New Zealand’s government announced this week a plan to create a 240,000-square-mile ocean sanctuary in the Kermadec region, off the northeast coast of the country’s North Island.

The move expands the country’s old marine reserves 35 times—and puts the world’s largest system of underwater volcanoes and the world’s second-deepest trench under full protection.

That means no fishing, mining, oil exploration, or any other human disturbances can take place within the France-size reserve.

“It will cover 15 percent of New Zealand’s Exclusive Economic Zone, an area twice the size of our landmass, and 50 times the size of our largest national park,” Prime Minister John Key said in a statement. “As well as being home to a wide range of marine species, the Kermadec region is one of the most geographically and geologically diverse areas in the world.”

The Pew Environment Group, which has been lobbying for the creation of the reserve, said the large reserve would help protect the region’s migratory species, such as whales and sea turtles.

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(Map: Courtesy Department of Conservation New Zealand)

“We are just beginning to understand the abundance of life there, but we know that creating this marine sanctuary will safeguard rare habitats and species critical for healthy ecosystems throughout the South Pacific,” said Bronwen Golder, who leads Pew’s Global Ocean Legacy campaign in New Zealand.

The move marks a positive step toward Pew’s Global Ocean Legacy goal to designate 30 percent of the ocean as marine reserves—a percentage conservationists say is needed for reserves to have a meaningful impact on ocean habitat. Today, only about 3 percent of the world’s oceans are under any sort of protection.

That’s led to massive levels of overfishing, which is blamed for reducing the number of large ocean fish, including the bluefin tuna, to just 10 percent of preindustrial populations. The lack of protections could also allow for future habitat destruction, as new technologies are making underwater mineral mining a potentially profitable industry.

Still, the past decade has seen a sea change in marine reserve designations, starting with the United States declaring the 140,000-square-mile Papahānaumokuākea Marine National Monument northwest of Hawaii in 2006, and Britain’s move to designate 300,000 square miles of South Pacific Ocean as part of the Pitcairn Islands Marine Reserve in 2013.