Caroline Island
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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 the 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 which is 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.
Flora and fauna