| A
visit to Galapagos is all about seeing and experiencing nature at
close quarters; not only wildlife
including birds, but also
geology and the evolutionary forces working almost visibly behind
the scenes. Given its isolation 1,000kms off the South American
continent, the development of the islands has been shaped by
geology, climate and currents in such an evident fashion that Galapagos
is considered an evolutionary laboratory.
The
Galapagos, volcanic in origin and formed about 3-5 million years
ago, is one of the world's areas of greatest volcanic activity.
More than 50 eruptions have occurred in the last 200 years, with
activity concentrated in the western islands of Fernandina and Isabela
where fumaroles can be seen rising in the air. Geologically the
Galapagos islands are very young and in active development.
The
climate is a key factor behind the islands' unique development.
In particular, given the islands' distance from the mainland, weather
is determined by ocean currents, in turn affected by winds.
Galapagos is the meeting point of several currents, mainly the cold
Humboldt Current from the south and the much warmer Panama Current
from the north. From July to December the trade winds blow the Humboldt
Current towards the Galapagos, so the result is a cool climate,
an inversion layer which frequently produces a fine mist or garua,
and dryness. This is the dry season. From January the trade winds
disappear, and the Panama Current then dominates to produce warmer
waters, and more normal tropical weather.
The
islands' unique wildlife has been shaped by the climate
and the islands' isolation. Once there, wildlife has evolved in
response to the climate without influence from the mainland, and
without being able to influence the mainland. This accounts for
the exceptionally high number of species unique to the islands -
ie endemism. One third of the 600 plant species, a fifth
of the inshore fish of 400 fish species, and more than three
quarters of the land-based animals (which include 58 resident
bird species, 22 reptile species, and 6 mammals) are endemic. And
many species are only found on one or a few of the Galapagos islands,
as described by Darwin:-
"By
far the most remarkable feature in the natural history of this
archipelago.... is that the different islands to a considerable
extent are inhabited by a different set of beings. I never dreamed
that islands, about fifty or sixty miles apart, and most of them
in sight of each other, formed of precisely the same rocks, placed
under a quite similar climate, rising to a nearly equal height,
would have been differently tenanted...."
Charles Darwin 1845
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