On Thursday, President Obama created the world's largest ocean reserve.

The new reserve, an enlargement of the existing Pacific Remote Islands Marine National Monument, nearly quadruples the total amount of US ocean territory that's protected from commercial fishing, oil drilling, and other activities.

it's the world's largest area protected from commercial fishing

Previously, the monument — a cluster of reserves surrounding seven uninhabited islands south and west of Hawaii — covered about 86,888 square miles. The new monument will cover nearly 490,000 square miles in total, with the gains coming from extending the borders to 200 miles off the coasts of Wake Island, Jarvis Island, and Johnston Atoll. This is as far as the US government is permitted to protect, according to international law.

Despite the huge gains, though, the new monument is considerably smaller than the one Obama originally proposed in July, which would have been 782,000 square miles, and extended the protected zone around four other islands as well. Opposition from the commercial tuna fishing industry during the public comment period led to the shrinkage.

At the moment, there's no drilling and not that much fishing in the newly protected area — so the reserve won't be hugely impactful at the start. Still, it's a big step forward in proactively protecting marine habitats on a massive scale.

How the new reserve will work

In 2009, President Bush designated the original Pacific Remote Islands Marine National Monument, along with two other protected areas in the Pacific. The protected monument was made up of the ocean surrounding seven different remote Pacific islands and atolls under US control, and extended about 50 miles out from their shores.

In creating it, Bush relied on executive authority: he used the 1906 Antiquities Act, which allows the president to protect government lands of historic or scientific interest. Obama is using the same act to extend the protected waters for 200 miles off the coasts of three of the seven islands. This 200-mile distance is as far as the US has jurisdiction over, in terms of marine resources.

commercial fishing, resource extraction, and waste dumping are illegal within the area

Inside the national monument area, all commercial fishing, resource extraction, and waste dumping are illegal. Bush made an exception for sport fishing when he designated the original monument, and it will apply to the new area too.

There isn't currently any oil drilling or mining in this area, so the main effect of the expansion will be a cut down on fishing. Tuna fishing, in particular, will be impacted: the Washington Post reports that up to 4 percent of the yearly US tuna catch in the western and central Pacific comes from the area that would have gone under protection under the proposed, larger expansion. This led so protest from fishing and canning groups, such as the Hawaii Longline Association, during the public comment period.

The White House is billing the actual expansion, a bit more than half the size, as a compromise between economic and ecological priorities.

The benefits of protecting the ocean

Marine monuments are the ocean equivalent of national parks — areas of relative wilderness heavily protected from human use.

The area covered by the new reserve features a large number of fish, marine mammal, coral, bird, and plant species that aren't found anywhere else in the world. There are several endangered species, such as the hawksbill sea turtle and the humphead wrasse. Additionally, the expansion increases the total number of protected underwater mountains called seamounts (known to be areas of high biodiversity) to 130, up from 50 in the old reserve.

the reserve is a proactive step in protecting the fish species we eat

While the reserve covers remote areas that don't suffer heavily from local pollution or commercial fishing, there are some tuna fleets that operate in the area. They typically use purse seining techniques, which involve tightening a net around a school of fish attracted to something called a fish aggregating device. In many cases, this technique produces high amounts of bycatch — fish from other, unintended species that are discarded — so tuna fishing can deplete all sorts of fish species in an ecosystem.

Additionally, the reserve is a proactive step in protecting the fish species we do want to eat. Scientists have stressed the importance of expanding protected marine areas, both to preserve endangered species and give fish stocks a chance to recover.

Research has shown that reserves help revive fish stocks in nearby, non-protected areas. It's also shown that large reserves — like the one proposed on Tuesday — are especially effective, because species can move about them freely.

Previously, only about three percent of U.S. territorial waters were protected from commercial fishing, and 95 percent of that area was within the nearby Papahānaumokuākea National Monument, established by President Bush in 2006.

The new reserve dwarfs previous US reserves, nearly quadrupling the amount of US ocean that's protected. It comes as part of a recent global trend of protecting more and more ocean, with the island nation of Kiribati most recently banning fishing throughout their 164,200 square mile reserve.

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