The flora and fauna of Bermuda forms part of a unique ecosystem thanks to Bermuda's isolation from the mainland of North America. There are a wide range of endemic species and the islands form a distinct ecoregion, the Bermuda subtropical conifer forests.
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Located in the Atlantic Ocean 900 km off the American coast Bermuda is a crescent-shaped chain of 181 islands and islets that were once the rim of a volcano. The islands are slightly hilly rather than having steep cliffs with the highest point being only 79m and the coast has many bays and inlets, with sandy beaches especially on the south coasts. Bermuda has a wet tropical climate, warmed by the Gulf Stream current. Twenty of the islands are inhabited and Bermuda is one of the most densely populated countries in the world.
Being so remote they have only wildlife which were able to fly to the island or were carried by winds and currents. Therefore there are no native mammals other than bats, and only one reptile, but large numbers of birds, plants, and insects. Once on the island, organisms had to adapt to local conditions such as the humid climate, lack of fresh water, frequent storms and salt spray. The islands shrank as water levels rose at the end of the Pleistocene epoch and fewer species were able to survive in the reduced land-area. Nearly 8,000 different species of flora and fauna are known from the islands of Bermuda and the number is likely to be considerably higher if all micro-organisms, cave-dwellers and deep-sea species were counted.[1]
Today the variety of species on Bermuda has been greatly increased by introductions, both deliberate and accidental. Many of these introduced species now pose a threat to the native flora and fauna.
Over 1000 species of vascular plant are found on the islands, the majority of which are introduced. Of the 165 native species, 15 are endemic.
At the time of the first human settlement, by shipwrecked English sailors in 1593, Bermuda was dominated by forests of Bermuda Cedar[2] with mangrove swamps on the coast. Clearance of planting began immediately and by the 1830s, the shipbuilding industry had denuded the landscape, but the forest was able to recover. In the 1940s the cedar forests were devastated by introduced scale insects which killed roughly 8 million trees. Replanting using resistant trees has taken place since then but the area covered by cedar is still only 10% of what it formerly was. Another important component of the original forest was Bermuda Palmetto, a small palm tree which now only grows in a few small patches, notably at Paget Marsh. Other trees and shrubs include Bermuda Olivewood and Bermuda Snowberry.
There are remnant patches of mangrove swamp around the coast and at some inland sites including Hungry Bay Mangrove Swamp and Mangrove Lake, where Black Mangrove and Red Mangrove are the northernmost mangroves in the Atlantic. The inland swamps are particularly interesting as mangroves thrive in salty water, in this case provided through underground channels rather than the usual tidal wash of coastal mangrove swamps. There are also areas of peat marsh including Devonshire Marsh, Pembroke Marsh, and Paget Marsh.
Bermuda has four endemic ferns[3]: Bermuda Maidenhair Fern, Bermuda Shield Fern (Goniopteris bermudiana), Bermuda Cave Fern (Ctenitis sloanei) and Governor Laffan's Fern (Diplazium laffanianum). The latter is extinct in the wild but is grown at Bermuda Botanical Gardens. The endemic flora of the island also includes two mosses, ten lichens and forty fungi.
Among the many introduced species are the Beach Sheoak (Casuarina equisetifolia) and Surinam Cherry (Eugenia uniflora)
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Bermuda has no native amphibians. However, one species of toad, Rhinella marina, and two species of frog, Eleutherodactylus johnstonei, and Eleutherodactylus gossei were introduced by humans and subsequently became naturalized. R. marina and E. johnstonei are common, but E. gossei is thought to have been recently extirpated.
Four species of lizard and two species of terrapin comprise Bermuda's non-marine reptilian fauna. Of the lizards, the endemic Bermuda Skink, Eumeces longirostris, is the only non-introduced species. Once very common, the Bermuda Skink is now critically endangered. The Jamaican Anole, Anolis grahami, was deliberately introduced in 1905 from Jamaica and is now by far the most common lizard in Bermuda. The Antiguan Anole, Anolis leachii, was accidentally introduced from Barbados about 1940 and is now common. The Barbados Anole, Anolis roquet, was accidentally introduced about 1940 and is rarely seen. The Diamond-Back Terrapin, Malaclemys terrapin, is native to Bermuda. The Red-Eared Slider, Trachemys scripta elegans, was introduced as a pet, but has subsequently become invasive.[4]
All mammals in Bermuda are human introductions, except for four species of migratory North American bats of the genus Lasiurus: the Hoary Bat, Eastern Red Bat, Seminole Bat and Silver-haired Bat. The House Mouse, Brown Rat and Black Rat were accidentally introduced very soon after the settlement of Bermuda and feral cats are common. Early accounts also refer to wild hogs.
