In this blog post, we will explore how the Galapagos Islands formed their unique ecosystem and had a significant impact on evolutionary theory.
The Galápagos Islands are located in the Pacific Ocean, approximately 1,000 kilometers off the coast of South America. The 19 islands and their surrounding marine protected areas are often referred to as a “living museum and showcase of evolution” due to their unique marine ecosystem. The convergence of three ocean currents makes the region a treasure trove of marine life. Ongoing seismic and volcanic activity continues to shape the islands, providing a vivid illustration of their geological formation. This unique environment, combined with the islands’ isolation from other landmasses, has contributed to the development of rare and distinctive animal species, such as land iguanas, Galápagos tortoises, and various finch species. These creatures played a pivotal role in inspiring Darwin’s theory of evolution during his 1835 visit to the islands.
The Galapagos Islands are located on the Galapagos Submarine Platform and consist of approximately 120 islands. The main islands include Isabela, Santa Cruz, Fernandina, Santiago, and San Cristobal. The region was formed by volcanic activity, with the tops of the volcanoes rising about 3,000 meters above the Pacific Ocean floor. Strong volcanic and seismic activity occurred in the western part of the archipelago. The main islands are composed of gently sloping shield volcanoes, characterized by collapsed craters and calderas.
The long coastline is somewhat eroded, but it features steep cliffs formed by faulting and marine erosion, as well as beaches composed of lava, coral, and shell fragments. Notable landmarks include crater lakes, fumaroles, lava caves, sulfur areas, and various volcanic rocks, and you can still see pumice, ash, and tuff erupting from the craters. The marine environment is also unique and highly diverse, which is related to the amount of light penetrating the water depending on water temperature and nutrient content.
The marine environment is diverse due to the warm water temperatures influenced by active upwellings (equatorial currents) and subtropical currents (Peru Current). The islands vary greatly in elevation, area, and orientation, and are physically separated from one another, resulting in the emergence of species endemic to specific islands. Coastal vegetation is primarily found along beaches, around saltwater lagoons, and in coastal lowlands with rocky sand. Mangrove swamps and lagoons are currently protected. As one moves inland from the coast, a dry zone extends, which is the predominant climate condition across most of the archipelago. A humid zone forms above the dry zone, and there are also transitional areas where the two climate zones meet.
The humid zone is a very wet area covered by thick fog called garua, which maintains sufficient moisture even during the dry season. The fog accumulates mainly at night and flows into the forest every day. The summit of the large island is covered with ferns, grasses, and sedges, and moisture is maintained thanks to temporary ponds.
The Galápagos Islands’ unique fauna includes invertebrates, reptiles, and birds, with a few native mammal species. Except for two species of sea turtles, all reptiles are endemic. The Galápagos tortoises have 11 subspecies, each specific to a different island, and are endangered. Other species include land iguanas, marine iguanas, three species of whip snakes, and various lizards and iguanas. The Galápagos Islands are home to over 57 bird species, 26 of which are endemic, and 31 are migratory. Endemic species include 13 species of Darwin’s finches, including the Floreana tree finch and the mangrove finch.
Other notable species in the Galápagos Islands include the Galápagos boobies, flightless Galápagos cormorants, Galápagos penguins, lava gulls, the Floreana mockingbird, the Galápagos boobies, the Galápagos sea eagle, the nocturnal swallow-tailed gull, the Galápagos woodpecker, the great-billed woodpecker, the Galápagos swallow, and the Galápagos dove. There are six native mammal species: the Galápagos fur seal, Galápagos sea lion, two species of rice rat, and two species of bat. The marine fauna includes sharks, rays, and various whale species. Sea turtles and olive ridley turtles are frequently observed along the coast, and sea turtles nest on the beaches.
