 The Northwestern Hawaiian Islands form part of theHawaiian island chain | |
  NW Hawaiian Islands Location of the Northwestern Hawaiian Islands in the Pacific Ocean Show map of Pacific Ocean NW Hawaiian Islands NW Hawaiian Islands (Hawaiian Islands) Show map of Hawaiian Islands | |
| Geography | |
|---|---|
| Location | Pacific Ocean |
| Coordinates | 25°N168°W / 25°N 168°W /25; -168 |
| Archipelago | Hawaiian Islands |
| Adjacent to | Pacific Ocean |
| Administration | |
| State/Territory | Hawaii andMidway Island |
TheNorthwestern Hawaiian Islands, also known as theLeeward Hawaiian Islands, are a series of mostly uninhabitedislands andatolls located northwest ofKauai andNiʻihau in theHawaiian island chain. Politically, these islands are part ofHonolulu County in theU.S. state ofHawaii, with the exception ofMidway Atoll, though they are generally not included on maps and graphic depictions of the State of Hawaii. Midway Atoll is aterritory distinct from the State of Hawaii, and is classified as one of theUnited States Minor Outlying Islands.[1] TheUnited States Census Bureau designates this area, excluding Midway Atoll, as Census Tract 114.98 of Honolulu County. The total land area of these islands is 3.1075 square miles (8.048 km²). With the exception ofNīhoa, all of the islands lie north of theTropic of Cancer, making them the only islands in Hawaii situated outside thetropics.
Almost all of the islands are uninhabited, the main exception being Midway Atoll, which maintains a permanent rotating population ofU.S. Fish and Wildlife Service staff and other workers.Kure Atoll andTern Island have a seasonal population of a small team of environmental staff. At least some of the islands were visited byAncient Hawaiians, with Nīhoa showing evidence of permanent habitation.
The Northwestern Hawaiian Islands are part of thePapahānaumokuākea Marine National Monument, a globally significant marine conservation area. They are home to endangered species like the Hawaiian monk seal and green sea turtle and hold cultural importance for Native Hawaiians. Geologically, they are the oldest in the Hawaiian-Emperor seamount chain, shaped by volcanic activity and erosion over millions of years.
The Northwestern or Leeward Hawaiian Islands include
Other islands or reefs were previously mapped as part of this chain but are now considered to be eitherphantom islands or misidentifications of existing islands. The following reefs continued to appear on maps as late as 1934:[3]
As late as 1960, a German globe showed islands west of Kure Atoll that had long been proven nonexistent:[citation needed]
The Northwestern Hawaiian Islands were formed approximately 7 to 30 million years ago, asshield volcanoes over the same volcanichotspot that formed theEmperor Seamounts to the north and the Main Hawaiian Islands to the south.[7] As thePacific Plate moved north and later northwest over the hot spot,volcanic eruptions built up islands in a linear chain. The isolated land masses gradually eroded and subsided, evolving from high islands in the south, much like the Main Islands of Hawaii, toatolls (orseamounts) north of theDarwin Point. Each of the NWHI are in various stages of erosion.Nīhoa,Necker, andGardner Pinnacles are rocky,basalt islands that have not eroded enough to form an atoll, or that lack a substantial coral reef.Laysan andLisianski are low, sandy islands that have been eroded longer.French Frigate Shoals,Pearl and Hermes,Midway, andKure are atolls.
North of the Darwin Point, the coral reef grows more slowly than the island's subsidence, and as the Pacific Plate moves northwest, the island becomes a seamount when it crosses this line. Kure Atoll straddles the Darwin Point, and will sink beneath the ocean when its coral reef cannot keep up with the rate of subsidence, a destiny that awaits every Hawaiian island.[8]
The Hawaiian Islands are about 2,500 miles (4,000 km) from North America and 3,800 miles (6,100 km) from Asia, and it is because of this isolation that the Hawaiian Islands have extraordinary numbers of unique species.[9] Only a species that could fly or swim immense distances could reach the archipelago. But whereas Polynesians, and later, Europeans, have largely altered the ecosystem of the Main Hawaiian islands by introducing alien species, the ecosystems of the NWHI remain, for the most part, intact. The extensive coral reefs found in Papahānaumokuākea are home to over 7,000 marine species.[10] Of the manyspecies that live here, over 1,700 species of organisms areendemic to the Hawaiian Islands (i.e., they are found nowhere else). For this reason, the region has been dubbed "America'sGalápagos".
Though not subject to nearly as muchextinction as the main islands, the Leeward Islands have had their share of abuse. From the late 19th to the early 20th centuries, fishermen,guano miners, and feather hunters killed most of the birds and sea life living in the NWHI. Rabbits were introduced to Laysan and Lisianski, where they multiplied and devoured most of the vegetation, permanently extinguishing several species. However, most of the damage was reversed, and the islands were restored largely to their pre-exploitation state.
The NWHI has been recognized as anImportant Bird Area (IBA) byBirdLife International because of its seabirds and endemic landbirds. Theseabirdcolonies in the IBA form one of the largest assemblages of tropical seabirds in the world, with over 14 million birds of 21 species.[11]
Some of the endemic species of the NWHI include theNīhoa andLaysan finch, theLaysan duck (the "rarest native waterfowl in the United States"),[12] and theNīhoa fan palm. Other notable species are theLaysan albatross, the highly endangeredHawaiian monk seal, and thegreen sea turtle. The only nativetrapdoor spiders in the Hawaiian archipelago (Nihoa spp.), recently discovered, are found here. Most endemic species are highly vulnerable to extinction as one major catastrophic event could wipe out all of the vegetation on each small island. Additionally, seventy percent of all coral reefs in the United States are found here.
