Distribution

The range of Chelonia mydas extends throughout tropical and subtropical oceans worldwide. There are two major subpopulations of C. mydas, the Atlantic and the Eastern Pacific subpopulations. Each population is genetically-distinct, with has its own set of nesting and feeding grounds within the population's known range.
All the five species of marine turtles are threatened.

C. mydas distribution. Red circles are known major nesting sites. Yellow circles represent minor nesting locations.

Atlantic subpopulation
Chelonia mydas can generally be found throughout the entire Atlantic Ocean. Individuals have been spotted as far north as Canada in the Western Atlantic and the British Isles in the east. The subpopulation's southern range is known until past the southern tip of Africa in the east and Argentina in the Western Atlantic. The major nesting sites in the region can be found on various islands in the Caribbean, along the eastern shores of the continental United States, the eastern coast of the South American continent and most notably, on isolated islands in the South Atlantic.
In the Caribbean, major nesting sites have been identified on Aves Island, the U.S. Virgin Islands, Puerto Rico and Costa Rica. One of the most important nesting grounds for the region's green turtle population can be located in Tortuguero in Costa Rica.
In fact, a great majority of the Caribbean region's C. mydas population hails from a few beaches in Tortuguero. Within United States waters, minor nesting sites have been noted in the states of Georgia, North and South Carolina and all along the east coast of Florida. Hutchinson Island in particular is a major nesting area in Florida waters. Notable nesting locations in South America include secluded beaches in Surinam and French Guiana. In the Southern Atlantic Ocean, the most notable nesting grounds for Chelonia mydas are found on the island of Ascension. On that particular island, annual nesting occurs in the volume of around 6,000 to 13,000 individual turtle nests.
In contrast with the sporadic distribution of their nesting sites, Chelonia mydas feeding grounds are much more widely distributed throughout the region. Important feeding grounds for the green sea turtle in Florida include Indian River Lagoon, the Florida Keys, Florida Bay, Homosassa, Crystal River and Cedar Key.

Indo-Pacific subpopulation
In the Pacific, the range of the green turtle reaches as far north as the southern coast of Alaska and as far south as Chile in the east. The turtle's distribution in the Western Pacific is known as far north as Japan and even southern parts of Russia's Pacific coast and as far south as the northern tip of New Zealand and a few islands further south of Tasmania. The turtles can be found throughout the entire range of the Indian Ocean.
Significant nesting grounds are scattered throughout the entire region. Pacific green turtle nesting grounds are found in Mexico, the Hawaiian Islands, the South Pacific, the northern coast of Australia and Southeast Asia. In the Indian Ocean, major nesting colonies have been recorded in India, Pakistan and other coastal countries in the region. A few nesting grounds have been reported along the east coast of the African continent including some islands in the waters around Madagascar.
East Pacific green turtles nesting grounds are well-studied all along the Mexican coast. These turtles have been found to feed in seagrass pastures in the Gulf of California. Green turtles belonging to the distinct Hawaiian subpopulation are known to nest at the protected French Frigate Shoals some 800 kilometers to the west of the Hawaiian Islands. In the Philippines, green turtles are known to nest in the Turtle Islands along with closely-related hawksbill turtles. There are also a few nesting beaches in Indonesia, one of them in the Meru Betiri National Reserve in East Java.] The green sea turtles on the Great Barrier Reef have two genetically distinct populations; one in the Northern Great Barrier Reef, and the other in the Southern half of the reef. Within the reef, twenty separate locations consisting of small islands and cays were identified as nesting sites for either population of C. mydas. Of these, the most important green turtle nesting ground was identified to be on Raine Island.
Farther west into the Indo-Pacific, major nesting sites can be found along the coast of Karachi, Pakistan facing the Arabian Sea. Some specific beaches along the area, such as "Hawksbay" and "Sandspit", are among the most major nesting grounds for the region's C. mydas subpopulation. Sandy beaches along Sindh and Balochistan are also known green turtle nest sites. Some 25 kilometers off the Pakistani coast, Astola island is another known nesting beach.