement.

“Today’s actions will create a tremendous amount of additional pollution we didn’t need to have, both from existing wells and new wells,” Siegel tells TIME.

“You cannot curb the climate change problem, you cannot avoid catastrophic warming, if you don’t curb methane along with carbon dioxide and other greenhouse gases,” says NRDC’s Doniger.

“This is an unnecessary leap backwards,” adds Rob Jackson, an environmental scientist at Stanford. “Very few people in the public or the industry want this rollback.”

— with reporting by Justin Worland

Write to Madeleine Carlisle at madeleine.carlisle@time.com.