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The Central American isthmus only started rising above the ocean
3 million years ago, creating an evolutionary link between the
North and South American continents. This emerging land bridge
triggered a surge of animals and plants in both directions, and
the resulting cross-fertilisation has created one of the world's
most exciting and fascinating environments. Many species which
died out elsewhere still remain in Costa Rica.
Costa Rica's biodiversity attracts nature lovers from around the
world. A study by the World Resources Institute in 1995 put Costa
Rica at the top in terms of the most fauna per unit area: 615
per 10,000 sq kms (which compares with 104 for USA). In its 12
distinct ecological zones the country has around 5% of the world's
species, for a land size of 0.3% of the world. The whole of Africa
has less butterfly species than Costa Rica, and USA less than
half the bird species.
Some rough figures for species in Costa Rica:
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1,400
trees 10,000 plants
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1,400
orchids
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30
heliconias
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800
ferns (more than North America and Mexico)
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850
birds (visit Zoo Ave to see some)
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50
hummingbirds
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200
mammals
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160
amphibians
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200
reptiles (of which half snakes) to see more Serpentarium,
turtles
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1,000
butterflies (10% of world) to see more
Butterfly Farm
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