President Obama announced last week that he plans to add massive amounts of territory to the Remote Pacific Islands National Marine Monument, a tract of ocean surrounding seven hard-to-reach islands and atolls in the south-central Pacific Ocean. Obama’s decision will expand the original reserve, created by George W. Bush in the last days of his presidency, by almost five times its original size. The expanded national monument will quintuple the number of seamounts, or underwater mountains, under federal protection, and close almost 780,000 square miles of ocean to tuna fishing.

Obama’s decision has been hailed for its conservation impact by scientists and even by the New York Times editorial board. Gareth Williams, a researcher at Scripps who studies the coral reefs within the reserve, hailed the expanded national monument as protecting some of the most intact natural areas left on the planet. “It’s almost impossible to find another example of that, forests included,” Williams told The Daily Beast. “There are always examples of degradation, but there are very few examples of ecosystems left that are that pristine.”

But plenty of people aren’t happy with Obama’s decision, and the next few months—in which the exact details of the expansion will be up for review—may be contentious ones. These are the groups that have most at stake in opposing the expanded Remote Pacific Islands reserve:

1. Republican lawmakers

Obama’s use of an executive order to establish the reserve expansion angered Republicans in government, who viewed it as an attempt to test the limits of White House authority. Congressman Doc Hastings (R-Wash.), the chairman of the House Natural Resources Committee, was quick to denounce Obama as an “Imperial President” who is “intent on taking unilateral action, behind closed doors, to impose new regulations and layers of restrictive red-tape.”

By Hastings’ standards, then, another candidate for an “imperial presidency” would be George W. Bush, who created four marine national monuments during his time in office, totaling some 300,000 square miles of protected ocean.

2. The commercial fishing industry.

Currently, about 3 percent of the U.S.’ tuna catch in the western and southern Pacific comes from the area now under protection, according to Pew Charitable Trusts. Congressman Hastings has criticized Obama for closing this area to tuna fishing, cautioning that this move will “make the U.S. tuna fleet even less viable, meaning that in the not-too-distant future all of America’s tuna will be caught by foreign vessels.”

Paul Dalzell, a senior scientist with the Western and Central Pacific Regional Fisheries Management Council, echoed this industry-centric approach. “The islands [in the reserve] already have 50-nautical-mile boundaries around them to protect all the coral reef and shallow water habitats, so they’re more than adequately protected already,” Dalzell told The Daily Beast. But for migratory species like tuna, he argues, large-scale ocean reserves have little conservation value, since tuna simply swim beyond the boundaries of the closed areas to be caught by other fleets. The reserve “has no major conservation benefits, will penalize U.S. fishermen, and there’s no net gain,” Dalzell continued.

It’s worth noting that Pew Charitable Trusts, which works on ocean conservation issues, has condemned the Western and Central Pacific Regional Fisheries Management Council for its poor fisheries practices, which it claims are hastening overfishing in the Pacific region.

3. Recreational fishers.

After Bush first established the Remote Pacific Islands reserve in 2009, the American Sportfishing Association successfully petitioned for a recreational fishing exemption within the reserve. Now the group, which represents manufacturers of fishing tackle rather than sport fishermen themselves, plans to push for the exemption to apply throughout the expanded area.

“We believe in almost all instances you can still have marine conservation and make sure that your fisheries resources are in good, healthy condition, and still allow some recreational fishing to take place,” Mike Leonard, a spokesperson for the ASA, told The Daily Beast. The group’s insistence on a recreational fishing exemption is mostly academic, since the areas within the expanded reserve are so remote as to be unreachable to sport fishermen. Williams, who has traveled to the reserve repeatedly for his research, said that he has never seen a recreational fishing boat there.

But Leonard claims that the reserve could set a precedent for the federal government closing more high-use areas to sport fishing. “It seems to be a growing trend that, when you add it up nationally, can be one of those death-by-a-thousand-cuts issues, where you continue to close off areas one by one,” he told the Beast. “Cumulatively that can have a major impact, from a national standpoint, for the entirety of the recreational fishing and boating industry.” Of course, marine reserves won’t keep fishermen from enjoying protected natural spaces—just from using the expensive fishing tackle that the ASA’s members sell.