First sighted by Europeans in 1606, claimed by the United Kingdom in 1868, and part of the Republic of Kiribati since the island nation's independence in 1979, Caroline Island has remained relatively untouched and is considered one of the world's most pristine tropical islands, despite guano mining, copra harvesting, and human habitation in the 19th and 20th centuries. It is home to one of the world's largest populations of the coconut crab and is an important breeding site for seabirds, most notably the sooty tern.
The atoll is best known for its role in celebrations surrounding the arrival of the year 2000 — a 1995 realignment of the International Date Line made Caroline Island one of the first points of land on Earth (outside Antarctica) to see sunrise on January 1, 2000.
Caroline Atoll lies near the southeastern end of the Line Islands, a string of atolls extending across the equator some 1500 km (900 miles) south of the Hawaiian Islands in the central Pacific. The slightly crescent-shaped atoll (3.76 km² or 1.45 mi² in land area) consists of 39 separate islets surrounding a narrow lagoon. Extending approximately 9 km (6 mi) from north to south and 2 km (1 mi) from east to west, the islets rise to a height of only 6 meters (20 ft) above sea level. The islets, like those of all atolls, share a common geologic origin and consist of sand deposits and limestone rock set atop a coral reef.
Three large islets make up the bulk of Caroline's land area: Nake Islet (1.04 km² or 0.40 mi²) at the north; Long Islet (0.76 km² or 0.29 mi²) at the northeast of the lagoon and South Islet (1.07 km² or 0.41 mi²). The remaining assembly of small islets, most of which were named during the 1988 ecological survey, conducted by Angela and Cameron Kepler, fall into four major groupings: the South Nake Islets, the Central Leeward Islets, the Southern Leeward Islets, and the Windward Islets (see map). Caroline's islets are particularly ephemeral — over the course of a century of observation, several of the smallest islets have been documented to appear or disappear entirely following major storms, while the shapes of larger ones have significantly changed.
The central lagoon, roughly 6 km by 0.5 km (3.5 miles by 0.3 miles), is shallow – at most 5–7 m (15–25 ft) in depth – and is crossed repeatedly by narrow coral heads and patch reefs. Reef flats generally extend about 500 m (1600 ft) from shore — although some sources report them to extend more than a kilometer from land — and make boat landings perilous except at high tide. There are no natural landings, anchorages, or deep water openings into the central lagoon; water which spills into the lagoon over shallow channels at high tide is contained within the surrounding reef and remains stable despite ocean tides. Most landings are generally made at a small break in the reef at the northwest corner of South Islet (visible on the satellite photo above).
There is no standing fresh water on Caroline Island, although the Nake and South Islets harbor underground freshwater aquifers (or Ghyben-Herzberg lenses), and wells have been built to tap drinking water for temporary settlements. Soils on Caroline are similarly poor, dominated by coral gravel and sand, with significant organic content present only within stable, forested island centers. Guano deposits make island soil, where it does exist, nitrogen-rich; but even in the oldest and most vegetated regions of the atoll, soils are only a few centimeters (one or two inches) thick.
Like the rest of Kiribati, Caroline Island enjoys a tropical maritime climate – consistently hot and humid. Meteorological records are sparse, but temperatures generally range between 28 and 32 degrees Celsius (82 and 90 degrees Fahrenheit) year-round. Caroline lies within a region of highly variable precipitation, but is estimated to receive an average of 1500 mm (60 in) of rain annually. Tides are on the order of 0.5 m (1.5 ft) and trade winds, generally from the northeast, mean that corner of the island experiences the roughest seas.
Caroline Island is among the most remote islands on earth–230 km (140 mi) from the closest land at Flint Island, 1500 km (930 mi) from the nearest permanent settlement on Kiritimati, 4200 km (2600 mi) from the Kiribati capital of Tarawa, and 5100 km (3200 mi) from the nearest continental land in North America.
