Colorful reef fish in Papahānaumokuākea Marine National Monument James Watt

Marine Park (n.): any area of the marine environment that has been reserved by federal, state, territorial, tribal, or local laws or regulations to provide lasting protection for part or all of the natural and cultural resources therein.

Chilean president Michelle Bachelet announced last week the creation of one of the world’s largest marine parks around Easter Island, located near a British-administered marine protected area around the Pitcairn Islands. Not to be outdone, President Obama unveiled two new marine sanctuaries in the tidal waters of Maryland and in Lake Michigan.

The language in these announcements can be confusing because there so many ways to describe a patch of protected water. It’s best to start at the top of the pyramid.

In the United States, a marine protected area, or MPA, broadly encompasses just about any watery area that enjoys some level of specific legal safeguard. Sanctuaries, reserves, preserves…they’re all types of marine protected areas. They’re not even exclusively federal. Some MPAs are state or local creations.

Since MPAs come in so many flavors, the designation alone provides very little information. It doesn’t tell you why the area has received the designation, nor does it indicate what you can and can’t do in the water. To dig deeper, you need to understand both the “primary conservation focus” (the government’s reason for protecting the area) and the “level of protection” (the activities allowed or prohibited).

Some examples help illustrate the subtleties. The National Oceanic and Atmospheric Administration established Thunder Bay National Marine Sanctuary in 2000 to protect a remarkable collection of Great Lakes shipwrecks, some more than 150 years old. Since the area’s value is cultural, NOAA allows recreational and commercial fishing on the site. Navassa National Wildlife Refuge, in contrast, was established in 1999 to protect the ecosystem near Haiti’s Tiburon peninsula, so fishing is prohibited and the area is completely closed to the public.

Three other terms also deserve special attention. A marine reserve is one of the most restrictive forms of MPAs, where removing almost anything—fish, rocks, or cultural artifacts—is typically illegal. For this reason, marine reserves are relatively rare. California’s Matlahuayl State Marine Reserve off San Diego, with its undersea canyons and shark-infested kelp forests, is an example of a no-take reserve.

Marine national monuments have similar levels of restriction. They differ from other reserves in that the statutory authority to declare a national monument comes from the Antiquities Act—which usually involves the U.S. Department of the Interior and NOAA, sometimes in conjunction with other agencies. Marine national monuments like Hawaii’s Papahānaumokuākea are nearly off-limits to any kind of resource extraction, with exceptions for traditional uses by indigenous peoples and scientific research.

There are also a small number of marine national parks, which are designated by Congress. Legislators can specify the level of protection established at each of these, so it’s difficult to generalize, but the marine national monuments typically receive greater protection. Dry Tortugas National Park in Florida, for example, has no-fishing areas, but there are other places in the park where fishing is permitted.

Things get even more complicated abroad. Most reporters refer to international sites as “marine parks” or “marine sanctuaries” because they don’t carry specific legal implications. Unfortunately, to understand the levels of protection in non-U.S. areas, you have to go site by site.

Here’s a suggestion: If you’re in any kind of protected area, don’t take a chance. Leave the fish, the plants, and the cultural artifacts alone.

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