Geology of the Galapagos Islands The Galapagos Islands, located at the Equator off of South America, are derived from hotspots deep inside the Earth called mantle plumes. The hot rock melts as it rises due to the pressure decrease and once at the lithosphere, it pushes it up. Some of the magma cools and thickens the crust which created the Galapagos platform. The magma that breaks the surface and continues to erupt forms the volcanoes. The Galapagos Islands are in a very geologically active region including a mid-ocean ridge (Galapagos Spreading Center), transform fault, and subduction zone. They lie below the Nazca Plate, which as it moves southeast, formed the volcanic chain of islands. The islands, however are not linear like other volcanic chains. Evidence of seamounts projects the islands in the Galapagos could have existed for 8 million years or more as older islands sank and new ones formed, which allowed for the evolution of life. Different thicknesses of the lithosphere create both the smaller, eastern volcanoes and the larger, western volcanoes on the islands. The larger volcanoes have an uncommon “inverted soup bowl” shape which makes these relatively unique though the exact reason could be due to a variety of things including the placement of vents and where the magma enters the volcano. Their large calderas, craters in the volcanoes, are also unique. From north to south, varying ages of volcanoes are found. Scientists classify the islands into old, central, western, and northern provinces based on the age of volcanoes, their features and geology. The old subprovince (Espanola, Santa Fe) consists of the remains of volcanoes that were active up to 3 million years ago. The central subprovince (San Cristobal, Santa Cruz, Santiago Islands) is characterized by more shallow volcanoes without calderas. The western subprovince ( Isabela and Fernandina) have active volcanoes that have calderas and steep slopes. Finally the northern subprovince (Wolf, Darwin,Genovesa, Marchena, and Pinta) have a variety of rock compositions with differing volcanic features. The Galapagos have a rich geological history and understanding more about their formation aids in understanding the evolution of life in this biological hotspot. Differences in rock composition, volcanic structure, age, and features exist around the islands as well as a variety of different ecosystems and biodiversity. This demonstrates the complexity of the history of this archipelago and the necessity for further research and understanding.
Species Arrival to the Galapagos Islands The biodiversity and location of the Galapagos Islands has drawn attention from all over the world. Due to their location on the equator and ocean currents, a variety of ecosystems can be seen and studied. Considering the early formation of the islands brought barren volcanoes, it is thought that species arrived by air and by sea. More aquatic animals on the island likely found their way through ocean currents while other species including reptiles could have floated on vegetation rafts to arrive there. Seed dispersal through the ocean and wind could have brought some of the vegetation we see today as well. Heavier seeds do not travel as easier which may be why low lying plants are so common on the islands. Insects, as well as birds which can transport seeds, also were aided by the wind. These factors allowed for a variety of reptiles, fewer mammals, and low lying and coastal plants. The conditions and placement of these species along with their resilience determined which were successful and which weren’t and has created the environment of the islands today. More recently, human involvement has contributed to the unwanted introduction of species that can harm the health of the Galapagos. The delicate balance and diversity of this island can be seen through its formation, which species happened to arrive and settle, and the interconnection of life there.
Challenges in eradicating feral pigs, donkeys, and goats Feral pigs, donkeys, and goats have been introduced to the Galapagos and pose a threat to the health and stability of the ecosystem as well as lead to extinction. Pigs affect both the plants and wildlife of the islands and eradicating them is necessary to save the ecosystems. Santiago Island in the Galapagos had a problem with feral pigs that we introduced in the 1800s and efforts to stop them began in 1968 and consisted of methods including hunting with guns and dogs, clearing trails, and poisoning bait. By 2000, the program intensified with spot-baiting and more intense monitoring, and the entire population on the island was wiped out, making it the largest success story of any pig eradication. Donkeys and goats were detrimental herbivores in the Galapagos as their introduction resulted in loss of flora through overgrazing. Often, these eradication efforts are not published or lack information and therefore little progress is made in the area and beyond. Those which have been published include the programs done on Santiago Island and Alcedo Volcano, found on Isabela. Both Santiago and Alcedo are rich in plant species and the presence of donkeys and goats created a great loss in biodiversity as it threatened and perhaps totally demolished some species of flora. Donkeys also posed threats to tortoises and iguanas on Alcedo as they destroyed nests and dominated resources. Aerial hunting was the method of choice for donkeys and coincided with and fueled the goat eradication campaign thus completely eliminated donkeys from Santiago and Alcedo and resulting in the later eradication of goats from Pinta Island. Judas goats, goats fitted with trackers to reveal the locations of remaining goats, were very helping in eliminating any remaining goats. This effort proved it was possible to eliminate a harmful species through strategic planning and monitoring resulting in the most productive use of conservation funds. It aided conservation on the islands and resulted in similar efforts conducted worldwide. As the program intensified, it found more success demonstrating the importance of more vigorous eradication methods. It led to more programs to eradicate invasive, harmful species including goats and donkeys and reintroduce those that were displaced. The compilation of eradication techniques and information allows for continued successes in removing harmful species and allowing ecosystems to thrive.
