In what is likely Barack Obama’s final environmental action before Donald Trump moves into the White House, the president has just expanded the existing California Coastal National Monument -- adding a mix of lighthouses, rocky outcroppings, stands of redwoods and significant Native American grounds that will be knitted into the existing federal preserve on and off the coast from Humboldt County to Orange County.

The move was applauded by environmentalists who feel a greater urgency to shore up conservation gains before the Obama administration is ushered out. Given the general anti-environmental tenor in Congress, and the Trump administration’s uncertain and unexpressed view on conservation issues, some groups saw the announcement as important not so much because it afforded the California sites protection from encroaching development, but because those areas would be spared from a questionable future.

Generally, monument designations or other categories of protection aim to shield special places from more imminent threats such as energy exploration, logging or other commercial development. In the case of the California additions, there were few such threats. The fear here was of the unknown -- that the desirable coastal land could have eventually been yanked away from federal managers and placed in the hands of those willing to sacrifice its environmental and cultural value.

"The great thing is that this ensures that these areas remain part of the public lands system," said Dan Smuts, senior director of the Pacific region for the Wilderness Society. "It precludes the government disposing of these lands. Given that they are small, scattered parcels along the coast, they are supremely valuable, and it's important that they be kept in the public estate."

Western conservatives have been increasingly pressing the federal government to surrender lands it now owns, and the Republican-controlled Congress has taken up the campaign. On the first day back in session earlier this month, the House made it easier to transfer federal land to states or local entities by overturning a rule requiring a calculation of the value of federal land before such a transfer.

A host of legislators in the intermountain West, led by Utah Gov. Gary Herbert, have long been clamoring for U.S. land management agencies to cede control of federal land to states, which bridle at being managed from Washington. The federal government is the West’s biggest landlord, and the idea of wresting control of vast tracts of deserts and forests is an enduring and uniquely Western motif.

As a candidate, Trump spent scant time discussing public lands issues, which would understandably be unfamiliar to a lifelong New Yorker. Trump’s home state contains less than 1 percent federal land. By comparison, nearly 48 percent of the land in California is held by the federal government.

Even as Trump's personal conservation views are something of a cipher, activists worry that partisanship in Washington could drown out support for even the most laudable projects. Land conservation has historically been somewhat sheltered from the partisan ideology that surrounds other environmental issues, but an anti-government groundswell has made compromise on federal land protections more difficult.

"There is an ideological opposition to the federal government owning and managing even an acre of land," Smuts said. "We are clear-eyed that it will be difficult to make conservation gains in this administration and this Congress. But in my time I have seen the pendulum swing from pro-conservation administrations and back. We have been successful in getting important areas protected under Democrats and Republicans."

Groups lined up Thursday to praise Obama, and to cast a wary glance at the future.

"Our coast belongs to all Californians and preserving its scenic beauty and biodiversity is crucial for California's climate and economic future," said California League of Conservation Voters CEO Sarah Rose in a statement. "With the new presidential administration about to take office, it is crucial we act to make certain our magnificent landscapes and wildlife continue to belong to all of us now, and for generations to come."

Obama's proclamation not only adds 6,200 acres to the existing monument, it significantly amplifies the protections afforded the new sites, which will be managed by the federal Bureau of Land Management.

Obama made the addition by using the Antiquities Act, which allows the president to set aside tracts of federal land or significant places for protection, without the consent of Congress. That 1906 law -- which gives the executive authority to bypass Congress -- has in recent years enraged some Republicans, who see it as a cudgel and frequently characterize its use as "federal land grabs."

Unlike executive orders, which can be undone with the stroke of a presidential pen, monument designations cannot be rescinded by a successor. While some in Washington believe Congress has the right to claw back the decisions, there has not yet been a legal challenge to a presidential monument proclamation.

That could change under a Trump administration. Among the bills taking aim at the Antiquities Act is one proffered this month by Sen. Lisa Murkowski, a Republican from Alaska. The proposal, the Improved National Monument Designation Process Act, would require future national monuments receive approval not only from Congress before designation, but also from the legislature in the state or states affected.

Among the other monument designations made Thursday were three historically significant civil rights sites in Alabama and South Carolina, as well as an expansion of the Cascade-Siskiyou National Monument in Oregon.

Conservation groups in California had long campaigned for adding the sites to the monument, which was first established in 2000 and expanded by Obama in 2014. That cause was championed by Democratic Sen. Barbara Boxer, whose bill to expand the monument stalled before her retirement this year.

The coastal monument is a unique preserve, encompassing rocks and small islands critical for marine species, and historic and cultural sites on beaches and headlands.

The sites added are:

• Trinidad Head (Humboldt County) -- a 60-acre headland reaching into Trinidad Harbor, with a historic lighthouse.

• The Lost Coast Headlands (Humboldt County) -- a former Navy installation on coastal bluffs that provide plant and wildlife habitat.

• Waluplh-Lighthouse Ranch (Humboldt County) -- site of a former 19^th century lighthouse with views of the Eel River Delta, the Pacific and parts of Humboldt Bay.

• Cotoni-Coast Dairies (Santa Cruz County) -- a former dairy and industrial site that is now habitat for rare animals. The waters are home to whales and other marine mammals.

• Piedras Blancas (San Luis Obispo County) -- a historic lighthouse and an area with cultural significance to the Chumash and Salinan tribes.

• Rocks and islands (Orange County) -- formations that provide roosting habitat for sea birds and “haul-out” or resting areas for seals and sea lions.

The first land-based expansion of the California Coastal National Monument came in 2014, when Obama included what came to be called Point Arena-Stornetta Public Lands, about 1,665 acres north of the town of Point Arena in Mendocino County.

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