OREANDA-NEWS. Donald Trump's victory in the presidential election has thrown into doubt the longevity of climate and environmental regulations President Barack Obama's administration has spent the last eight years developing.

A Trump administration, backed by Republican majorities in both chambers of the US Congress, could target existing rules limiting greenhouse gas emissions from power plants and soften or block rules requiring oil and gas producers to find and repair methane leaks from new oil and gas facilities. The administration could also try to weaken light-duty fuel-economy standards that apply from 2022-25 during a mid-term review that starts next year.

The surprise election win by Trump, who has actively campaigned against federal regulations and is skeptical that greenhouse gas emissions from humans are the leading driver of climate change, also puts into jeopardy a set of final regulations that President Barack Obama aims to release before leaving office on 20 January.

Those final administration rules would limit venting and flaring from oil and gas producers on federal land, heighten environmental standards at coal mines, set biofuel blending requirements for 2017, and determine which offshore areas will be open for oil and gas leasing from 2017-22. Trump could seek to minimize the effect of these last-minute rules or Congress could block them entirely.

Trump's electoral victory stunned many officials in the energy sector who expected Democrat Hillary Clinton to win the presidency based on public polling. Trump during his campaign has sketched out industry-friendly energy policies but has offered few concrete ideas for what he will do, beyond expanding energy development on federal lands and limiting government oversight.

Trump may find it harder than he expected to meet campaign vows to rescind, on his first day of office, existing regulations such as Clean Power Plan. The incoming administration might need to complete a full notice-and-comment rulemaking to remove those and other final regulations. The new administration alternatively could selectively enforce existing rules or, if rules are still under review in court, seek regulatory reconsideration.

"It is a virtual certainty the Clean Power Plan will be revoked. The question now is how," energy lobbyist Jeff Holmstead said today on a call hosted by his law firm Bracewell.

Energy officials expect the Trump administration could revisit existing rules setting fuel economy standards for cars and light-duty trucks, implementation of the renewable fuels standard, federal standards for hydraulic fracturing on public lands, energy efficiency standards for appliances and a new definition of which waters in the US are subject to the Clean Water Act.

Environmental groups hope Trump's victory will embolden Obama to take tough environmental actions in the remainder of his term, such as rerouting the 470,000 b/d Dakota Access pipeline or using his executive authority to put arctic waters and the Atlantic off-limits to future oil and gas development. They are also promising a fight against actions that threaten environmental rules.

"If Donald Trump thinks he can launch a big polluter assault on our air, waters, wildlife and lands, we will build a wall of opposition to stop him," Natural Resources Defense Council president Rhea Suh said.

But even if environmentalists succeed in challenging some actions by the Trump administration, the Republican Congress could weaken landmark environmental statutes such as the Clean Air Act and the National Environmental Policy Act that have formed the basis for recent regulatory actions by Obama. House speaker Paul Ryan (R-Wisconsin) wants to put limits on new regulations and give states more authority over environmental protections and energy production on public lands.

Industry officials say any last-minute actions by Obama could be undone by the incoming administration. If Obama decides to withdraw arctic waters and the Atlantic from oil and gas leasing, for example, they expect Trump could rescind those withdrawals and take actions to open those areas to leasing.