The election of Donald Trump as president of the United States last Tuesday fell like a lightning bolt on the American environmental community. But it has left many environmentalists energized for battle—albeit against an adversary whose positions are in part still ill-defined.

“The next few years will bring some big fights and also some unpredictable fluidity,” Environmental Defense Fund president Fred Krupp wrote on his organization’s website. “We will ferociously defend America’s bedrock environmental protections.“

“If President-Elect Trump and his allies think the results of this election give them a mandate to roll back this progress they are sorely mistaken,” says League of Conservation Voters president Gene Karpinski in a statement. “To the contrary, polls demonstrate bipartisan support for action on climate change and protections for clean air and clean water, and we urge Donald Trump to respect that support.”

The most consequential battleground is likely to be over the new administration’s climate policy. During the campaign Trump promised to “cancel” the Paris Agreement on climate change and to revoke the Obama Administration’s regulations designed to reduce carbon emissions from power plants—the centerpiece of the U.S. effort to meet its commitment under the Paris Agreement. (Read more about Trump’s stance on climate change.)

But climate is not the only issue on which Trump may depart from the Obama Administration’s environmental policy. Here are three others.

Which Public Lands Should Be Preserved As National Monuments?

More than any president before him, President Barack Obama has used his executive authority under the U.S. Antiquities Act to protect federal lands as national monuments. In his time in office, Obama has designated 23 national monuments across the country. His selections have preserved landscapes and seascapes of ecological significance, as well as cultural touchstones such as New York City’s Stonewall Inn—a gay rights landmark—and the home and final resting place of Latino activist César Chávez.

It is unclear that the incoming Trump Administration would have the legal authority or appetite to revoke any of President Obama’s national monuments, absent an act of Congress.

“It would be unprecedented for President Trump to attempt to revoke a national monument designation—and any attempt to do so would likely be invalidated by the courts,” writes John Ruple, an associate research professor at the University of Utah’s S.J. Quinney School of Law and expert on public land management, in an emailed statement.

“The Antiquities Act gives the president the power to designate national monuments, but not the power to revoke prior monument designations, and two prior U.S. Attorneys General have opined that absent express delegation, the president would be without the power of revocation,” he adds. “If President Trump attempts to revoke a national monument designation, that effort will almost certainly be embroiled in litigation, and the revocation would likely fail.”

Presidents can modify existing national monuments, however. Obama used this power to more than quadruple the size of the Papahānaumokuākea Marine National Monument, established by President George W. Bush in the biologically vibrant waters around Hawaii’s uninhabited northwestern islands. The expanded monument is now 582,578 square miles—larger than all U.S. national parks combined. (Read more about the historic marine preserve.)

Could President Trump downsize that monument or another? Ruple says that there is no precedent for that either. He also notes that Congress has moved only rarely to revoke the status of a national monument. Notable examples include the Shoshone Cavern near Cody, Wyoming, and Castle Pinckney, a small fort off the coast of Charleston, South Carolina.

In these instances, the National Park Service did not have the funding or incentive to maintain the sites, leading Congress to transfer their management back to state and local authorities. This does not appear to be the case for any of President Obama’s national monuments.

But opposition to Obama’s use of the Antiquities Act has been vocal in some Republican circles, notably from Rob Bishop, a Utah congressman who chairs the House of Representatives’ Committee on Natural Resources.

“Right now the executive branch abuses the Antiquities Act to sidestep local voices and the established public process,” writes Parish Braden, the communications director for the Committee on Natural Resources. “Chairman Bishop will continue efforts to bring transparency and local input to all federal land designations including national monument designations.”

Which Waters Should Be Protected From Pollution?

The Clean Water Act of 1977 is a lynchpin in U.S. environmental policy and the country’s main law governing water pollution. The law applies to “navigable waters,” which it defines, unhelpfully, as “waters of the United States.” The argument about what that means has stretched over nearly four decades and three Supreme Court decisions.

The Trump campaign’s official transition website, greatagain.gov, makes clear that the incoming administration will attempt to roll back the Obama Administration’s effort to clarify the matter.

In 2006 the Supreme Court ruled in Rapanos v. United States that the Clean Water Act also applies to waters that have a “significant nexus” with navigable rivers or seas. The “Waters of the United States” rule issued last year by the EPA interprets that as extending the federal government’s jurisdiction to streams, including seasonal ones, that flow into navigable rivers, and also to wetlands located near such streams or rivers.

The EPA argued that the move was scientifically justified, as the quality of navigable waters downstream depends heavily on water quality upstream—polluted water, like clean water, flows downhill.

“From an ecological and scientific perspective, it makes perfect sense,” says Siobhan Fennessy, a Kenyon College biologist who helped review the EPA’s scientific justification for the rule. “It’s very hard to say that the upper reaches of watersheds or wetlands adjacent to rivers don’t have an effect on the water quality downstream.”

