Maldives-Lakshadweep-Chagos Archipelago tropical moist forests
The Maldives-Lakshadweep-Chagos Archipelago is an unusual sight viewed from the air. In this region of the Indian Ocean, many thin ring-shaped atolls stand out against blue ocean with their extensive reef system visibly spreading offshore. While it is this reef system that receives the majority of attention from the conservation community, the terrestrial portion of this system of thousands of islands serves as important habitat for several species. Many of the islands are major seabird rookeries and are also important turtle nesting areas. Two fruit bats and a few butterflies are endemic to the archipelago. Once covered in tropical rain forest, almost all native vegetation has been cleared.
Location and General Description
Maldives, Lakshadweep and Chagos are three island groups in the Indian Ocean that together form a vast submarine mountain range, the Chagos-Laccadive Plateau. This volcanic range lies just east of the Mid-Indian Ridge and west of the Mid-Indian Basin. The Vema Fracture Zone lies underwater to the southeast of Chagos. The chain of islands are aligned north to south between 72°-74° E. Altogether, the Maldives-Lakshadweep-Chagos Archipelago comprises the most extensive coral reef and atoll community in the Indian Ocean as well as the largest atoll system in the world.
Lakshadweep is the closest group to the mainland, lying a little more than 300 kilometers (km) from the Kerala coast of India, at 8°-14° N. Thirty-six tiny islands make up Lakshadweep’s land area of 32 km2. A few of these islands are little more than sandbanks, and only ten are inhabited. These islands form the Lakshadweep Union Territory of India. Maldives, to the south of Lakshadweep, lies on the equator at 7° N and is the largest group of islands. There are approximately 1,190 Maldivian islands; the number fluctuates as islands come and go with climate and sea level change. All together, Maldives covers an area of 298 km2. Maldives gained independence from Britain in 1965. Two-hundred of the islands are inhabited, with a population estimated at 301,475 in 2000. Additionally, about 80 islands house tourist resorts. Chagos is the most remote group of islands, located at 5°-8° S. Roughly 500 km south of the Maldives, the Chagos Islands are uninhabited, aside from Diego Garcia, which is used as a US military base. More than 50 islands in the group cover a total area of 60 km2. Chagos is part of British Indian Ocean Territory, though the Seychelles disputes this, also claiming Diego Garcia Island.
The Maldives-Lakshadweep-Chagos Archipelago is composed entirely of low atolls, associated coralline structures, and sandy islands, which have grown upon the crest of the submarine Chagos-Laccadive Ridge. Many islands compose each ring-shaped atoll, and the highest islands reach only 5 m above sea level. Therefore, smaller islands are often washed away or submerged with a small rise in sea level. The Maldivian atolls are a classic example of its kind, containing extensive and largely intact reefs, and comprising perhaps one of the world's most complex reef systems. The Chagos Archipelago has the largest expanse of undisturbed reefs in the Indian Ocean, as well as some of the most diverse. In addition to five atolls, including the Great Chagos Bank, the world's largest atoll in terms of area, there are two areas of raised reef and several large submerged reefs. There are no ancient rocks in the archipelago’s current geological structure. Exposed coral rock erodes into white coral sand that is shallow, alkaline, nutrient-poor, and that has low water retaining capacity. Generally, freshwater occurs about 1-3 m beneath the surface, floating above salt water. Though some of the islands have small lakes, fresh water can be a scarce resource.
The climate of this archipelago is monsoon tropical, with a dry season associated with the winter northeast monsoon lasting December to March and the rainy season of the southwest monsoon from April to October. Annual rainfall varies from lows around 1,600 millimeters (mm) in the drier Lakshadweep Islands, to highs over 3,800 mm in parts of the southern Maldives. Temperatures vary little this close to the equator, generally ranging between 24°C and 30°C. Humidity is usually high, though constant breezes are present to stir the air. Monsoons can be severe, occasionally causing tidal waves capable of uprooting large trees, flooding arable land with seawater, and destroying houses and piers.
The natural vegetation of the Maldives-Lakshadweep-Chagos Islands with substantial enough soil is tropical rain forest. Islands with poorer soil support a shrub cover of hardy salt and drought resistant bushes and Cyperaceae species. However, very little of this native ecosystem remains undisturbed. Littoral trees were once prominent; now scattered remnants of the original vegetation are found on some islands. For example, stands of the shrub Scaevola and the treelet Argusia can be found at Lakshadweep. Chagos may be the least disturbed group, supporting broadleaved woodland of Ficus, Morinda and Terminalia (especially on smaller islands), Casuarina woodland, mixed coconut woodland, Scaevola scrub, and marsh communities. Many species have been introduced and are naturalized; coconut is cultivated extensively along with other fruit trees where viable.
Rao and Shastry classified the vegetation of the Lakshadweep Islands as Strand Coral. This includes an open pioneer zone, woodland zone, and coastal zone, each with a dominant tree or plant. Again, little of the original vegetation is left, as much of the land is cultivated for coconuts. One tract of the native mangrove Bruguiera parviflora remains on Mincoy Island, covering only 2,500 meters squared (m2). Neither flora nor fauna of these islands has any significant endemism. Rather, the vegetation is typical of Indo-Pacific coral island flora. The plants present are primarily of pantropical or cosmopolitan distribution, the main components being Sri Lankan (44%), African (28%), Malaysian (25%), and the remainder from distinct coral habitats.
