Geology The geology of the Galapagos islands rose from deep within the Earth. The islands were created by hot rock columns, also known as mantle plumes. These mantle plumes eventually create a group of volcanic islands, which is the foundation of the Galapagos Islands. It is believed that the Galapagos Archipelago, the location best known for its endemic life, was created by a deep-rooted mantle plume. Due to these plumes having hotter temperatures and lower densities than the surrounding rock, they begin to rise. As they rise and begin to near the surface, decompression causes the plumes to melt causing magma.
The cool and rigid layer of Earth, the lithosphere, prevents the newly formed magma from further rising. Once prevented, the magma is trapped in magma chambers, similar to a large pool. Although the magma is trapped, occasionally the magma will force its way through the lithosphere and causes a volcanic eruption. Forced eruptions that continue to take place over hundreds of thousands of years, a volcano will begin to form. The upward movement of the mantle plumes and volcanic eruptions caused a magnetic thickening of the Earth’s crust. The combination of these phases eventually created the Galapagos platform.
Plate tectonics have also played a role in the development of the Galapagos Islands. The lithosphere contains on average two dozen plates that move in sync with one another. As the plates move, the Earth experiences convection which causes heat loss. When the plates move across a mantle plume, chains of volcanoes are produced. The direction of plate movement will also determine the age of the volcanoes. When the movement of the plates carries the volcano away from the mantle plumes and magma source, the volcano will become extinct. The extinct volcano and the lithosphere cools and contracts, causing the volcano to sink beneath the sea, consequently creating islands and eventually seamounts, depending on the islands age.
Species Arrival Through oceanographic expedition, it is believed that the Galapagos Islands are at least 8 million years old. It is also believed that the mantle plume that created the islands are at least 90 million years old. Determining the exact age of the Galapagos Islands helps to understand the origin and evolution of the animals and plant life that inhabit them. The location of the islands, located along the equator, create sunny and hot conditions combined with cool ocean currents. This combination causes tropical and temperate conditions, providing the best environment for the unique and complex diversity found on the islands. As stated previously, islands and seamounts are created after volcanoes sink beneath the sea. Roughly 10 million years ago, the very tops of these submerged volcanoes remained uncovered by the water, completely vacant of any life forms. It is believed that animals and plants inhabited the vacant land form in two ways: by sea and by air.
The life that inhabited the islands by sea is believed to have swam or floated through the water and stumbled upon the uninhabited land. Marine mammals, such as sea lions, are very good swimmers. This allowing them to swim and be pushed through the ocean currents. Mammals who are not good swimmers, such as rats and reptiles, are believed to have been brought to the uninhabited islands by transportation on bundles of vegetation similar to a raft. Similar to non-swimming animals, plants seeds were also transported but by the ocean currents. Certain plant seeds, such as mangroves, have a tolerance to salt which allows for the survival of the plant species and the ability to inhabit the vacant land. The life that inhabited the islands by air is very similar to sea transport. Seeds, insects and flying birds were carried are believed to have been carried away by the winds power and brought to the uninhabited land. It is likely that the insects and birds needed to rest, discovered the land and eventually inhabited it.
Challenges of Eradication and Causes of Species Decline Non-native and invasive species have been brought to the islands through the increase of human population. Ecotourism and the exportation and importation of goods have allowed for invasive species to be brought over to the islands. The species are brought over by attaching themselves to the clothes and shoes of humans and by occupying the crates carrying the goods. All in all, the increase of humans has led to a decline in the endemic and native species that first populated the islands. Two species that have led to the decline in endemic and native species include feral pigs and donkeys which have threatened native flora and fauna and have changed the ecosystems dynamics.
The feral pig’s preyed on animal eggs and hatch-lings. To eradicate feral pigs from the islands, hunting and poisoning methods were used. Hunting methods that use traps and snares were ineffective, pigs would escape the traps. Hunting methods that used hunting dogs were primarily effective but occasionally ineffective due to the lack of dog training. The dogs had no issues capturing the pigs but would let the pigs go to attack goats and other animals. The use of poisons was very effective in the beginning but the pigs started to sniff out the poisons and avoided the poisoned food traps. Hunting and poisoning were very effective methods used for eradicating the pigs. After 150 years, the Santiago Islands and 25 other worldwide islands are now completely free of feral pigs.
