Situées dans l’océan Pacifique, à environ 1000 km du continent sud-américain, ces dix-neuf îles et la réserve marine qui les entoure constituent un musée et un laboratoire vivants de l’évolution uniques au monde. Au confluent de trois courants océaniques, les Galápagos sont un creuset d’espèces marines. L’activité sismique et le volcanisme toujours en activité illustrent les processus qui ont formé ces îles. Ces processus, ainsi que l’isolement extrême de ces îles, ont entraîné le développement d’une faune originale - notamment l’iguane terrestre, la tortue géante et de nombreuses espèces de pinsons qui inspira à Charles Darwin sa théorie de l’évolution par la sélection naturelle à la suite de sa visite en 1835.
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Situated in the Pacific some 1,000 km from the South American continent, these islands and the surrounding marine reserve have been called a unique 'living museum and showcase of evolution'. Located at the confluence of three ocean currents, the Galápagos are a 'melting pot' of marine species. Ongoing seismic and volcanic activity reflect the processes that formed the islands. These processes, together with the extreme isolation of the islands, led to the development of unusual animal life such as the land iguana, the giant tortoise and the many species of finch that inspired Charles Darwin's theory of evolution following his visit in 1835.
The site is situated on the Galápagos Submarine Platform, and consists of about 120 islands. The larger islands are Isabela, Santa Cruz, Fernandina, Santiago and San Cristobal. The islands were formed by volcanic processes and most represent the summit of a volcano, some of which rise over 3,000 m from the Pacific floor. The western part of the archipelago experiences intense volcanic and seismic activity. The larger islands typically comprise one or more gently sloping shield volcano, culminating in collapsed craters or calderas. Long stretches of shoreline are only slightly eroded, but in many places faulting and marine erosion have produced steep cliffs and lava, coral or shell sand beaches. Other noteworthy landscape features include crater lakes, fumaroles, lava tubes, sulphur fields and a great variety of lava and other ejects such as pumice, ash and tuff.
The marine environments are highly varied and are associated with water temperature regimes reflecting differences in nutrient and light levels. These range from warm temperate conditions brought on by vigorous upwelling (Equatorial Undercurrent) and a moderately cool, warm temperate-subtropical influence (Peru Flow).
There is considerable variation in altitude, area and orientation between the islands which when combined with their physical separation, has contributed towards the species diversity and endemism on particular islands. Coastal vegetation occurs along beaches, salt-water lagoons and low, broken, boulder-strewn shores. Protected coves and lagoons are dominated by mangrove swamps. The arid zone is found immediately inland from the coastal zone, and is the most widespread formation in the islands. The humid zone emerges above the arid zone through a transition belt in which elements of the two are combined. It is a very damp zone maintained in the dry season by thick, garua fogs which accumulate through most of the night and last well into each day. A fern-grass-sedge zone covers the summit areas of the larger islands where moisture is retained in temporary pools.
The endemic fauna includes invertebrate, reptile and bird species. There are a few indigenous mammals. All the reptiles, except for two marine tortoises, are endemic. These include the Galápagos giant tortoise, with 11 subspecies on different islands, all of which are endangered, terrestrial iguanas, marine iguana, three racer species, numerous lizards of the genus and geckos. The native avifauna includes 57 residents, of which 26 (46%) are endemic and 31 are regular migrants. Endemic taxa include 13 species of Darwin's finches, including Floreana tree finch and mangrove finch. Other noteworthy species include dark-rumped petrel, Galápagos flightless cormorant, Galápagos penguin, lava gull, Floreana mockingbird, Galápagos hawk, lava heron, nocturnal swallow-tailed gull, Galápagos rail, thick-billed flycatcher, Galápagos martin and Galápagos dove. The native mammalian fauna includes six species: Galápagos fur seal, Galápagos sea lion, two species of rice rat, bat and hoary bat. Marine fauna includes several species of sharks, rays and Cetaceans. Green turtle and hawksbill turtle are common in surrounding waters, with the former nesting on sandy beaches. Source : UNESCO/CLT/WHC