Geography of Tuvalu

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The Western Pacific nation of Tuvalu, formerly known as the Ellice Islands, is situated 4,000 kilometers (2,500 mi) northeast of Australia and is approximately half way between Hawaii and Australia. Tuvalu consists of three reef islands and six atolls. The islands of Tuvalu have poor soil and a total land area of only about 26 km², less than 10 sq mi (30 km2). The land is very low-lying, with narrow coral atolls. The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita.

Tuvalu experiences two distinct seasons, a wet season from November to April and a dry season from May to October.[1] Westerly gales and heavy rain are the predominate weather conditions from October to March, the period that is known as Tau-o-lalo, with tropical temperatures moderated by easterly winds from April to November.

Geography

Location: Oceania, island group of nine islands comprising three reef islands and six true atolls in the South Pacific Ocean.[2] The islands of Tuvalu are spread out between the latitude of to 10° south and longitude of 176° to 180°, west of the International Date Line.[3]

Map of Tuvalu

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Map references: Oceania

Area:
total: 26 km²
land: 26 km²
water: 0 km²

Area - comparative: 0.1 times the size of Washington, DC

Land boundaries: 0 km

Coastline: 24 kilometres (15 mi)

Maritime claims:
contiguous zone: 24 nmi (44 km)
exclusive economic zone: 200 nmi (370 km)
territorial sea: 12 nmi (22 km)

Tuvalu’s Exclusive Economic Zone (EEZ) covers an oceanic area of approximately 900,000 km2.[4]

On 29 August 2012 an Agreement between Tuvalu and Kiribati concerning their Maritime Boundary, was signed by their respective leaders that determined the boundary as being seaward of Nanumea and Niutao in Tuvalu on the one hand and Tabiteuea, Tamana and Arorae in Kiribati on the other hand, along the geodesics connecting the points of latitude and longitude set out in the agreement.[5]

In October 2014 the prime ministers of Fiji and Tuvalu signed the Fiji-Tuvalu Maritime Boundary Treaty, which establishes the extent of the national areas of jurisdiction between Fiji and Tuvalu as recognized in international law under the 1982 United Nations Convention on the Law of the Sea.[6]

Climate: tropical; moderated by easterly trade winds (March to November); westerly gales and heavy rain (November to March).

Terrain: low-lying and narrow coral atolls.

Elevation extremes:
lowest point: Pacific Ocean 0 m
highest point: unnamed location, 4.6 metres (15 ft) on Niulakita.

Extreme points:

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This is a list of the extreme points of Tuvalu, the points that are farther north, south, east or west than any other location:

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Natural resources: fish

Land use:
arable land: 0%
permanent crops: 60%
other: 40% (2011)

Irrigated land: NA km²

Native broadleaf forest

Fualefeke Islet

The islets of the Funafuti Conservation Area have 40% of the remaining native broadleaf forest on Funafuti atoll. While Coconut palms are common in Tuvalu, they are usually cultivated rather than naturally seeding and growing. Tuvaluan traditional histories are that the first settlers of the islands planted Coconut palms as they were not found on the islands. The native broadleaf forest of Funafuti would include the following species, that were described by Charles Hedley in 1896,[7] which include the Tuvaluan name (some of which may follow Samoan plant names):

The blossoms that are valued for their scent and for use in flower necklaces and headdresses include: Fetau, (Calophyllum inophyllum); Jiali, (Gardenia taitensis); Boua (Guettarda speciosa); and Crinum.[7]

Charles Hedley (1896) identified the uses of plants and trees from the native broadleaf forest as including:[8]

Thaman (1992) provides an literature review of the ethnobiology of the Pacific Islands.[9]

Climate & natural hazards

El Niño and La Niña

Tuvalu experiences the effects of El Niño and La Niña that flow from changes in ocean temperatures in equatorial and central Pacific. El Niño effects increase the chances of tropical storms and cyclones; while La Niña effects increase the chances of drought conditions in Tuvalu.[10] On 3 October 2011, drought conditions resulted in a state of emergency being declared as water reserves ran low.[11][12][13] Typically the islands of Tuvalu receive between 200mm to 400mm of rainfall per month, however a weak La Niña effect causes a drought by cooling the surface of the sea around Tuvalu.[10]

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Tropical cyclones

Severe tropical cyclones are usually rare, however the low level of islands makes them very sensitive to sea-level rise. George Westbrook, a trader on Funafuti, recorded a cyclone that struck Funafuti in 1883.[14] A cyclone caused severe damage to the islands in 1894.[15]

Cyclone Bebe caused severe damage to Funafuti during the 1972-1973 cyclone season. Funafuti’s Tepuka Vili Vili islet was devastated by Cyclone Meli in 1979, with all its vegetation and most of its sand swept away during the cyclone.[16] Cyclone Gavin was first identified during 2 March 1997, and was the first of three tropical cyclones to affect Tuvalu during the 1996-97 cyclone season with Cyclones Hina and Keli following later in the season. Cyclone Ofa had a major impact on Tuvalu in late January and early February 1990.[17][18][19] On Vaitupu Island around 85 percent of residential homes, trees and food crops were destroyed, while residential homes were also destroyed on the islands of Niutao, Nui and Nukulaelae.[19] The majority of the islands in Tuvalu reported damage to vegetation and crops especially bananas, coconuts and breadfruit, with the extent of damage ranging from 10 to 40 percent. In Funafuti sea waves flattened the Hurricane Bebe bank at the southern end of the airstrip, which caused sea flooding and prompted the evacuation of several families from their homes. In Nui and Niulakita there was a minor loss of the landscape because of sea flooding while there were no lives lost. Soon after the systems had impacted Tuvalu, a Disaster Rehabilitation Sub-Committee was appointed to evaluate the damage caused and make recommendations to the National Disaster Committee and to the Cabinet of Tuvalu, on what should be done to help rehabilitate the affected areas.[19]

In March 2015 Cyclone Pam, the Category 5 cyclone that devastated Vanuatu, caused damage to houses, crops and infrastructure on the outer islands.[20][21][22][23] A state of emergency was subsequently declared on March 14.[24] An estimated 45 percent of the nation's nearly 10,000 people were displaced, according to Prime Minister Enele Sopoaga.[25][26] The three northern islands, Nanumea, Nanumaga and Niutao were badly affected by flooding as the result of storm surges. More than 400 people from the northern island of Nanumaga were moved to emergency accommodation in the school buildings, as well as another 85 families from Nukulaelae in the south of Tuvalu. On Nui the storm surges contaminated the water supplies and damaged septic tanks and grave sites. The central islands of Vaitupu and Nukufetau were also affected by flooding caused by storm surges.[27][28][29] The Situation Report published on 30 March reported that on Nukufetau all the displaced people have returned to their homes.[30]

Nui suffered the most damage of the three central islands (Nui, Nukufetau and Vaitupu);[31] with both Nui and Nukufetau suffering the loss of 90% of the crops.[30] Of the three northern islands (Nanumanga, Niutao, Nanumea), Nanumanga suffered the most damage, with 60-100 houses flooded and damage to the health facility.[30][32] Vasafua islet, part of the Funafuti Conservation Area, was severely damaged by Cyclone Pam. The coconut palms were washed away, leaving the islet as a sand bar.[33][34]

Tsunami

Nui was struck by a giant wave on 16 February 1882;[35] earthquakes and volcanic eruptions occurring in the basin of the Pacific Ocean and along the Pacific Ring of Fire are a possible cause of a Tsunami. There is earthquake activity in the Solomon Islands, where earthquakes occurred along the boundary of the Pacific plate with, respectively, the Indo-Australia, Woodlark, and Solomon Sea plates.[36]

Environment

Island, reef and lagoon habitats

Funafuti atoll.

Tuvalu consists of three reef islands and six true atolls. Its small, scattered group of atolls have poor soil and a total land area of only about 26 square kilometres (less than 10 sq. mi.) making it the fourth smallest country in the world. The islets that form the atolls are very low-lying. Nanumaga, Niutao, Niulakita are reef islands and the six true atolls are Funafuti, Nanumea, Nui, Nukufetau, Nukulaelae and Vaitupu. Funafuti is the largest atoll of the nine low reef islands and atolls that form the Tuvalu volcanic island chain. It comprises numerous islets around a central lagoon that is approximately 25.1 kilometres (15.6 mi) (N–S) by 18.4 kilometres (11.4 mi) (W-E), centred on 179°7’E and 8°30’S. On the atolls an annular reef rim surrounds the lagoon, with several natural reef channels.[37] A standard definition of an atoll is "an annular reef enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus".[37]

The eastern shoreline of Fongafale in the Funafuti Lagoon was modified during World War II; several piers were constructed, beach areas filled, and deep water access channels were excavated. These alternations to the reef and shoreline have resulted in changes to wave patterns with less sand accumulating to form the beaches as compared to former times; and the shoreline is now exposed to wave action.[38] Several attempts to stabilize the shoreline have not achieved the desired effect.[39]

The rising population results in increased demand on fish stocks, which are under stress;[40] although the creation of the Funafuti Conservation Area has provided a fishing exclusion area that helps sustain fish populations across the Funafuti lagoon. Population pressure on the resources of Funafuti and in-adequation sanitation systems have resulted in pollution.[41][42] The Waste Operations and Services Act 2009 provides the legal framework for the waste management and pollution control projects funded by the European Union that are directed to organic waste composting in eco-sanitation systems.[43] Plastic waste is also a problem as much imported food and other commodities is supplied in plastic containers or packaging.

Surveys were carried out in May 2010 of the reef habitats of Nanumea, Nukulaelae and Funafuti (including the Funafuti Conservation Area) and a total of 317 fish species were recorded during this Tuvalu Marine Life study. The surveys identified 66 species that had not previously been recorded in Tuvalu, which brings the total number of identified species to 607.[44][45]

Environment - climate change issues

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Since there are no streams or rivers and groundwater is not potable, most water needs must be met by catchment systems with storage facilities; beachhead erosion because of the use of sand for building materials; excessive clearance of forest undergrowth for use as fuel; damage to coral reefs from the bleaching of the coral as a consequence of the increase of the ocean temperatures and acidification from increased levels of carbon dioxide; Tuvalu is very concerned about global increases in greenhouse gas emissions and their effect on rising sea levels, which threaten the country's underground water table. Tuvalu has adopted a national plan of action as the observable transformations over the last ten to fifteen years show Tuvaluans that there have been changes to the sea levels.[46]

Because of the low elevation, the islands that make up this nation are threatened by current and future sea level rise.[41][47] The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita,[48] which gives Tuvalu the second-lowest maximum elevation of any country (after the Maldives). However, the highest elevations are typically in narrow storm dunes on the ocean side of the islands which are prone to over topping in tropical cyclones, such as occurred on Funafuti with Cyclone Bebe.[49]

Ocean side of Funafuti atoll showing the storm dunes, the highest point on the atoll.

Tuvalu is mainly composed of coral debris eroded from encircling reefs and pushed up onto the islands by winds and waves.[50] Paul Kench at the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji released a study in 2010 on the dynamic response of reef islands to sea level rise in the central Pacific. Tuvalu was mentioned in the study, and Webb and Kench found that seven islands in one of its nine atolls have spread by more than 3 per cent on average since the 1950s.[51] One island, Funamanu, gained 0.44 hectares, or nearly 30 per cent of its previous area. In contrast, Tepuka Vili Vili has suffered a net loss in area of 22 percent since 1896. The shape and orientation of the reef has also changed over time.[50]

The storm surge resulting from a tropical cyclone can dramatically shift coral debris. In 1972 Funafuti was in the path of Cyclone Bebe. Tropical Cyclone Bebe was a pre-season tropical cyclone that impacted the Gilbert, Ellice Islands, and Fiji island groups.[52] The storm surge created a wall of coral rubble along the ocean side of Fongafale and Funafala that was about 10 miles (16 km) long, and about 10 feet (3.0 m) to 20 feet (6.1 m) thick at the bottom.[53] The cyclone knocked down about 90% of the houses and trees on Funafuti and contaminated sources of drinking water as a result of the system's storm surge and fresh water flooding.

Tuvalu is affected by perigean spring tide events which raise the sea level higher than a normal high tide.[54] The highest peak tide recorded by the Tuvalu Meteorological Service was 3.4 metres (11 ft) on 24 February 2006 and again on 19 February 2015.[55][56] As a result of historical sea level rise, the king tide events lead to flooding of low-lying areas, which is compounded when sea levels are further raised by La Niña effects or local storms and waves. In the future, sea level rise may threaten to submerge the nation entirely as it is estimated that a sea level rise of 20–40 centimetres (8–16 inches) in the next 100 years could make Tuvalu uninhabitable.[57][58]

A wharf and beach at Funafuti atoll

Tuvalu experiences westerly gales and heavy rain from October to March - the period that is known as Tau-o-lalo; with tropical temperatures moderated by easterly winds from April to November. Drinking water is mostly obtained from rainwater collected on roofs and stored in tanks; these systems are often poorly maintained, resulting in lack of water.[59] Aid programs of Australia and the European Union have been directed to improving the storage capacity on Funafuti and in the outer islands.[60]

The reefs at Funafuti have suffered damage, with 80 per cent of the coral having been bleached as a consequence of the increase of the ocean temperatures and acidification from increased levels of carbon dioxide.[40][61] The coral bleaching, which includes staghorn corals, is attributed to the increase in water temperature that occurred during the El Niños that occurred from 1998–2000 and from 2000–2001.[62] Researchers from Japan have investigated rebuilding the coral reefs through introduction of foraminifer.[63]

Borrow Pits Remediation (BPR) project

When the airfield, which is now Funafuti International Airport, was constructed during World War II. The coral base of the atoll was used as fill to create the runway. The resulting borrow pits impacted the fresh-water aquifer. In the low areas of Funafuti the sea water can be seen bubbling up through the porous coral rock to form pools with each high tide.[64][65][66] Since 1994 a project has been in development to assess the environmental impact of transporting sand from the lagoon to fill all the borrow pits and low-lying areas on Fongafale.[67] In 2013 a feasibility study was carried out and in 2014 the Tuvalu Borrow Pits Remediation (BPR) project was approved, which will result in all 10 borrow pits being filled, leaving Tafua Pond, which is a natural pond.[68] The New Zealand Government funded the BPR project.[69] The project was carried out in 2015 with 365,000 sqm of sand being dredged from the lagoon to fill the holes and improve living conditions on the island. This project increase the useable land space on Fongafale by eight per cent.[70]

Environment - international agreements


Tuvalu is a party to: Biodiversity, Climate Change, Climate Change-Kyoto Protocol, Desertification, Law of the Sea, Ozone Layer Protection, Ship Pollution, Whaling
signed, but not ratified: none

Aquifer salinization issues

Aquifer salinization of Fongafale Islet, Funafuti

The investigation of groundwater dynamics of Fongafale Islet, Funafuti, show that tidal forcing results in salt water contamination of the surficial aquifer during spring tides.[71] The degree of aquifer salinization depends on the specific topographic characteristics and the hydrologic controls in the sub-surface of the atoll. About half of Fongafale islet is reclaimed swamp that contains porous, highly permeable coral blocks that allow the tidal forcing of salt water.[72] There was extensive swamp reclamation during World War II to create the air field that is now the Funafuti International Airport. As a consequence of the specific topographic characteristics of Fongafale, unlike other atoll islands of a similar size, Fongafale does not have a thick freshwater lens.[72] The narrow fresh water and brackish water sheets in the sub-surface of Fongafale islet results in the taro swamps and the fresh groundwater resources of the islet being highly vulnerable to salinization resulting from the rising sea-level.[72]

In addition to the increased risk of salinized by the sea-level rise, the freshwater lens is at risk from over extraction due to the large population that now occupies Fongafale islet; the increased extraction can be exacerbated by a decrease of the rainfall recharge rate associated with the climate change.[71] Water pollution is also a chronic problem, with domestic wastewater identified as the primary pollution source.[73] Approximately 92% of households on Fongafale islet have access to septic tanks and pit toilets. However these sanitary facilities are not built as per the design specifications or they are not suitable for the geophysical characteristics, which results in seepage into the fresh water lens and run off into coastal waters.[73]

On Funafuti and on the other islands, rainwater collected off the corrugated iron roofs of buildings is now the primary source of fresh water. On Funafuti a desalination unit that was donated by Japan in 2006 also provides fresh water.[74] In response to the 2011 drought, Japan funded the purchase of a 100 m³/d desalination plant and two portable 10 m³/d plants as part of its Pacific Environment Community (PEC) program.[75][76] Aid programs from the European Union[77][60] and Australia also provided water tanks as part of the longer term solution for the storage of available fresh water.[78]

Aquifer salinization and the impact on Puluka production

Swamp taro (Cyrtosperma chamissonis), known in Tuvalu as Pulaka, is grown in large pits of composted soil below the water table,[79] Pulaka has been the main source for carbohydrates,[79] it is similar to taro, but "with bigger leaves and larger, coarser roots".[80]

In recent years the Tuvaluan community have raised concerns over increased salinity of the groundwater in pits that are used to cultivate pulaka.[81] Pits on all islands of Tuvalu (except Niulakita) were surveyed in 2006. Nukulaelae and Niutao each had one pit area in which salinity concentrations thought to be too high for successful swamp taro growth. However, on Fongafale in Funafuti all pits surveyed were either too saline or very marginal for swamp taro production, although a more salt tolerant species of taro (Colocasia esculenta) was being grown in Fongafale.[82]

The extend of the salinization of the aquifer on Fongafale Islet is the result of both man-made changes to the topographic that occurred when the air field was built in World War II by reclaiming swamp land and excavating coral rock from other parts of the islet. These topographic changes are exacerbated by the groundwater dynamics of the islet, as tidal forcing pushes salt water into the surficial aquifer during spring tides.[71]

The freshwater lens of each atoll is a fragile system. Tropical cyclones and other storm events also result in wave wash over and extreme high water also occurs during spring tides. These events can result in salt water contamination of the fresh groundwater lens. Periods of low rainfall can also result in contraction of the freshwater lens as the coconut trees and other vegetation draw up the water at a greater than recharge than it can be recharged. The over extraction of ground water to supply human needs has a similar result as drought conditions.[83]

References

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