Bikar Atoll
Bikar Atoll is a small and remote coral atoll located in the northernmost region of the Marshall Islands, approximately 360 miles north of Majuro, the capital. Formed from the fringing reef of an extinct volcano, Bikar features a continuous reef surrounding a lagoon that spans about 14 square miles, while the land area of its islets is only around 0.2 square miles. The atoll is characterized by a warm, semiarid climate with limited freshwater resources, contributing to its sparse human settlement. Despite some fishing activity, Bikar is known for its relatively undisturbed ecosystem, which includes a variety of flora and fauna, such as endemic bird species and the endangered green turtle, which uses the atoll as a nesting ground.
However, Bikar is not without its environmental challenges. The introduction of invasive black rats poses a threat to native wildlife, and the soil has been contaminated with nuclear fallout from past U.S. nuclear tests. The atoll's coral reefs support various marine life but face risks from climate change, including rising sea levels and increased cyclone activity. As a part of the larger Marshall Islands, Bikar is included in significant conservation efforts, such as a shark sanctuary aimed at preserving the health of its marine ecosystems. Bikar Atoll exemplifies the delicate balance between natural beauty and environmental vulnerability characteristic of many small, isolated islands in the Pacific.
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Bikar Atoll
- Category: Marine and Oceanic Biomes.
- Geographic Location: Pacific Ocean.
- Summary: Bikar is a small, remote coral atoll in the Marshall Islands, known for its relatively undisturbed and pristine flora and fauna.
The Bikar Atoll is among the northernmost of the Marshall Islands, a sparsely inhabited republic of twenty-nine coral atolls and five islands situated in the tropical North Pacific Ocean, approximately 2,000 miles (3,400 kilometers) northeast of Papua New Guinea, 2,800 miles (4,600 kilometers) southeast of Japan, and 2,500 miles (4,100 kilometers) west of Hawaii. Like most atolls, Bikar was formed as the fringing reef of a now-extinct basaltic volcano, which has since subsided into the ocean, leaving a ring of small islets.
The small area, lack of freshwater, and remote location of Bikar Atoll contribute to the lack of any permanent human settlement. Though some fishing pressure exists on and around Bikar, the flora and fauna here have remained relatively pristine and undisturbed throughout history. Even this remote location is not immune to all human influence, however, as the Bikar islets, which are home to a native population of Polynesian rats (Rattus exulans), have been impacted by invasive black rats (Rattus rattus) from fishing vessels; the invasive rat species, which is more aggressive and carnivorous, poses a threat to seabird and turtle nesting sites. Also, the soil of Bikar was contaminated with nuclear fallout from the 1954 Castle Bravo nuclear test conducted by the United States in Bikini Atoll, some 300 miles (485 kilometers) upwind.
Bikar Atoll is one of the smallest atolls in the Republic of the Marshall Islands (RMI), and is located roughly 360 miles (580 kilometers) north of Majuro Island, the capital of the RMI. The diamond-shaped fringing reef of the atoll is continuous except for a single narrow, forked passage. The reef encloses a lagoon covering roughly 14 square miles (37 square kilometers), though the combined land area of its handful of islets is only about 0.2 square mile (0.5 square kilometer). The largest of these, also called Bikar, reaches a height of 20 feet (6 meters) above sea level, common across the RMI. Though direct measurements have never been taken, evidence from nearby similar atolls indicates that the fringing reef may extend as much as 4,600 feet (1,402 meters) beneath the ocean surface and be approximately 55 million years old. The islets and atoll have built up around the central cone of an extinct volcano that rises more than 10,000 feet (3,048 meters) from the seafloor.
Bikar Atoll is relatively warm and semiarid, with an average air temperature of 82 degrees F (28 degrees C). Average annual precipitation is less than 45 inches (114 centimeters); most rain falls during the July-to-October wet season, and little freshwater is available.
Flora and Fauna
Flora on Bikar consists predominantly of atoll forest with scrub understory. The tough, spotty forest is largely made up of low, salt- and drought-resistant species common to the Indo-Pacific realms, such as Mapou (Myrsine australis), grand devil's claws (Pisonia grandis), and scattered screwpine (Pandanus tectorius). Tree heliotrope (Tournefortia argentea) plays an opportunistic role. Herbaceous plants, such as spiderlings (Boerhavia spp.), also occasionally make inroads. Some coconut palms originally introduced by visiting islanders are present, though such plants are periodically decimated by cyclone activity.
Bikar is a traditionally important nesting and feeding ground for several dozen species of birds, including frigatebirds such as the great frigatebird (Fregata minor), terns including the sooty tern (Onychoprion fuscatus), and boobies like the red-footed booby (Sula sula). The atoll is especially important as a nesting ground for the endangered green turtle (Chelonia mydas). Bikar is one of just three sites in the RMI deemed significant in this regard, and it is thought at various times to have hosted the largest number of green turtles in the Marshalls.
Beyond the islets and below the waves, the coral reef itself is a secondary harbor of life here, although not as abundantly blessed with species diversity as reefs in other biomes. Dozens of species of coral occur at Bikar, supporting various types of green, blue, and brown algae including the green macroalgae (Halimeda taenicola and Halimeda lacunalis), and mollusks like the bear claw clam (Hippopus maculatus). Drawing fishermen are the two-spot red snapper (Lutjanus bohar), humpback red snapper (Lutjanus gibbus), leopard grouper (Mycteroperca rosacea), and humphead parrotfish (Bolmetapan muricatus).
There is among the reef fishes a substantial variety of moray eel species, including the Seychelles moray eel (Anarchias seychellensis), yellow-edged moray (Gymnothorax flavimarginatus), giant moray (Gymnothorax javanicus), hookjaw moray (Enchelycore bayeri), viper moray (Enchelynassa canina), and snowflake moray (Echidna nebulosa).
Human Activity
The United States assumed ownership of the Marshall Islands at the close of World War II, and this area was the site of several nuclear tests during the 1950s, including the 1954 Castle Bravo nuclear test. That test near Bikini Atoll was well west of Bikar, but Bikar was directly in the fallout plume. The explosion left elevated levels of radiation in Bikar's soil for several decades, though a 1981 survey of fish caught in and around the Bikar lagoon showed minimally elevated levels of radiation at that time.
In 1986, the United States ended its territorial trusteeship over the Marshall Islands, transferring power to the RMI. The Marshalls remain under a Compact of Free Association with the United States.
In October 2011, the RMI government dedicated what is one of the world's most extensive shark sanctuaries, comprising 770,000 square miles (two million square kilometers) of ocean surrounding the Marshall Islands. A primary aim of the Marshall Islands National Shark Sanctuary is to protect the health of the reefs, as the shark population in its natural role controls the scope of the schools of other large predator fish, which in turn affect the types of small fish and other organisms that trim plankton blooms, clean corals, and otherwise maintain a balanced, healthy reef ecosystem.
Global climate change presents a fairly uniform threat to many atoll reef systems. The mean level of Bikar Atoll's lagoon is about 1.5 feet (0.5 meter) above the ocean level. Most of the coral lies below sea level, but some coral heads are situated above the shallow lagoon level. Complete inundation of these outposts is a very real possibility; however, saltwater intrusion is not a factor. A more pervasive effect is likely to be increased storm damage from cyclones, which already wreak considerable destruction upon the forests. Reef infrastructure will be more directly at risk from water-temperature rise, which has been indicated as a negative factor that has contributed to coral bleaching cases worldwide. The Marshall Islands have been subjected to "king tides," high tides that cause flooding. Because of rising water and tides, the US Geological Survey predicts that some of the Marshall Islands will be submerged by 2035.
Bibliography
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