The Northwestern Hawaiian Islands have a dry-summer tropical savannah climate,As in theKöppen climate classification system. In the driest month (May), they receive less than 60 mm (2.4 in) of precipitation and also less than mm of precipitation. These are the absolute and relative thresholds separating a tropical savanna climate from a tropical monsoon or rainforest climate.[13][14]
Because of their small size, rainfall and temperature are more consistent across and within these islands than in the larger Windward Islands (the main islands) of Hawaii. The sea swell is much larger in the winter. Total precipitation averages about 500 to 750 millimeters (20 to 30 inches) per year.[15]
| Climate data for Northwestern Hawaiian Islands Marine National Monument | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Mean daily maximum °C (°F) | 74 (23) | 73 (23) | 73 (23) | 76 (24) | 78 (26) | 82 (28) | 85 (29) | 86 (30) | 85 (29) | 82 (28) | 79 (26) | 75 (24) | 79.9 (26.6) |
| Daily mean °C (°F) | 70 (21) | 69 (21) | 69.5 (20.8) | 72 (22) | 74 (23) | 78.5 (25.8) | 81 (27) | 82 (28) | 81 (27) | 78.5 (25.8) | 75 (24) | 71 (22) | 75.5 (24.2) |
| Mean daily minimum °C (°F) | 66 (19) | 65 (18) | 66 (19) | 68 (20) | 70 (21) | 75 (24) | 77 (25) | 78 (26) | 77 (25) | 75 (24) | 71 (22) | 67 (19) | 71.3 (21.8) |
| Average rainfall mm (inches) | 2.52 (64) | 2.22 (56) | 1.64 (42) | 1.10 (28) | 0.91 (23) | 1.19 (30) | 1.72 (44) | 1.74 (44) | 2.53 (64) | 1.97 (50) | 2.62 (67) | 2.52 (64) | 22.68 (576) |
| Average rainy days | 11 | 9 | 9 | 7 | 6 | 6 | 8 | 8 | 9 | 8 | 10 | 11 | 102 |
| Averagerelative humidity (%) | 76 | 75 | 75 | 75 | 75 | 77 | 77 | 76 | 76 | 76 | 76 | 76 | 75.8 |
| Source:Time and Date | |||||||||||||
Archeological evidence suggestsancient Hawaiians visited but did not live on Mokumanamana (Necker) and French Frigate Shoals, and the islands were deserted when Europeans arrived in the 18th century. Agricultural terraces indicate Hawaiians lived on Nīhoa for extended periods of time. Mokumanamana lacks vegetation and is unsuitable for agriculture, and archeological studies indicate early Hawaiians only visited and used the island for religious purposes.
The first of the Leeward Isles to be discovered by Europeans was Nīhoa.James Colnett discovered it in 1786, although historically the credit has gone to William Douglas. Later that year,La Pérouse discovered Necker, and named it forJacques Necker, the French Minister of Finance. La Pérouse then went on to discover French Frigate Shoals. The last of the NWHI to be discovered was Midway Atoll, which was found by N.C. Middlebrooks in 1859. In 1925, theTanager Expedition travelled to many of the NWHI. The islands were mapped, new species were discovered and described, and the archeological sites on Nīhoa and Necker were found.
Most of the islands have several names: one in English and one or more in Hawaiian (indicated in parentheses above). The majority of the Hawaiian names used as alternatives to the English ones were created in modern times; the original names that ancient Hawaiians gave to all of these islands that they encountered prior to Western contact are found in various oli (chants) and moʻolelo (stories).
On June 15, 2006, American PresidentGeorge W. Bush issued a public proclamation creatingPapahānaumokuākea Marine National Monument under theAntiquities Act of 1906. The Monument encompasses the islands and surrounding waters, forming the largest marine wildlife reserve in the world. PresidentTheodore Roosevelt had declared the Northwestern Hawaiian chain a bird sanctuary in 1909, and the islands had been protected since 2000 with a designation as an 'ecosystem reserve' by PresidentBill Clinton, but increasing it to national monument status provides unprecedented control. 139,000 square miles (360,000 km2) of ocean was at that time set aside for protection, about the size of the U.S. state ofCalifornia.
In August 2016, PresidentBarack Obama expanded the area of the monument by roughly four times. The expanded monument was at that time the world's largestmarine protected area.[16][17]
Entry to the Monument is limited through a permit system, jointly administered byNOAA,FWS, and the state ofHawaii. Anyone who comes to the islands must follow stringent procedures designed to prevent any stray species from entering and disrupting the ecosystem. All clothes must be bought new, and kept wrapped until before arrival. In fact, all "soft" items (camera strap, blanket) must be bought new, and all "hard" items (camera, binoculars) must be cleaned thoroughly. Then, every item must be frozen for 48 hours. A new set of equipment must be prepared for each island one is going to, to prevent inter-island species introduction. However, French Frigate Shoals and Midway Atoll are exempted from these rules, as they are deemed too altered by humans already to worry about introducing new species.
State ofHawaii | |
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Honolulu (capital) | |
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| Main islands | |
| Northwestern Islands | |
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| International | |
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| National | |
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