Despite more than three centuries of occasional human impact on Caroline, it is considered to be one of very few remaining "near-pristine tropical islands." and has been rated as one of the most unspoiled Pacific atolls. Its relatively undisturbed state has led to Caroline being considered for designation as a World Heritage Site and as a Biosphere Reserve. Ecological surveys documenting the island's flora and fauna have been made intermittently through the later 20th century: Caroline was visited in 1965 by the Pacific Ocean Biological Survey Program, in 1974 by the Line Island Expedition, and in 1988 and 1991 by the United Nations Environment Programme Wildlife Conservation Unit.
Caroline Island is heavily vegetated, and most islets possess three ringed zones of vegetation: an outermost herb mat, typically comprised largely of Heliotropium anomalum; an inward zone of shrub, primarily Tournefortia argentea; and a central forested region, typically dominated by groves of Pisonia grandis trees. Coconut palms have also been introduced and exist in substantial quantities on the larger islets. This pattern of vegetation is consistent across the larger islets, with smaller islets lacking the central forest and the smallest vegetated solely by low herbs. Other common plants include Messerschmidia argentea, Suriana, and Morinda citrifolia.
Caroline Island is an important breeding site for a number of species of seabirds, most notably the Sooty Tern (Onychoprion fuscata), numbering around 500,000 – a colony of Sooty Terns dominates the eastern islets – and the Great Frigatebird (Fregata minor), numbering over 10,000. Caroline Island and its neighbor, Flint Island, also host some of the world's largest populations of the coconut crab. (Birgus latro). Other native animals include the Tridacna clam, which is abundant in the central lagoon, hermit crabs, and multiple species of lizards.
The endangered green sea turtle (Chelonia mydas) nests on the beaches of Caroline Island, but there have been reports of poaching by recent homesteaders. The Bristle-thighed Curlew (Numenius tahitiensis), a migrant visitor from Alaska, is also classified as vulnerable.
Around twenty non-native species of flora have been introduced to Caroline Island via human contact. Among these are the Ipomea tuba vine, which has begun to proliferate. Domestic cats and dogs introduced alongside a small homestead have driven the seabird population away from the islet of Monu Ata-Ata.
There is evidence of settlement by Polynesian peoples on the largest islets from before European contact. Graves and template platforms were uncovered by early expeditions to the island, and a large marae exists on the west side of Nake Islet. To date, these artifacts have not been surveyed by archaeologists.
The first recorded sighting of Caroline Island by Europeans was on February 21, 1606, by Pedro Fernández de Quirós, a Portuguese explorer sailing on behalf of Spain; his account names the island "San Bernardo." The atoll was "rediscovered" on December 16, 1795 by Captain William Robert Broughton of , who gave the atoll the name Carolina (which later became "Caroline") "in compliment to the daughter of Sir P. Stephens of the Admiralty." Caroline was again sighted in 1821 by the English whaling ship Supply and was then named "Thornton Island" for the ship's captain. Other early names for the atoll include Hirst Island, Clark Island, and Independence Island. Among other early visits which left behind accounts of the island are that of the USS Dolphin in 1825 (recorded by Lieutenant Hiram Paulding), and of a whaling ship in 1835 (recorded by Frederick Debell Bennett in his Narrative of a Whaling Voyage Round the Globe From the Year 1833–1836).
In 1846, the Tahitian firm of Collie and Lucett attempted to establish a small stock-raising and copra (coconut meat) community on the island, an operation which met with limited financial success. In 1868, Caroline was claimed by the British vessel HMS Reindeer, which noted 27 residents in a settlement on South Islet. This settlement lasted until 1904, when the 6 remaining Polynesians were relocated to Niue.
In 1872, the island was leased by the British government to Houlder Brothers, who conducted minimal guano mining on the island. In 1881, the lease was later taken over by the mining operation's manager, John T. Arundel (for whom one of the islets is named). Guano mining, which began in 1874, supplied a total of about 10,000 tons of phosphate until supplies were exhausted around 1895.
In 1883, an expedition of American astronomers traveled from Peru to Caroline Island aboard the USS Hartford to observe a total solar eclipse on May 6. A French expedition also observed the eclipse from Caroline, and the United States Navy mapped the atoll. Johann Palisa, a member of the expedition, discovered an asteroid later that year which he named Carolina "in remembrance of his visit to [the] island."