“We found that there was overwhelming scientific support that streams and floodplain wetlands are physically, chemically, and biologically connected to downstream navigable waters,” adds Amanda Rodewald, the director of conservation science at the Cornell Lab of Ornithology. Rodewald led the 27-scientist advisory panel that evaluated the EPA’s justification for the rule.

One of the main problems the rule is designed to address is the runoff of nutrients such as nitrogen and phosphorus from fertilized farm fields. High nutrient levels in downstream waters can impact drinking water, and they can also lead to spikes in algae growth that produce low-oxygen “dead zones”—such as the enormous one that has become an annual occurrence at the mouth of the Mississippi. (Find out more about “dead zones.”)

Some landowner and agricultural groups have lambasted the EPA rule as an overreaching infringement of private property rights and an onerous burden on farmers and ranchers.

“It creates confusion and risk by providing the agencies with almost unlimited authority to regulate, at their discretion, any low spot where rainwater collects, including common farm ditches, ephemeral drainages, agricultural ponds, and isolated wetlands found in and near farms and ranches across the nation,” said the American Farm Bureau in a 2015 statement. (In a factsheet, the EPA says that the rule does not change agricultural exemptions, nor does it regulate farm ponds, puddles, groundwater, erosional features, or most ditches.)

Iain Murray of the Competitive Enterprise Institute, a D.C.-based free-market think-tank, wrote in National Review in 2015 that the rule was “an unprecedented power grab” that “twists the plain language of the Clean Water Act.” The Competitive Enterprise Institute’s view of the rule stands to reveal the Trump Administration’s stance: Myron Ebell, a noted climate skeptic and director of the think-tank’s Center for Energy and Environment, has been tapped to lead the Trump campaign’s EPA transition team. (Read more about Ebell and Trump’s denial of climate change.)

Rescinding the EPA rule, which is currently stayed nationwide amid legal action against it, would be a long, legally thorny process, warns the University of Utah’s John Ruple.

“If the administration wants to change any rule that has already been finalized, they’re going to have an uphill battle. It’s not a quick and easy change,” Ruple says. “They’re going to have to solicit public comment. They’re going to have to explain why they want to change the rule—and how science supports their decision. That seems somewhat unlikely.”

Which Public Lands Should Be Open to Fossil Fuel Development?

The Trump transition team has called for renewed fossil fuel development and leasing on public lands and waters, signaling reversals from several policies of the Obama Administration.

“Rather than continuing the current path to undermine and block America’s fossil fuel producers, the Trump Administration will encourage the production of these resources by opening onshore and offshore leasing on federal lands and waters,” the transition’s official website says.

In early 2016, the Obama Administration issued a moratorium on new coal-mining leases on federal land, citing the need to reexamine the decades-old program’s health and environmental impacts. Existing leases produce enough coal to supply U.S. energy needs for 20 years. Trump’s campaign has indicated that he will rescind the moratorium.

U.S. coal production fell by more than 10 percent in 2015 and is down nearly a quarter from its peak in 2008, according to the U.S. Energy Information Administration. The main reason, says the EIA, is not a shortage of coal leases but competition from cheap natural gas.

The explosion of hydraulic fracturing, also known as “fracking,” has made the U.S. the largest producer of natural gas and petroleum in the world. It has contributed to a world oil glut that has oil prices hovering above $40 a barrel, down by more than two-thirds from their 2008 peak.

Fracking has helped the U.S. produce more of its own energy—the country currently produces enough crude oil to meet about 75 percent of its needs—and has also contributed to a drop in carbon emissions. Natural gas emits about 50 to 60 percent of coal’s carbon emissions when burned.

Against this backdrop of a U.S. energy boom, Trump has pledged to cut back federal regulations that affect fracking (which is primarily regulated at the state level). He has promised “complete energy independence,” and to achieve that he wants to open more federal lands and waters to drilling.

A likely target is Alaska. In February 2015, the Obama Administration effectively banned oil exploration on some 22 million acres of federal land and waters in Alaska: 12 million acres on land in the Arctic National Wildlife Refuge (ANWR) and 10 million acres offshore in the Beaufort and Chukchi Seas.

The ruling had little influence on the status quo; most of the protected areas have been off-limits for decades. And to compensate, the Obama Administration opened up tens of millions of acres off the mid-Atlantic coast and in the Gulf of Mexico to drillers. (Find out more about the Obama Administration’s policy on Alaskan oil exploration.)

But the move infuriated Alaska’s congressional representation. More than 90 percent of Alaska’s revenue comes from taxes on oil and gas infrastructure and the oil flowing through the Trans-Alaska Pipeline—which is now a third of what it was at its peak.

To that end, Alaska’s congressional representation will try once again to open up oil exploration in part of the Arctic National Wildlife Refuge (ANWR)—the latest volley in a long-running controversy over drilling for oil in a portion of the 19-million-acre refuge. (Read more about the Arctic National Wildlife Refuge—and the debate over drilling within it.)

“I think you can anticipate members pushing ANWR development early in the next Congress, especially members of the Alaska delegation,” says Braden, the spokesperson for the House Committee on Natural Resources.