Donald Trump's policies can be hard to pin down, but it's clear that on environmental issues-especially climate change and energy-a President Trump will do big damage, fast. President Barack Obama's environmental agenda relied heavily on executive actions-actions that Trump can all but erase in his first days, if not first hours, in office, especially with Republicans controlling Capitol Hill.

During the campaign, Trump threatened to "cancel" the Paris Agreement on climate change, which he has called a "hoax." He pledged to eliminate regulations on oil and gas drilling. He called the Environmental Protection Agency's work "a disgrace." He said he would eliminate all "unnecessary" energy industry regulations, and promised "complete" U.S. independence from foreign oil.

Of course, making campaign promises is one thing, and fulfilling them quite another. Trump has already said his "beautiful" U.S.-Mexico border wall could be a fence in some places. And he won't be able to revoke NAFTA or impose high tariffs on goods from China and Mexico without bipartisan support from Congress, something that could prove elusive.

But on environmental issues, Trump has been unequivocal. He will reportedly install prominent global warming skeptic Myron Ebell as head of the EPA. His new transition website says the incoming administration will "scrap" the Clean Power Plan, the centerpiece of Obama's agenda to address climate change.

The Obama administration's moratorium on coal-mining leasing on public lands? Gone.

Regulations enacted earlier this year to reduce heat-trapping methane leakage from oil and gas fracking? Gone.

The "Waters of the United States" rule, finalized by the EPA and U.S. Army Corps of Engineers this summer, which would give new protections to wetlands, rivers, and streams? Gone.

The controversial Keystone XL tar sands pipeline that Obama rejected a year ago? Back on the table.

Scrapping the Clean Power Plan (CPP)-which regulates carbon pollution from power plants and other stationary sources-will be more complicated, but the question of its demise is not if, but when. The plan has been in limbo since February, when the Supreme Court took the unprecedented step of suspending it. But as soon as Trump fills the open Supreme Court seat, the CPP looks headed for the dustbin of history. The very future of the EPA is in doubt, given Trump's selection of Ebell to head his EPA transition team and possibly the agency.

As for the climate agreement reached last December in Paris, Trump can't, as he likes to say, just "cancel" it. (The United States, after all, is just a single participant in the international deal.) Under the rules of the accord, the United States will remain a party to the agreement for at least four years. But Trump could easily simply ignore the deal and refuse to fulfill the voluntary greenhouse gas reductions that the Obama administration committed to. And if a Trump-Pence administration wanted to speed up that four-year timeline, it could try to pull the United States out of the entire United Nations Framework on Climate Change-the international treaty, ratified by the U.S. Senate under George H.W. Bush, that created the Kyoto Protocol and Paris Agreement. Such a move would be nothing less than a "nuclear option" for global climate change diplomacy.

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TO AMERICAN ENVIRONMENTALISTS, this imminent rollback of President Obama's accomplishments feels like a hangover with a punch in the face. "I honestly don't know how to describe it," Jaime Henn, the communications director of the international climate justice group 350.org, told me. "It's like when something truly awful happens-loud noises and bright lights hurt you."

Such feelings of disorientation and anger are, of course, shared by tens of millions of other citizens who are appalled by the coming Trump era. What makes greens' dismay especially intense is their awareness of what's at stake. With global temperatures rising and the planet's oceans becoming more acidic, further delay on slashing greenhouse gas emissions spells planetary disaster. "I imagine that the damage from this election will be measured in geologic time," author-activist Bill McKibben told The Washington Post.

That's not hyperbole. Under the Paris deal, about 20 percent of planetary greenhouse gas reductions were supposed to come from the United States. American inaction, then, will put Earth on track to bust right through a 2 degrees Celsius temperature rise-the level beyond which scientists call a "danger zone."

But if environmentalists feel beaten down, they insist they won't be beat. Greens are determined to fight the Trump-Pence administration and an anti-environmental Congress on all fronts. During a Wednesday briefing at the National Press Club, the leaders of the largest environmental organizations promised that, even as the movement is pressed into rearguard actions, it won't retreat.

"We are going to do everything we can to continue making progress on climate change," said Gene Karpinski, president of the League of Conservation Voters. "We're going to keep in [Trump's] face. … We'll be in the Congress, in the courts, in the boardrooms, in the streets, organizing the broad public that supports action on climate change."

Michael Brune, executive director of the Sierra Club, promised that environmentalists won't "cower." "Today, we aren't defeated-we are determined," he said. "We can guarantee [Trump] the hardest fight of his political life every step of the way."

Environmentalists in other countries are expressing the same spirit of resolve.

As Americans were casting their ballots last Tuesday, government officials and advocates from around the world were gathering in Marrakesh, Morocco, to start implementing the Paris Agreement. News of Trump's surprising victory led to "lots of hugs, lots of red eyes, lots of bewildered faces," as one U.S. environmentalist described the situation to me. But in the days since, the initial shock has morphed into a "determination bubbling up around the conference center."