Caroline Island remained uninhabited and undisturbed through World War II and afterwards. It remained under British jurisdiction, repossessed by the British Western Pacific High Commission in 1943 and governed as part of the Central and Southern Line Islands. In January 1972, the Central and Southern Line Islands, including Caroline, were joined with the British colony of the Gilbert and Ellice Islands, which had become autonomous in 1971 as part of British decolonization efforts.
In 1979, the Gilbert Islands became the independent nation of Kiribati; Caroline Island was then and continues to be Kiribati's easternmost point. The entire island is presently owned by the government of the Republic of Kiribati, overseen by the Ministry of Line and Phoenix Groups, which is headquartered on Kiritimati. Competing claims to sovereignty over the island by the United States (under the Guano Islands Act) were relinquished in the 1979 Treaty of Tarawa, ratified by the U.S. Senate in 1983.
The island was briefly inhabited again from 1987 to 1991 by Ron Falconer, his wife Anne, and their two children, who developed a largely self-sufficient settlement on the atoll. Following a transfer of ownership, Falconer was evicted from the island by the Kiribati government. A book, Together Alone (ISBN 1-86325-428-5), written by Falconer, documents the story of their residence on Caroline Island. Jim Phillips of Hawaii and Sally Seesay of the Gambia inhabited the island for 5 months in last half of 1992, rejuvenating Falconer's homesite while staying on their yacht "Satisfaction" most of the time. That story is yet to be written.
In the 1990s, the island was leased to Urima Felix, a French Polynesian entrepreneur; he established a small homestead on one of the islets and reportedly had plans for development of the atoll. The island is also occasionally visited by Polynesian copra gatherers under agreements with the Kiribati government in Tarawa.
On December 23, 1994, the Republic of Kiribati announced a change of time zone for the Line Islands, to take effect January 1, 1995. This adjustment effectively moved the International Date Line over 1000 kilometers (600 mi) to the east within Kiribati, placing all of Kiribati on the Asian or western side of the date line, despite the fact that Caroline's longitude of 150 degrees west corresponds to UTC−10 rather than its official time zone of UTC+14. Caroline Island now is at the same time as the Hawaiian Islands (Hawaii-Aleutian Standard Time Zone), but one day later. This move made Caroline Island both the easternmost land in the earliest time zone (by some definitions, the easternmost point on Earth), and one of the first points of land which would see sunrise on January 1, 2000 — at 5:43 a.m., as measured by local time.
The stated reason for the move was a campaign promise of Kiribati President Teburoro Tito to eliminate the confusion of Kiribati straddling the Date Line and therefore being constantly in two different days. However, Kiribati officials were not reluctant to attempt to capitalize on the nation's new status as owners of the first land to see sunrise in 2000. Other Pacific nations, including Tonga and New Zealand's Chatham Islands, protested the move, objecting that it infringed on their claims to be the first land to see dawn in the year 2000.
In 1999, in order to further capitalize upon the massive public interest in celebrations marking the arrival of the year 2000, Caroline Island was officially renamed Millennium Island. Although uninhabited, a special celebration was held on the island, featuring performances by Kiribati native entertainers and attended by Kiribati president Tito. Over 70 Kiribati singers and dancers traveled to Caroline from the capital Tarawa, accompanied by approximately 25 journalists. The celebration, broadcast by satellite worldwide, had an estimated audience of up to one billion viewers.
Despite many media and government claims to the contrary, Caroline Island was not the first point of land to see sunrise on January 1, 2000 (local time); that distinction belongs to a point of land between Dibble Glacier and Victor Bay on the coast of East Antarctica, at , where the sun rose 35 minutes earlier. As this point is close to the Antarctic Circle, and the area beyond the Antarctic Circle is affected by the continuous sunlight in December, the definition of the exact point becomes a question of distinguishing between a sunset and an immediate sunrise in view of atmospheric refraction effects.