Pink corals is seen on the Palmyra Atoll, which had an existing 50-mile safeguard. President Obama is expected to create the world’s largest fully protected marine reserve in the central Pacific Ocean. (Jim Maragos/AP)

President Obama will used his legal authority Thursday to create the world’s largest fully protected marine reserve in the central Pacific Ocean, demonstrating his increased willingness to advance a conservation agenda without the need for congressional approval.

By broadening the Pacific Remote Islands National Marine Monument from almost 87,000 square miles to more than 490,000 square miles, Obama has protected more acres of federal land and sea by executive power than any other president in at least 50 years and makes the area off-limits to commercial fishing.

The proclamation — which Secretary of State John F. Kerry announced during an oceans meeting he convened in New York on Thursday — will mean added protections for deep-sea coral reefs and other marine ecosystems that administration officials say are among “the most vulnerable” to the negative effects of climate change. The document signed by Obama noted that the expanded area contains “significant objects of scientific interest that are part of this highly pristine deep sea and open ocean ecosystem with unique biodiversity.”

“We have a responsibility to make sure our kids and their families and the future has the same ocean to serve it in the same way as we have — not to be abused, but to preserve and utilize,” Kerry said at the session, a follow-up to the global ocean conference he held in June. “And we’re talking about an area of ocean that’s nearly twice the size of Texas, and that will be protected in perpetuity from commercial fishing and other resource-extraction activities, like deep-water mining.”

While the new designation is a scaled-back version of an even more ambitious plan the administration had floated in June, it marks the 12th time Obama will have exercised his power under the 1906 Antiquities Act to protect environmental assets. The decision to continue to allow fishing around roughly half the area's islands and atolls aims to limit any economic impact on the U.S. fishing interests.

President Obama wants to use his executive authority to protect more of the Remote Pacific Islands National Marine Monument. Here is footage from already-protected areas in the Palmyra Atoll and Kingman Reef, courtesy of National Geographic. (Editor's note: Music added by PostTV.) (National Geographic)

The unilateral move comes as the administration has found it nearly impossible to achieve many of its other domestic priorities. Consumed by foreign crises and blocked legislatively at home by congressional Republicans, the president and his aides have worked methodically to pursue their environmental objectives through executive action.

Even as it uses its authority to expand a monument first established by George W. Bush in 2009, the White House is preparing to act under the same law to designate national monuments in Chicago’s historic Pullman district and the San Gabriel mountain range northeast of Los Angeles.

“I hope we’re at a tipping point,” said Kristen Brengel, senior director of policy for the National Parks Conservation Association, noting that many of the bills aimed at creating parks and wilderness areas are stalled on Capitol Hill. “It’s every community’s right to go to the president and say, ‘We just can’t get this passed by Congress, can you step in and help us there?’ ”

White House counselor John D. Podesta made it clear during a dinner last week celebrating the 50th anniversary of the Wilderness Act that Obama was eager to designate additional national monuments before leaving office. Obama still trails many of his predecessors when it comes to using the Antiquities Act: Bill Clinton created 23 national monuments, according to the NPCA, while Franklin D. Roosevelt designated 22.

“And believe me, believe me, his signing pen still has some ink left in it,” Podesta said, drawing applause from activists in the audience.

Rep. Rob Bishop, who chairs the House Natural Resources subcommittee on public lands and environmental regulation, said in an interview that the president has stretched the intent of a law designed to protect archeological treasures and “doing it in a roughshod way, with no appreciation for the people who actually know anything” about the sites in question.

“He is using the Antiquities Act not to save or preserve anything, but as a political weapon before the election,” Bishop said, adding that his committee sought to advance wilderness bills but encountered resistance from Democrats who objected to provisions that allowed motorized vehicles in some areas.

Expanding a marine monument?

Under the new designation, the administration will expand the fully protected areas from 50 miles offshore from three remote areas — Johnston Atoll, Wake Atoll and Jarvis Island — to 200 miles, the maximum area within the United States’ exclusive economic zone. The existing, 50-mile safeguards around Kingman Reef and Palmyra Atoll, as well as Howland and Baker islands, which are also part of the existing monuments, will not change.

Obama has protected 297 million acres of federal lands and waters through executive action, surpassing George W. Bush, who safeguarded 211 million acres.

While the islands in question are uninhabited, U.S. tuna operators and some officials in Hawaii and American Samoa have opposed the expansion on the grounds that it could make it more difficult to catch tuna and other species at certain times of year. Fish caught in the area around all seven atolls and islands account for up to 4 percent of the annual U.S. tuna catch in the western and central Pacific, according to the Pew Charitable Trusts.

Sean Martin, president of the Hawaii Longline Association who organized a bus to bring in about 100 fishermen to a public meeting on the proposal in Hono­lulu last month, said the operators of 145 boats that fish in the region want “the opportunity to go where the fish are, hopefully.”

And Claire Poumele, director of the American Samoa Port Authority, said she was concerned about the $600 million worth of fish her territory processes each year: “It definitely could have an impact,” Poumele said.

But scientists and conservationists who have lobbied for the bigger monument argue that these vessels can catch tuna outside the protected zone and that it provides shelter not only for 130 underwater mountains that serve as hot spots for biodiversity but for nearly two dozen species of marine mammals, five types of threatened sea turtles, and a variety of sharks and other predatory fish species.

Referring to the three adjacent areas that will now have more restricted activities, the presidential proclamation states, “These adjacent areas hold a large number of undersea mountains (‘seamounts’) that may provide habitat for colonies of deepwater corals many thousands of years old,” adding that their “pelagic environment provides habitat and forage for tunas, turtles, manta rays, sharks, cetaceans and seabirds that have evolved with a foraging technique that depends on large marine predators.”

“If you put aside the emotion and put aside the rhetoric on both sides, less than 3 percent of the Pacific is in under effective protection,” University of Hawaii professor Robert H. Richmond said.

Marine Conservation Institute chief scientist Elliott Norse, who has been conducting underwater research since 1969, said “the seas have been emptied,” adding the point of the Antiquities Act is “about having places in our realm where we don’t kill off the wildlife.”

Matt Rand, who leads the Pew Charitable Trust’s Global Ocean Legacy project, said that because more than half-a-dozen other nations are considering creating new protected areas in the Pacific, “This could be the wave that ultimately propels these marine reserves to become reality.” Taken together with the U.S. announcement, these areas could encompass more than 2.3 million square miles of sea.