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The Natural History of the Galapagos Islands

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The Natural History of the Galapagos Islands

Sally Lightfoot Crab

Photo by Christopher Minster

The Natural History of the Galapagos Islands:

The Galápagos Islands are a wonder of nature. Located off the coast of Ecuador, these remote islands have been called “evolution’s laboratory” because their remoteness, isolation from one another and different ecological zones have allowed plant and animal species to adapt and evolve undisturbed. The Galapagos Islands have a long and interesting natural history.

The Birth of the Islands:

The Galapagos Islands were created by volcanic activity deep in the Earth's crust under the ocean. Like Hawaii, the Galapagos Islands were formed by what geologists call a "hot spot." Basically, a hot spot is a place in the Earth's core which is much hotter than usual. As the plates making up the Earth's crust move over the hot spot, it essentially burns a hole in them, creating volcanoes. These volcanoes rise up out of the sea, forming islands: the lava stone they produce shapes the topography of the islands.

The Galapagos Hot Spot:

In Galapagos, the Earth’s crust is moving from west to east over the hot spot. Therefore, the islands that are furthest to the east, such as San Cristóbal, are the oldest: they were formed many thousands of years ago. Because these older islands are no longer over the hot spot, they are no longer volcanically active. Meanwhile, islands in the western part of the archipelago, such as Isabela and Fernandina, were created only recently, geologically speaking. They are still over the hot spot and still very active volcanically. As the islands move away from the hot spot, they tend to wear down and become smaller.

Animals Arrive to Galapagos:

The islands are home to many species of birds and reptiles but relatively few native insects and mammals. The reason for this is simple: it’s not easy for most animals to get there. Birds, of course, can fly there. Other Galapagos animals were washed there on vegetation rafts. For example, an iguana might fall into a river, cling to a fallen branch and get swept out to sea, arriving to the islands after days or weeks. Surviving at sea for such a long time is easier for a reptile than it is for a mammal. For this reason, the large herbivores on the islands are reptiles like tortoises and iguanas, not mammals like goats and horses.

Animals Evolve:

Over the course of thousands of years, animals will change to fit their environment and adapt to any existing “vacancy” in a particular ecological zone. Take the famous Darwin’s finches of Galapagos. Long ago, a single finch found its way to Galapagos, where it laid eggs which would eventually hatch into a small finch colony. Over the years, fourteen different sub-species of finch have evolved there. Some of them hop on the ground and eat seeds, some stay in trees and eat insects. The finches changed to fit in where there was not already some other animal or bird eating the available food or using the available nesting sites.

Arrival of Humans:

The arrival of humans to the Galapagos Islands shattered the delicate ecological balance that had reigned there for ages. The islands were first discovered in 1535 but for a long time they were ignored. In the 1800's, the Ecuadorian government began settling the islands. When Charles Darwin made his famous visit to Galapagos in 1835, there was already a penal colony there. Humans were very destructive in Galapagos, mostly because of predation of Galapagos species and introduction of new species. During the nineteenth century, whaling ships and pirates took tortoises for food, wiping out the Floreana Island subspecies completely and pushing others to the brink of extinction.

Introduced Species:

The worst damage done by humans was the introduction of new species into Galapagos. Some animals, such as goats, were released intentionally onto the islands. Others, such as rats, were brought by man unknowingly. Dozens of animal species previously unknown in the islands were suddenly turned loose there with disastrous results. Cats and dogs eat birds, iguanas and baby tortoises. Goats can strip an area clean of vegetation, leaving no food for other animals. Plants brought for food, such as the blackberry, muscled out native species. Introduced species constitute one of the gravest dangers for the Galapagos ecosystems.

Other Human Problems:

Introducing animals was not the only damage humans have done to Galapagos. Boats, cars and homes cause pollution, further damaging the environment. Fishing is supposedly controlled in the islands, but many make their living by illicitly fishing for sharks, sea cucumbers and lobsters out of season or beyond catch limits: this illegal activity had a great negative impact on the marine ecosystem. Roads, boats and airplanes disturb mating grounds.

Solving Galapagos’ Natural Problems:

The park rangers and staff of the Charles Darwin Research Station have been working for years to reverse the effects of human impact on Galapagos, and they’ve been seeing results. Feral goats, once a major problem, have been eliminated from several islands. The numbers of wild cats, dogs and pigs are also declining. The National Park has taken on the ambitious goal of eradicating introduced rats from the islands. Although activities like tourism and fishing are still taking their toll on the islands, optimists feel that the islands are in better shape than they have been for years.

Source:

Jackson, Michael H. Galapagos: a Natural History. Calgary: the Universityof Calgary Press, 1993.

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