As US president-elect and prior to that as a candidate, Donald Trump has taken many positions that dismay environmental advocates. The New York businessman turned politician, who said he believed global warming is a hoax before backtracking on it temporarily last week, has promised to roll back most of achievements of the Obama era in curbing greenhouse gas emissions.

Once sworn in, the newly elected office holder is seen as being in a favorable position to reverse some of President Barack Obama's efforts to reduce carbon emissions, although jobs lost in coal mining over the past decade may be gone forever. Any new energy jobs created are more likely to go to rich states like Texas with its oil and shale exploration industries, observers say.

With a pledge to bring back “tens of thousands” of mining jobs, Trump handily won hundreds of thousands of votes in coal-rich states such as Kentucky and West Virginia in the Nov. 8 election. But while Republicans have blamed overregulation for the decline of coal and some companies in the sector have also blamed Chinese dumping, figures published by the US Department of Energy show that the main reason – alongside plummeting solar and wind energy prices – is the fossil fuels industry’s embrace of fracking to produce cheaper, more abundant shale gas.

The new president nevertheless may be able to fulfil some of his promises to the fossil fuels and petrochemical industries, such as repealing the Clean Power Act, which places emphasis on renewable energy sources. Lawyers for the state of Oklahoma wrote in an opinion piece for the Wall Street Journal that Trump could order the EPA to cease all efforts to enforce and implement the act. The agency would then extend all of the regulation’s deadlines, enter an administrative stay and commence regulatory proceedings to rescind Obama’s executive order.

In one of the wort-case scenarios for environmentalists, Trump could also strike the US signature from the Paris climate agreement signed by President Obama earlier this month. Internal documents from his transition team leaked to the news agency Associated Press (AP) suggest the primary targets will be removing caps on carbon emissions from coal-fired power plants, as well as lifting restrictions placed by the Environmental Protection Agency (EPA) on harmful emissions and chemical-laden waste water from fracking.

Along with the fracking industry, Republicans across the country, especially in resource-rich states, have long been trying to curb the EPA’s power to regulate, thus far with only modest success. Under Trump, they may have better luck. Heading the new administration’s transition team on environmental policy is Myron Ebell, director of the Center for Energy and Environment at the Competitive Enterprise Institute, a libertarian think-tank that AP says receives financial aid from the fossil fuel industry. According to the news agency, Ebell has said he wants to see the Paris climate agreement consigned to the “dustbin of history.”

Legal and environmental experts commenting on the likelihood of the US ratification being reversed, have said they believe the new president would have the power to do so. But even without a formal withdrawal, Trump could simply order the EPA not to take any action toward reducing greenhouse gas emissions by at least 26% below 2005 levels within the next 10 years, s the US has agreed. The new president and the Republican-led Congress could also gut the agency's $8 billion budget. During the campaign, the candidate said doing this could be a way to offset some of the cost of his planned tax cuts.

However, delivering on his promise to take a wrecking ball to the Environmental Protection Agency (EPA) altogether may be one of the hardest challenges Trump could face, some commentators maintain. The environmental watchdog, a presidential cabinet agency, was founded in 1970 during the administration of a Republican, Richard Nixon. Dismantling it would require congressional approval, and the opposition could block it with a filibuster.

Beyond that, environmental groups are already said to be lining up to defend Obama's legacy in court. “We anticipate challenging every single attempt to roll back regulations on air, water and climate,” the Sierra Club’s executive director, Michael Brune, told the AP, adding that fundraising for environmental causes has skyrocketed, since Trump's election.