The feral donkeys have caused destruction to the habitat due to overgrazing and have caused species to become endangered or extinct. Donkeys, for example, have trampled tortoise and iguana nests, decreasing their populations. Unfortunately, the most successful techniques of eradication have not been recorded, making it difficult to determine the most effective techniques for removal. Similar to pig eradication, hunting was one of the main methods of feral donkey removal. After 120 years, feral donkeys are finally removed from Santiago Islands, Alcedo Volcano and five other islands.
Galapagos Biodiversity The decline of endemic and native species aside, the Galapagos Islands have the largest amounts of biodiversity. Reptiles make up 97%, land birds make up 80%, endemic plants make up 30% and marine mammals, such as the Galapagos tortoise, marine iguana and Galapagos penguin, make up 20% of the biodiversity. The Galapagos Islands are also made up of three very different and major vegetation zones: coastal, arid and humid zones. The coastal zones are found near the shore and contain species with salt tolerance. Mangrove trees can be found among the coastal zones. The arid zones contain species that are adapted to drought, such as cacti. The humid zone is found above dry zones, they contain very lush and green moss, liverworts and epiphytes.
The Galapagos tortoise first inhabited the coast, floating on vegetation rafts. An animal that once flourished now suffers from extinction. These giant tortoises can be found in arid zones, where they adapted to drought. They are known to be able to survive without food and water for up to a year. Traveling voyagers discovered the tortoise’s adaptation and began storing them on their ships, using them for meat. The oil produced by this animal was also used for creating oil powered lamps in Quito. Predation on their eggs and hatch-lings and competition for food with humans and other animal species have also contributed to this species loss. After being exploited for two centuries, there has been a loss of 100, 000 to 200,000 Galapagos tortoises.
Marine iguanas and sea birds have also experienced species loss in the Galapagos Islands. Adult and young iguanas are preyed on and killed by dogs and cats. Like the tortoises, iguanas must compete for food with other species such as goats. A lack of food has caused iguanas to shrink in size, causing inconsistencies in their reproduction rates. Land and sea birds are threatened by the increase of human population and natural disasters. For example, El Niños caused a decline of birds by decreasing their food supply and affecting their nesting habitats.
Mangrove Forests Mangrove forests contain three species of trees: White, Black and Red mangroves. Of the three species, red mangroves dominates the outside edge of and creates the forests canopy. The tree tops and roots of the trees provide habitat and shelter for aquatic and terrestrial species.
The leaves of mangroves that fall into the below water provide a sequence of food chains for the aquatic organisms. Microorganisms, break down the leaves. Filter feeders, such as oysters and sponges, consume the detritus. The organic material that has been dissolved is then consumed by larger organisms, such as fish and shrimp. The Mangrove snapper, for example, relies on the roots for food as well as shelter. The lack of predators and over fishing has allowed the population of mangrove snapper to flourish.
Mangroves also provide many services to the ecosystem, including water filtration, carbon sequestration, and storm buffering. Mangroves filter the waters by slowing down the flow of water and trapping the sediment within. The sediment not contained is further filtered by filter feeders. They have also been known for collecting trash floating in the water. Studies have shown that mangroves possess the ability to effectively trap carbon and reduce greenhouse emissions. Unfortunately, mangroves are threatened by the increase sea level rise caused by climate change. Due to their strong, deep roots, mangroves are perfect storm buffers. They have the ability to withstand strong winds and tidal surges.
My Reflection For the longest time, I have been fascinated by volcanoes and the development of them. I am very excited to learn more about them and to see them first hand for myself when we're in Ecuador. After reading about the development of the Galapagos Islands and how they were made up of a chain of volcanoes has made me even more eager to explore Ecuador.
Before going to school I was always interested in animals. I have a very strong passion for protecting them and giving them the best possible life. However, I never knew of the issues that wildlife animals actually faced and the challenges they must overcome. As an environmentalist, I've been educated greatly about environmental and wildlife impacts that humans create. Reading about the wildlife in the Galapagos, especially the tortoises, sickened me. It is very sad thinking that an animal that once flourished is now facing extinction, all because of humans. Although this topic is very sad, I am still excited to visit the Galapagos Islands and learn more about the conservation actions they have put in place.
I find Mangrove forests to be very interesting. I had no idea that they provided so many environmental services. The fact that people would want to destroy these forests baffles me. If people were more aware of and actually cared about the benefits these forests could have, they may be more more inclined to protect them. I am extremely excited to visit a mangrove forest in Ecuador. Witnessing and appreciating the beauty in nature for myself is one of my favorite things to do.