By the close of a two-day conference in Washington on the world's oceans, five nations had pledged to extend marine protections to cover more than a million square miles.

The United States, Palau, the Cook Islands, and the Bahamas unveiled their plans on Tuesday, following Kiribati's announcement Monday that commercial fishing would end in the vast marine reserves in its Pacific Ocean territory by the end of the year.

"We need to do more, but that is a great start," U.S. Secretary of State John Kerry told the heads of state, nonprofit leaders, scientists, and industry representatives from 80 countries at the Our Ocean conference.

Earlier Tuesday, U.S. President Barack Obama proposed an expansion of the Pacific Remote Islands Marine National Monument in the central Pacific, from almost 87,000 square miles (225,000 square kilometers) to nearly 782,000 square miles (2 million square kilometers). (See: "Obama Announces Plan to Create World's Largest Ocean Reserve.")

The new Palau National Marine Sanctuary in the Pacific Ocean will protect 193,000 square miles (500,000 square kilometers), representing 80 percent of the country's exclusive economic zone, or the territorial waters that a nation controls.

"That's about the size of the great state of Texas," said the nation's president, Tommy Remengesau, Jr., who added that the new sanctuary would exclude all industrial-scale fishing and exports of catches.

The Cook Islands in the South Pacific announced an expansion of its ban on commercial fishing from 12 miles (19 kilometers) around each of the 15 islands to 50 miles (80 kilometers) around each island.

The island nation, which shares some government resources with New Zealand, had declared in 2012 that 424,000 square miles (1.1 million square kilometers)—a little more than half of its exclusive economic zone—would become a marine park.

But public pressure in the country resulted in the expansion of the park from the southern islands of the chain to include the northern islands as well, Elizabeth Wright-Koteka, the prime minister's chief of staff, told National Geographic.

"People in the north islands saw the benefits of the reserve, and they said, 'We want that too,'" Wright-Koteka said.

The Bahamas' minister of the environment and housing, Kenred Dorsett, said his country has committed to protecting 20 percent of its ocean territory by 2020, up from 3 percent today. The country designated 15 new marine protected areas earlier this year.

"Ninety-four percent of my country is comprised of the ocean," said Dorsett about the Bahamas, a chain of 700 islands in the Caribbean. "We are truly an ocean state."

Greens Respond

National Geographic Explorer-in-Residence Sylvia Earle called the new reserves "big steps in the right direction." But, she said, "we need to do more."

Earle highlighted Palau's announced reserve as "based on sound science." She said the plan is smart to "allow a small amount of fishing in small areas and then protect the big areas."

Still, it remains to be seen how well the proposed reserves protect fish and the overall marine environment, she said. Many challenges remain, including enforcement and balancing fishing rights.

Marine scientist Amanda Keledjian of Oceana, an international nonprofit focused on ocean conservation, said the new marine reserves are "very significant" acts that "preserve biodiversity, large predators, and reefs."

Building on Science and Tradition

About his island nation's new reserve, Palau's Remengesau said, "We are not anti-fishing, we are pro-fishing sustainably."

Remengesau said he had been a fisherman, but has seen his country's stocks devastated by the international fishing industry.

Restrictions on its activities will allow those stocks to recover. And some of the fish in the protected areas, once their populations rebound, will "spill over" to areas that will still allow fishing.

The action is not without precedent, he noted. "Our ancestors called for a moratorium to ban fishing in certain segments if they saw fish stocks were decreasing."

In 2001, Palau was the first country to create a shark sanctuary. "It is working," Remengesau said. "Studies have shown that a live shark is worth much, much more than a dead shark, and the same goes for all species."

Wright-Koteka added that the Cook Islands government is looking at updating legislation that governs the country's huge marine park, with an eye toward streamlining administration and improving comprehensive management of the fish, water, and seafloor.

"We are under no illusions that this will be a straightforward journey, but we know if we can pull this off we will have created a groundbreaking plan that will safeguard the ocean," she said. "This will hopefully encourage other nations to follow."

Learn more about the Our Ocean conference: