Geography of Tuvalu
The Western Pacific nation of Tuvalu, formerly known as the Ellice Islands, is situated 4,000 kilometers (2,500 mi) northeast of Australia. It is one half of the way from Hawaii to 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).
Tuvalu has westerly gales and heavy rain from November to March and tropical temperatures moderated by easterly winds from April to November. The land is very low-lying, with narrow coral atolls. The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita.
Location: Oceania, island group of nine islands comprising three reef islands and six true atolls in the South Pacific Ocean, about one-half of the way from Hawaii to Australia. The islands of Tuvalu are spread out between the latitude of 5° to 10° south and longitude of 176° to 180°, west of the International Date Line.
Map references: Oceania
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)
contiguous zone: 24 nmi (44 km)
exclusive economic zone: 200 nmi (370 km)
territorial sea: 12 nmi (22 km)
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
This is a list of the extreme points of Tuvalu, the points that are farther north, south, east or west than any other location.
- Northernmost point – Lakena island, Nanumea
- Easternmost point – Niuoko island, Nukulaelae
- Southernmost point – Niulakita
- Westernmost point - Lakena island, Nanumea
Natural resources: fish
arable land: 0%
permanent crops: 60%
other: 40% (2011)
Irrigated land: NA km²
Natural hazards: 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. A cyclone caused severe damage to the islands in 1894. Nui was struck by a giant wave on 16 February 1882; earthquakes and volcanic eruptions occurring in the basin of the Pacific Ocean - the Pacific Ring of Fire - are a possible cause of a Tsunami.
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. 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 January 1990. 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. 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.
Environment - current issues: 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.
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. On 3 October 2011, drought conditions resulted in a state of emergency being declared as water reserves ran low. Typically the islands of Tuvalu receive between 200mm to 400mm of rainfall per month, however a weak La Niña effect caused a drought by cooling the surface of the sea around Tuvalu.
Environment - international agreements:
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
Geography and environment
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. A standard definition of an atoll is "an annular reef enclosing a lagoon in which there are no promontories other than reefs and composed of reef detritus".
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.
Because of the low elevation, the islands that make up this nation are threatened by current and future sea level rise. The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita, 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.
Tuvalu is mainly composed of coral debris eroded from encircling reefs and pushed up onto the islands by winds and waves. 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. One island, Funamanu, gained 0.44 hectares, or nearly 30 per cent of its previous area. 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.
Tuvalu is affected by perigean spring tide events which raise the sea level higher than a normal high tide. 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.
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. Aid programs of Australia and the European Union have been directed to improving the storage capacity on Funafuti and in the outer islands.
The rising population results in increased demand on fish stocks, which are under stress; 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. 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. Plastic waste is also a problem as much imported food and other commodities is supplied in plastic containers or packaging.
When the airfield at Funafuti 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 on the water aquifer; at these pits the sea water can be seen bubbling up through the porous coral rock to form pools on each high tide. The eastern shoreline of Funafuti Lagoon was also 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. Several attempts to stabilize the shoreline have not achieved the desired effect.
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. 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. Researchers from Japan have investigated rebuilding the coral reefs through introduction of foraminifer.
Native broadleaf forest
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 settles 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, which include the Tuvaluan name (some of which may follow Samoan plant names):
- Fala or Screw Pine, (Pandanus)
- Pouka, (Hernandia peltata)
- Futu, (Barringtonia asiatica)
- Fetau, (Calophyllum inophyllum)
- Ferra, native fig, (Ficus aspem)
- Fau or Fo fafini, or woman's fibre tree (Hibiscus tiliaceus)
- Lakoumonong, (Wedelia strigulosa)
- Lou, (Cardamine sarmentosa)
- Meili fern, (Polypodium), another fern is Asplenium nidus
- Miro, (Thespesia populnea)
- Ngashu or Naupaka, (Scaevola kœnigii)
- Ngia or Ingia bush, (Pemphis acidula)
- Nonou, (Morinda citrifolia)
- Pukavai, (Pisonia grandis)
- Sageta vine, (Dioclea violacea)
- Talla talla gemoa fern, (Psilotum triquetrum)
- Tausoun, (Heliotropium foertherianum)
- Tonga, (Rhizophora mucronata), found around swamps
- Tulla tulla, (Triumfetta procumbens), whose prostrate stems trailed for several feet over the ground
- Valla valla, (Premna taitensis)
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.
Charles Hedley (1896) identified the uses of plants and trees from the native broadleaf forest as including:
- Food plants: Coconut; and Ferra, native fig (Ficus aspem).
- Fibre: Coconut; Ferra; Fala, Screw Pine, Pandanus ; Fau or Fo fafini, or woman's fibre tree (Hibiscus tiliaceus).
- Timber: Fau or Fo fafini; Pouka, (Hernandia peltata); Ngia or Ingia bush, (Pemphis acidula); Miro, (Thespesia populnea); Tonga, (Rhizophora mucronata).
- Dye: Valla valla, (Premna taitensis); Tonga, (Rhizophora mucronata); and Nonou, (Morinda citrifolia).
- Scent: Fetau, (Calophyllum inophyllum); Jiali, (Gardenia taitensis); and Boua (Guettarda speciosa); Valla valla, (Premna taitensis); and Crinum.
- Medicinal: Tulla tulla, (Triumfetta procumbens); Nonou, (Morinda citrifolia); Tausoun, (Heliotropium foertherianum); Valla valla, (Premna taitensis); Talla talla gemoa fern, (Psilotum triquetrum); Lou, (Cardamine sarmentosa); and Lakoumonong, (Wedelia strigulosa).
Thaman (1992) provides an literature review of the ethnobiology of the Pacific Islands.
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. 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. 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. 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.
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. Water pollution is also a chronic problem, with domestic wastewater identified as the primary pollution source. 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.
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. 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. Aid programs from the European Union and Australia also provided water tanks as part of the longer term solution for the storage of available fresh water.
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, Pulaka has been the main source for carbohydrates, it is similar to taro, but "with bigger leaves and larger, coarser roots".
In recent years the Tuvaluan community have raised concerns over increased salinity of the groundwater in pits that are used to cultivate pulaka. 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.
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.
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.
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