For centuries the Galápagos Islands have fascinated explorers and scientists and have served as a laboratory of evolution. Located just over 900km from mainland Ecuador, the equatorial, volcanic islands have only a few sources of freshwater, two climatic seasons, a wet and garua season, and the highest numbers of endemic species (species that cannot be found anywhere else in the world). The marine and terrestrial species of the islands inspired Charles Darwin’s theory of natural selection and is why the Galápagos Islands have been called “the birth place of modern biology”. Peter and Rosemary Grant (2014) have followed Darwin’s Finches on Daphne Major Island for 40 years documenting that natural selection continues at a rapid pace.
The islands are at the convergence zone of two major currents: the northward moving Humboldt (or Peruvian) Current and the eastward moving Equatorial Countercurrent (or Cromwell Current). Upwelling of deep, cool water derived from the Cromwell Current brings nutrients to the surface and drives the food chain that supports a wide range of species including the Galápagos penguin. Boersma started the first survey of the penguins in 1970’s and we hope you will join us in helping the conservation and understanding of the only penguin that lives on the equator.
The volcanic archipelago began to form approximately 5 million years ago. The present islands are about 3-4 million years old but there is evidence of a much more ancient origin of islands over the hot spot. Today 13 larger islands and 7 smaller islands make up the Galápagos. The islands were formed by a hotspot, or hole in Earth’s mantle through which lava from the Earth’s core rises to the surface. The hot spot lies on the western boundary of the islands, and the upward flow of lava continues to build and shape the Archipelago. As the Nazca plate moves East-southeast, away from the hotspot, the volcanoes cool and become inactive. With the exception of Isabela, which has 6 large volcanoes, each of the larger islands has one volcano, which vary in size and activity. Isabela is the largest of the Galápagos Islands and has the tallest of the volcanoes, Volcán Wolf, where a new species of pink land iguana was recently discovered. Isabela and Fernandina have the most active volcanoes, are the youngest, and have erupted several times since 2000. They are likely to continue to grow until the Nazca plate moves far enough away from the hotspot and new volcanoes are formed.
Arrival of Flora and Fauna
Arrival of Flora and Fauna
The Galápagos Islands were formed in the Pacific Ocean, and have never been attached to mainland South America. How then did the plants and animals make it to the Galápagos, and how do these isolated islands have such a high number of endemic species? Modes of dispersal play a key role in island colonization. While the earliest endemic plants likely arrived first via wind and water dispersal, later plants arrived on the feet and feathers, and in the digestive tract of birds. Active dispersal, such as flying and swimming, allowed animals such as birds and marine mammals to reach the islands, while “sweepstake” dispersal brought animals such as the giant tortoise and iguanas on debris washed off the mainland. The difficulty in crossing the ocean, finding the islands and surviving appears unlikely even in the best circumstances so presumably most species that arrived to the islands were not successful in colonization. Those that successfully established and reproduced faced new selective pressures that over time honed adaptations to their new home. Given time the result was speciation and a high number of endemic species. These endemic plants and animals of the Galápagos helped Darwin build his theory of natural selection, and was a driving force behind the acceptance of evolution.
New species are still coming to the islands faster today than in earlier times because they are aided, intentionally and unintentionally, by humans. Humans brought cats, dogs, donkeys, goats, cows, rats, and fire ants that kill the endemic species and compete for their resources. Programs to prevent introduction, mitigate the damage already done, and eradicate the invasive species try to control the damage but some introduced species still continue to pose a large threat to many of the already endangered endemic species of the Galápagos Islands.
Arrival of People
While many are familiar with Darwin’s famous Voyage of the Beagle in 1835, the first written account of discovery of the Galápagos, made by Fray Tomás de Berlanga, Bishop of Panama, came 300 years before Darwin in 1535. Throughout the early 1800s intense exploration and exploitation devastated fauna. It is estimated that tens of thousands of fur seals were harvested and over 100,000 giant tortoises were removed. The first colonization of humans occurred in 1832. The human population stayed moderate until the 1970s, but with a sharp increase in tourism the permanent resident population increased rapidly. Between 1995 and 2005 the population increased by 60% (www.galapagos.org). The growing human population creates many challenges for the Galápagos National Park as they try and manage the increasing human demand for resources while protecting the land, flora, and fauna of the islands.
Click here for a timeline of exploration, research, and development in the Galápagos.
In the early 1930s people began to recognize the importance of conservation in the islands and requested that the government of Ecuador declare some of the species protected. In 1959 Ecuador formed the Galápagos National Park, and in 1998, after an expansion of its boundaries, the Galápagos Marine Reserve was formed. In 1978 the islands were listed as UNESCO World Heritage Site by the United Nations, but in 2007 were placed on the list of “World Heritage Sites in Danger” due to uncontrolled immigration and other conservation challenges. Internationally humans are also having a negative impact on the climate of the Galápagos. Increased use of fossil fuels has caused global warming associated with the increased severity and frequency of El Niños. During these events the currents slow, which decreases upwelling and food becomes scarce. Although we cannot manage climate and oceanic conditions in the short-term, the Galápagos National Park, conservation groups, including the Galápagos Conservancy, and researchers, such as the Center for Penguins as Ocean Sentinels, the iGalápagos project, and the Charles Darwin Foundation are trying hard to find ways to balance human resource use and protection of the diverse, endemic species of these islands.
Grant, P.R. and Grant, B.R. 2014. 40 years of Evolution. Princeton University Press, 400p.
Thornton, Ian. Darwin’s Islands: A Natural History of the Galápagos. N.p.: American Museum of Natural History, 1971. Print.