The exclusive economic zone (EEZ) of the United States, defined by the Magnuson-Stevens Fishery Conservation and Management Act of 1976, extends from the shores of all U.S. land – the coastlines of the lower 48 states, Alaska, Hawaii, Puerto Rico, the U.S. Virgin Islands, and several islands or island groups in the Pacific – out to a distance of 200 nautical miles. It’s the largest EEZ in the world. Estimates vary widely – often because of confusion between statute miles and nautical miles – but the U.S. EEZ is around 4 million square statute miles, or more than 3 million square nautical miles.

The U.S. Coast Guard is responsible for protecting the resources contained within this area, from the fish in the water to the minerals beneath the ocean floor. Its duty to protect American natural resources dates to 1822, when its predecessor, the Revenue Marine, was charged with protecting federal timber in Florida from poachers.

The service’s environmental stewardship role has expanded to include the enforcement of laws protecting the marine environment.

Today the Coast Guard protects the nation’s living marine resources in several ways. Much of its work in this area involves the enforcement of fisheries laws within the U.S. EEZ: protecting the EEZ and other important areas from the encroachment of foreign fishing vessels; enforcing domestic fisheries laws; and developing and enforcing international fisheries agreements, often in joint operations conducted under treaty with foreign counterparts.

According to the Food and Agriculture Organization of the United Nations, more than three-fourths of the world’s marine fish stocks are either fully exploited or depleted faster than they can regenerate. In the U.S. EEZ, which contains one-fifth of the world’s fishery resources, overfishing could bring serious economic consequences. In December 2012, the National Marine Fisheries Service (NMFS) released its most recent annual statistics in “Fisheries Economics of the U.S., 2011: Economics and Sociocultural Status and Trends Series” Memorandum, estimating the overall value of U.S. commercial and recreational fishing in 2011: Together they contributed $199 billion in sales and 1.7 million jobs to the U.S. economy. The Coast Guard, charged with enforcing the eight regional fisheries management plans, conducted about 6,000 fisheries enforcement boardings in 2012.

The service’s environmental stewardship role has expanded to include the enforcement of laws protecting the marine environment. Through its Marine Protected Species program, the Coast Guard works with NMFS and the U.S. Fish and Wildlife Service (FWS) to develop and enforce regulations that help protect the nation’s protected marine species – reinforcing protection zones around humpback whales, educating recreational boaters about the danger they pose to Florida manatees, removing derelict fishing nets from reefs, airlifting orphaned walrus calves to safety, or, in September 2013, partnering with a nature center in Boca Raton, Fla., to release more than 500 protected sea turtle hatchlings directly over a coastal reef off Florida’s Atlantic Coast.

The service’s environmental stewardship role has expanded to include the enforcement of laws protecting the marine environment.

Other potential sources of harm to the marine environment include the introduction of invasive species, unauthorized ocean dumping, and spills of oil and hazardous chemicals. The Coast Guard, through its Marine Environmental Protection program, counters these threats in several ways: educating the public; responding to emergencies and containing hazardous spills; developing and enforcing regulations through inspections, patrols, and boardings; and providing critical support to agencies responding to environmental disasters.