A tiny island nation that controls a vast area of the Pacific Ocean has announced it will ban all commercial fishing in a massive marine park that is the size of California.

Anote Tong, the president of Kiribati—a chain of islands about halfway between Hawaii and Fiji—announced Monday that commercial fishing will end in the country's Phoenix Islands Protected Area on January 1, 2015.

"We will also close the area around the southern Line Islands to commercial fishing to allow the area to recover," said Tong, who spoke at the Our Ocean conference hosted by the U.S. State Department in Washington, D.C. The southern Line Islands also will be closed to fishing by the beginning of next year.

The Phoenix Islands and the southern Line Islands represent some of the most pristine coral reef archipelagos in the Pacific, says National Geographic Explorer-in-Residence Enric Sala, who led the first underwater expedition to the five uninhabited southern Line Islands in 2009 as part of National Geographic's Pristine Seas project.

Sala's team of scientists found healthy coral reefs, abundant predator populations, and pristine lagoons carpeted with giant clams and shark nurseries.

"Diving in the southern Line Islands is like getting in a time machine and traveling back to the reefs of the past, when sharks—and not humans—were the top predators," says Sala.

Marine scientist Amanda Keledjian of Oceana, an international nonprofit focused on ocean conservation, calls Kiribati's announcement "very significant." Decreasing the impact of fishing will "preserve biodiversity, large predators, and reefs," says Keledjian.

History of a Marine Park?

In 2006, Kiribati declared the Phoenix Islands Protected Area. The park was expanded in 2008, becoming the largest marine protected area in the world at that time.

About as large as California, the 164,200-square-mile (425,300-square-kilometer) park contains pristine reefs and eight coral atolls teeming with fish and birds. The region is uninhabited, save for about 50 people living on one of the atolls.

However, since the declaration, Kiribati has been criticized by some scientists and environmentalists for failing to protect the area from commercial fishing. In announcing the park Tong had said publicly that it would be "off limits to fishing and other extractive uses."

In practice, however, the nation banned commercial fishing only in the 3 percent of the reserve around the islands. The rest of the zone remained open to industrial tuna fishers, who have steadily increased their activities.

Tong's latest announcement is an "amazing action that shows what is possible with leadership," said Catherine Novelli, the U.S. Under Secretary of State for Economic Growth, Energy, and the Environment, at the Our Ocean conference.

Tong said that the reserve "is an investment in the future and our contribution to humanity in the preservation of marine life."

Still, he cautioned that declarations of marine protected areas "have no meanings unless they are enforced." He said technology will be needed to help monitor the vast area, such as aircraft and satellite-based remote sensing.

Tong, whose country has just 100,000 people, called on other nations to help. "Let us pool our resources to protect this gift, our mother ocean," he said. "Inaction is no longer an option."

The Gem of the Southern Line Islands

Tong's government has specifically declared that the area 12 nautical miles off the southern Line Islands will be protected.

Sala calls it a "great first step" and says he hopes the protection zone may eventually be expanded. It has the potential to be self-sustaining financially with ecotourism, he adds.

(Look for National Geographic magazine's story on the southern Line Islands in the September issue. Also see National Geographic Channel's documentary on the area called Journey to Shark Eden.)

"If you think of the ocean as a bank account in which everybody withdraws but nobody makes a deposit, then protected marine reserves are like savings accounts that produce interest," Sala told the conference.

He explained that after fishing was stopped in a marine reserve along Spain's Mediterranean coast, large fish quickly returned. The fish increased so much in population that they spread outside of the reserve. That revived the fishery and created jobs, in addition to those supported by tourism.

Global Next Steps?

At the Our Ocean conference, U.S. Secretary of State John Kerry asked the heads of state, delegates, nonprofit leaders, scientists, and industry representatives from 80 countries to "develop a plan that protects more marine habitats." Less than 2 percent of the ocean is currently protected, he noted. (Related: "With Millions of Tons of Plastic in Oceans, More Scientists Studying Impact.")

And yet the ocean supports the livelihoods of up to 12 percent of the world's population, Kerry said, adding that about half the world's population depends on seafood for a significant portion of its protein. (Related: "John Kerry Urges Support for Ross Sea Antarctic Ocean Reserve.")

"The ocean is essential for maintaining the environment in which we all live," Kerry said, explaining that it recycles carbon, water, air, and nutrients. It is also home to millions of species.

"The importance of the ocean for life itself cannot be overstated," he said.

He added that President Obama may soon announce additional protected areas in U.S. waters. He asked the other participants in the conference to "walk away with a plan" to protect more of the ocean.

Follow Brian Clark Howard on Twitter and Google+.