Over 360 species of bird have been recorded on Bermuda. The majority of these are migrants or vagrants from North America or elsewhere. Only 24 species breed; 13 of these are thought to be native.
There is one endemic species, the Bermuda Petrel or Cahow (Pterodroma cahow), which was thought to be extinct until a breeding pair was spotted in the 1950s and a recovery program began. There is also an endemic subspecies, the Bermuda White-eyed Vireo or Chick-of-the-village (Vireo griseus bermudianus). The national bird of Bermuda is the White-tailed Tropicbird or Longtail which is a summer migrant to Bermuda, its most northerly breeding site in the world. Other native birds include the Eastern Bluebird, Grey Catbird and perhaps the Common Ground-Dove. The Common Moorhen is the commonest native waterbird with very small numbers of American Coot and Pied-billed Grebe breeding. Small numbers of Common Tern nest around the coast. The Barn Owl and Mourning Dove colonized the island during the 20th century and the Green Heron has recently begun to breed.
Of the introduced birds, the European Starling, House Sparrow, Great Kiskadee, Rock Dove and American Crow are all very numerous and considered to be pests. Other introduced species include the Mallard, Northern Cardinal, European Goldfinch and small numbers of Orange-cheeked and Common Waxbills. The Yellow-crowned Night Heron was introduced in the 1970s to replace the extinct native heron.
Fossil remains of a variety of species have been found on the island including a crane, an owl and the Short-tailed Albatross. Some of these became extinct as the islands' land-mass shrunk while others were exterminated by early settlers. The Bermuda Petrel was thought to be extinct until its rediscovery in 1951.
Among the many non-breeding migrants are a variety of shorebirds, herons and ducks. In spring many shearwaters can be seen of the South Shore. Over 30 species of New World warbler are seen each year with the Yellow-rumped Warbler being the most abundant. The arrival of many species is dependent on weather conditions with low-pressure systems moving across from North America bringing many birds. Among the rare visitors to have occurred are the Siberian Flycatcher from Asia and the Fork-tailed Flycatcher and Tropical Kingbird from South America.
More than 1100 kinds of insect and spider are found on Bermuda including 41 endemic insects and a possibly endemic spider. 18 species of butterfly have been seen, about six of these breed including the large Monarch and the very common Bermuda Buckeye (Junonia coenia bergi). More than 200 moths have been recorded, one of the most conspicuous is Pseudosphinx tetrio which can reach 9 cm (3.5 in) in length.
Bermuda has lost a number of its endemic invertebrates including the Bermuda Cicada (Tibicen bermudiana), which became extinct when the cedar forests disappeared. Some species feared extinct have been rediscovered including a Bermuda land snail (Poecilozonties circumfirmatus) and the Bermuda Ant (Odontomachus insularis).
Bermuda lies on the western edge of the Sargasso Sea, an area with high salinity and temperature and few currents. Large quantities of seaweed of the genus Sargassum are present and there are high concentrations of plankton but the area is less attractive to commercial fish species and seabirds.
Greater diversity is present in the coral reefs which surround the island.
A variety of whales, dolphins and porpoises have been recorded in the waters around Bermuda. The most common of these is the Humpback Whale which passes the islands in April and May during its northward migration.
Bermuda was the first place in the Americas to pass conservation laws, protecting the Bermuda Petrel in 1616 and the Bermuda Cedar in 1622, and continue to have a well-organised network of protected areas including Spittal Pond, marshes in Paget and Devonshire and Pembroke Parishes, Warwick Pond and the hills above Castle Harbour. However only small areas of natural forest remain today as most has been cleared since colonisation began in the 17th century, while the Bermuda Petrel and Bermuda skink are highly endangered and Bermuda Cedar, Bermuda palmetto and Bermuda olivewood are all listed as threatened species, and some wildlife including a spike rush have disappeared. Introduced plants and animals have also had an impact on the wildlife of the islands, and the thriving tourist industry brings its own challenges to wildlife and habitat protection.
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