How the Galapagos Islands Work

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­Due to the islands' isolation, and depending on their wind and elevation, there are four main ecosystems across the archipelago:

Solid bare lava forms cliffs and coastlines.

There are more than 500 plant species found on the Galapagos, about one-third of which are endemic, meaning they're native to the islands and found nowhere else in the world. Exclusive species of cotton, guava, passion flower, pepper and tomatoes all grow here.

While explorers and sailors left behind some animal inhabitants, such as goats and pigs, much of the wildlife on the islands are endemic species, some exclusive to certain islands in the archipelago. Many are fearless from living without predators. The blue footed booby booby is one example: These birds have stopped nest building in their isolated habitat and lay eggs directly on the ground.

The Galapagos Islands are important because of these endemic species -- there are roughly 9,000 species living on the islands and in surrounding waters. Fourteen distinct subspecies of giant tortoise live on the islands, for example, as well as the only tropical-dwelling penguins. There are several reptile species including land and marine iguanas (marine iguanas are the only lizard known to swim in the ocean), lava lizards, geckos and snakes, 1,600 species of insects and 400 species of fish.

­Competing with the giant tortoises for most famous species on the islands are the 13 species of finches, known as Darwin's finches because they provided evidence for his theory of evolution by natural selection. These finches are an example of what's called adaptive radiation, the process of rapid speciation of a single species. Darwin's finches began as a single species of finch when they arrived on the islands, but through mutation and natural selection, they evolved into different species with different beak shapes -- giving each an advantage in the specific island habitats.

­The islands are also home to a small population of people. There are no known aboriginal tribes of the Galapagos. When people from the Ecuadorian mainland began moving to the Galapagos Islands, it was at a very slow rate. While the human population on the archipelago numbered as few as 1,500 in 1955, the modern-day population has swelled more than 19,000 residents as of 2006 [source: Galapagos Conservation Trust].

Tourism is big business on the islands, and the 160,000 tourists who visit the Galapagos to see its natural wonders produce $100 million in annual revenue for Ecuador [source: Telegraph and Inter-American Development Bank]. Coffee and cattle are the area's biggest exports. Work on the islands offers high salaries, up to 50 percent higher than those on the mainland. Although the Ecuadorian government tries to contain the islands' population growth, jobs are hard to resist in a country with a 40 percent unemployment rate [source: Galapagos Online].

The human impact -- both the growing rate of permanent residency and tourism -- poses a threat to the islands' ecosystems and availability of resources and services. Additionally, overfishing and the introduction of non-native species are causing environmental problems on the islands. An unsustainable rise in legal and illegal commercial fishing of sea cucumbers, shark fins and lobsters threatens marine ecosystems.

Non-native species introduced to the islands -- whether today when a plane touches down or hundreds of years ago when explorers landed -- have compete with endemic wildlife for food. Take goats, for instance. A handful of goats were brought to Santiago Island in the 1800s and were once estimated to number close to 100,000. The Galapagos goat population fed on native vegetation and competed with the giant tortoises for food, literally eating some species into extinction. That's why the Galapagos National Park Service pursued a dogged campaign to eradicate goats from several of the islands, including Pinta, Santiago and northern Isabela.

Since tourism began on the Galapagos in the 1960s, conservation efforts have been established on the islands. The Charles Darwin Foundation, a nonprofit organization focused on scientific research and conservation, is an active presence. Additionally, the Ecuadorian government established 90 percent of the archipelago as a wildlife preserve, the Galapagos National Park and Galapagos Marine Reserve.

­Under a new law, the Special Regime for the Galapagos, the government is attempting to limit migration, control development and protect native species and ecosystems. Yet despite conservation efforts, the World Heritage Committee added Galapagos to UNESCO's List of World Heritage Sites in Danger in 2007.