Terrestrial animals are limited on these islands, and most species are not unique but are widely distributed throughout other oceanic Indo-Pacific atolls. The only native mammals on the islands are two species of fruit bat, Indian flying fox (Pteropus giganteus ariel) and a subspecies of variable flying fox (Pteropus hypomelanus maris). Both are of conservation concern; the latter is quite rare with only a few recordings. Important marine mammals are short-beaked saddleback dolphin (Delphinus delphis) and a subspecies of Cuvier's beaked whale (Ziphius cavirostris indicus).
The islands are particularly important for resident and breeding birds. Birds of special concern include an endemic subspecies, the Maldivian pond heron (Ardeola grayii phillipsi), white tern (Gygis alba monte), lesser frigate (Fregata ariel iredalei), black-naped tern (Sterna sumatrana), brown-winged tern (S. anaethetus), and large-crested tern (S. bergi). Thirteen to fourteen seabirds are known to nest on Maldives, and large rookeries are also present on Chagos and Lakshadweep. Important populations of red-footed booby (Sula sula) inhabit Chagos.
The Maldives and Chagos islands are important nesting sites for the endangered green turtle (Chelonia mydas). Other sea turtles likely using the islands are the Olive Ridley turtle (Lepidochelys olivacea), leatherback turtle (Dermochelys coriancea), loggerhead turtle (Caretta caretta gigas), and hawksbill turtle (Eretmochelys ambricata). Reptiles and amphibians recorded from the islands include 2 geckoes (Hemidactylus spp.), 2 agamid lizards including the common garden lizard or blood sucker (Calotes versicolar), the snake skink (Riopa albopunktata), common wolf snake (Lycodon aulicus), another snake, Typhlos braminus, a short-headed frog, Rana breviceps, and a larger toad, Bufo melanostictus. Many invertebrates are recorded from the islands, including two endemic butterflies, Hypolimnas bolina euphorioides and Junonia villida chagoensis.
Due to their isolation, fragile ecosystems, and great vulnerability to environmental deterioration, the biodiversity of islands worldwide is critically threatened. This is true even more so in the case of islands such as these, which are very small and far offshore. It is believed that humans have been living on the islands of this archipelago as early as the 5th century B.C. in the case of Maldives. Their presence has dramatically changed the nature of the islands in several ways. Most native vegetation was cleared by the early 19th century and replaced by coconut plantations and other crops. These now include banana, coconut (Cocos nucifera), sweet potatoes, mango (Mangifera indica), chico (Pouteria sapota), yams, taro, millet, watermelon, and citrus and pineapples on more fertile islands. Introductions of domestic animals such as cat, chicken, goat, rabbit, house mouse, black rat, Indian house shrew and donkey has had a severe effect on native fauna. Sand mining was once common, and coral mining has caused significant damage to the reefs. The collection of birds and eggs has long been a source of food for islanders, but the activity has grown past a sustainable point in many areas. For example, local fishermen have always collected eggs from Tern Sanctuary on the island of Pitti, Lakshadweep. Though it is now illegal, the activity continues and increased demand has lead to unsustainable quatities being removed. The two endemic fruit bats on the islands (Pteropus giganteus ariel and Pteropus hypomelanus maris) are thought to cause damage to crops such as almond, mango and guava, and thus are severely threatened by targetted culling.
Other threats include pollution from factories, increased shipping traffic with the risk of oil spills and dumping, depletion of freshwater aquifers, inadequate waste disposal, and the overuse of water pumps and fertilizers for agriculture. The only protected areas on these island groups are several islands of Chagos, which were designated as strict nature reserves after the forced evacuation of inhabitants in the early 1970’s when the military base was established on Diego Garcia. Tourist activities are not allowed on the protected islands.
Types and Severity of Threats
An immediate threat to the Maldives-Lakshadweep-Chagos Islands may come from the relatively rapid establishment and growth of the tourist industry. Natural vegetation is often cleared to make the islands "more attractive". On several islands the organic litter is burned and thus lost to the island ecosystem. The introduction of mechanized fishing is a primary concern in the health of the vast reefs surrounding the islands, and may have some level of effect on the islands as well. A general change in the lifestyles of the islanders towards more modern practices has brought with it serious conservation concerns. For example, trash from plastic and aluminum packaging has become an overwhelming problem for some of these tiny islands, which cannot afford room to dispose of it and have difficulty removing any trash from the island.
The foremost future threat to the island chain is potential global climate change. The low level of these islands makes them very sensitive to sea level rise. 1998 was the warmest year on record and the 1990s were the warmest decade since temperature recording began about 150 years ago. Additionally, 1998 saw the strongest El Nino ever recorded. The consequences of this were felt strongly in the tropical Indian Ocean, often with temperatures of 3-5°C above normal. Severe coral bleaching occurred during 1998, with mortality rates as high as 90% in some parts of the Maldives. Rising sea levels could lead to potentially acute erosion, particularly in the Maldives. Some islands in this region of the Indian Ocean could conceivably disappear into the sea as a result of global warming.
Justification of Ecoregion Delineation
The Maldives-Lakshadweep-Chagos Archipelago is comprised of three offshore island groups in the Indian Ocean that together form a vast submarine mountain range, the Chagos-Laccadive Plateau. Altogether, these islands form the most extensive coral reef and atoll community in the Indian Ocean as well as the largest atoll system in the world. Their isolation and coralline structure contributes to a habitat unique from that of the mainland or other nearby islands.
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