Fears that U.S. inaction would become contagious have dissipated as many countries have pledged to continue ratcheting down emissions, regardless of the Trump administration's position. Climate activists have been especially buoyed by strong statements from the world's largest emitter, China. "It is global society's will that all want to cooperate to combat climate change," a senior Chinese negotiator said in Marrakesh on Friday. The negotiator added that "any movement by the new U.S. government" won't distract China from its move toward a renewable energy economy.

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While American environmental leaders say they have no interest in sugarcoating the situation-"Make no mistake, the election of Donald Trump could be devastating for our climate," the Sierra Club's Brune said-they also point out that, in some ways, they've seen this movie before. Ronald Reagan's 1980 election, for example, led to a rollback of Jimmy Carter's environmental policies and the ascendance of the anti-environmentalist James Watt to Interior Secretary. In 1994, the Republican takeover of the House and Newt Gingrich's Contract with America threatened to rewrite the Clean Air and Clean Water Acts. After George W. Bush came into office in 2000, he pulled the United States out of the Kyoto Protocol.

But in each case, the environmental movement was able to prevent the worst assaults. Watt lasted only two years at the Interior Department. Gingrich never accomplished his pledge to weaken the Clean Air and Clean Water Acts. And even in the midst of the Bush administration, grassroots opposition succeeded in blocking the proposed construction of more than 180 coal-fired power plants. "They have tried this before, and we all bear the scars of those campaigns," Anna Aurilio, director of Environment America's D.C. office, said at last week's press conference. "No one went to ballot box [in 2016] voting for dirty air or dirty water."

There is, however, one obvious problem with the historical comparisons. In the past, there was always some curb against anti-environment overreach: A Democratic Congress during the Reagan era, Clinton's veto pen during the Gingrich revolution, and a Democratic Senate during the first years of the Bush administration. This time, there is no check and no balance.

To be sure, environmentalists are expert litigators, and they'll use the courts to challenge abuses by oil and gas companies and other polluters. That is, unless-or, as the case may be, until-the Republican-controlled House and Senate seek to change the laws by rewriting bedrock statutes like the Clean Air and Clean Water Acts and the National Environmental Protection Act. There may even be an attempt to divest the country's national parks and national forests, as called for in the official Republican Party platform.

But such efforts could blow up in the GOP's face. While climate change has become, in recent years, a surprising new front in the culture wars (according to the director of the Yale Project on Climate Change Communication, global warming is more polarizing than abortion or gay marriage), an overwhelming majority of Americans support laws that protect air and water quality and endangered species.

Despite what Oklahoma Senator James Inhofe might claim, there's no evidence that Trump has any kind of mandate to repeal environmental protections. In fact, in some states that Trump carried, voters also cast ballots in favor of the environment. In Florida, for example, voters slapped down a ballot initiative that would have kneecapped the state's rooftop solar industry. And in North Carolina, Governor Pat McCrory's defeat was due, in part, to his awful handling of a massive coal ash spill by Duke Energy.

With little to no chance of achieving environmental progress at the federal level, greens are planning to refocus their energies on state and local governments.

"We have to get smart about the states," say 350.org's Henn. "I think you will see a lot more campaigns targeting state governments and businesses."

Environmental groups have a strong foundation on which to build. In September, California Governor Jerry Brown signed a sweeping law requiring the state to cut emissions to 40 percent below 1990 levels by 2030. Nine Northeast and Mid-Atlantic states are part of a regional initiative to reduce emissions, while more than 30 states have renewable energy standards in place that mandate shifts away from fossil fuels. A growing number of cities-including rather unusual suspects like Salt Lake City and San Diego-have committed to powering themselves 100 percent by renewable energy by 2050.

But perhaps environmentalists' greatest source of optimism comes from an unlikely direction-the free market. Among Donald Trump's many bloated campaign boasts, one of the most outlandish was his promise to "put the [coal] miners back to work." It's a claim that's more magical thinking than real-life policy prescription. Cheap natural gas has all but put the coal industry in the grave. At the same time, the prices of wind and solar energy are plummeting. In 2015, wind and solar accounted for two-thirds of newly installed power generation, leading a reporter for Bloomberg to declare that the shift to renewable energy may be "unstoppable."

Indeed. On November 7, venture capitalists were busy directing investments to the innovators working on electric vehicles, advanced energy storage devices, next-generation solar, and other clean energy technologies. On November 9, all of that work was still going on. As the Sierra Club's Brune points out, "Fortune 500 companies-Apple, Google, Ikea, even GM-are investing in clean energy. Trump-Pence-[Paul] Ryan can't touch that." Strange though it may be, ExxonMobil is more enlightened on climate change than Team Trump.

For some greens, this new faith in the market may prove to be just as disorienting as having Donald and Melania living in the White House. Since the era of 19th-century American naturalist John Muir, environmentalism has always looked askance at free-market fundamentalism: Forests and free-running rivers should trump making a buck from timber and electricity, or so the thinking goes. For at least the last 40 years, environmental groups have used the power of the state and the levers of the law to restrain and correct the market's environmental damage. Now those tools are less available. And so, environmentalists find themselves in the odd position of putting their faith in Big Business to save the planet.