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1 . Kiribati     Kiribati
Kiribati’s islands and coral reefs straddle a vast swathe of the Pacific Ocean but consist of only some 33 islands or island systems. These are typically divided into three broad groups. Most of the actual islands are now referred to by their Micronesian names, although the island groups are still largely referred to by their European names. In the far west is the long disparate chain of the Gilbert Islands or Tungaru Group – this is a chain of 11 atolls and five other islands which have no lagoon but are of similar origin. Often considered alongside this chain is the isolated island of Banaba, a raised atoll reaching a height of some 81 meters similar to Nauru (see below), and the only “high” island in the country. The Phoenix Islands include three atolls and five other islands with fringing reefs. There are also at least two other submerged reef structures (Winslow and Carondelet) which have no associated islands. The Line Islands in the east fall into a northern and southern group. The northern group includes the island of Teraina and the atolls of Tabuaeran and Kiritimati. The latter, pronounced Kirisimas and also known as Christmas Island, has a largely infilled lagoon and the largest land area of any atoll. The southern Line Islands are mostly uninhabited and include the atoll of Millennium Island (formerly Caroline Island) and three other islands with fringing reefs as well as at least one other submerged reef with no associated island. Lying on the equator, the country is largely unaffected by cyclones. The predominant climatic influence comes from the southeast trade winds which create a pronounced windward side to the reefs. The western islands are generally wetter, while the Line Islands lie in the dry equatorial zone. Rainfall is also significantly higher in all areas during El Niño Southern Oscillation events. Although tidal ranges tend to be low (less than 2 meters at spring tides) there is variation in sea level through the year (10-20 centimeters variation in mean monthly levels) which can be further exacerbated by up to 40 centimeters during El Niño years.

The atolls comprise a typical diversity of habitats, including channels, lagoon reefs and shallow reef flats as well as reef slope environments. There is a clear difference between windward and leeward sides, with the windward (eastern) sides typically having a continuous reef margin, narrow reef flat and well developed islands. The leeward reefs are typically much wider, but in some places show a more gradual slope with a less developed reef flat, often submerged at low tide. Spur and groove formations are on all sides, but are usually best developed on lee shores.

Given the wide geographic spread of this country it is possible to follow some of the wider regional trends within the country itself, notably the diminishing species diversity moving from west to east. Some 115 hard coral species have been recorded from Tarawa and Abaiang Atolls in the west, while Tabuaeran in the east has 71. Blue coral Heliopora coerulea is reported to be widespread in the west despite being uncommon over nearby areas in the Pacific. Coral cover on the outer reef slopes is typically very high, with measurements on Tarawa and Abaiang of up to 57 percent cover at 3 meters depth and 28-72 percent at 10 meters. Much of the remainder of the benthos is dominated by coralline algae. There are several very important seabird nesting colonies in the Phoenix and Line Islands, with many millions of birds, including the Phoenix petrel and the Polynesian storm-petrel.

The population of Kiribati is low and almost entirely concentrated in the Gilbert Islands. Elsewhere most of the islands are uninhabited, in many areas because freshwater is not always available. Most of the islanders are heavily dependent on fish as a source of protein, and overfishing is a localized problem near population centers. Reports of increasing incidence of ciguatera poisoning have been linked to other environmental disturbance including the dredging of channels and construction of causeways, although these links remain unproven. Locally, notably in the Tarawa lagoon, sewage pollution may be a problem. This has been exacerbated by the construction of causeways in this atoll to link the islands, which has altered circulation patterns in the lagoon and interrupted the migration patterns of spawning fish. Solid waste disposal is a problem in all areas. Despite being low, populations are now rapidly increasing and there are moves to settle some of the uninhabited islands in the Phoenix Group.
Source: Spalding, M.D., C. Ravilious and E.P. Green , 2001 , World Atlas of Coral Reefs . Prepared at the UNEP World Conservation Monitoring Centre. University of California Press,Berkeley,USA.421p. (See Document)

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