Galapagos Diversity The biodiversity of the Galapagos is one of its most outstanding features as it uniquely has high rates of endemism including 80% of its land bird, 97% of its reptiles, 30% of its plants, and over 20% of its marine species. However, the issues many of these species faced must be looked at to better understand how to conserve them. Though the vegetation varies in the Galapagos, many plant species are desert vegetation due to the dry belt with more tropical plants found at higher altitudes. The introduced species outweigh the native ones 825:600. Many of the introduced plant species are very invasive resulting in the need to eradicate them to protect the island’s balance. Coastal plants that tolerate salt water are found near the shore and are sanctuaries for breeding and shade. Giant tortoises in the Galapagos are one of the two giant tortoise species remaining worldwide. The two types of these tortoises are the domed carapace, which are larger and live on larger islands in their humid zones and the saddle-backed carapace, which are found on the drier islands. In the past, these tortoises were killed by hunters and pirates for their meat and by Ecuadorians for oil for lamps. Introduced species also resulted in deaths of hatchlings and competition. These factors threatened their existence. There are 3 species of land iguanas and marine iguanas. Two populations of land iguanas were greatly affected by feral dogs and had to be removed and bred as they couldn’t protect themselves. The dogs then had to be eliminated in order to return the species. The other species of land iguana, Baltra iguanas, were affected as introduced goats consumed most of their vegetation and later the U.S. air base for World War 2 and feral dogs and cats hurt their populations. Some were relocated to another island which saved the population. The marine iguana faces predators when it comes on land including birds and feral cats which affected their population. El Nino also greatly affects marine iguanas as well as an oil spill in 2001 on Santa Fe. Mammals including fur seals and rice rats also experienced population reductions. Fur seals, which are actually sea lions were hunted for their coats in the 1800s which nearly caused them to go extinct. Since then they have rebounded significantly. Three of seven rice rat species went extinct after colonization brought black rats which outcompeted and caused diseases among the populations. Finally, island birds including Galapagos penguins, flightless cormorants, petrels, and the Galapagos flamingo are affected by the changes El Nino brings, which is amplified by climate change. Galapagos petrel populations declined as their nests were exposed to cats, rats, and pigs and additionally construction and fishing affects their success.
Life in the Mangroves Mangroves are trees and shrubs that have adapted to thrive in salt water environments by expelling or blocking salt from being taken up. They are found in more tropical environments and can survive in water and in low oxygen making them both unique and irreplaceable in our global system. Over the last 20 years however, 35% of the world’s mangroves have been lost most often due to human infrastructure, industrialization, and agriculture though some natural disasters hold a small portion of accountability. Common species in these ecosystems include red, black, and white mangroves. The red mangrove is the initial colonizer of these ecosystems and its seeds can float and travel great distances to allow for dispersal. Detritus forms as leaves in the water are broken down by microorganisms and is the essential foundation in marine food chains thus outlining the importance of these ecosystems for life. Mangroves are home to a variety of organisms including horseshoe crabs, sea cucumbers, and upside down jellyfish as well as reptiles, amphibians, mammals among others. The list of the benefits mangroves provide is extensive. They serve as a breeding ground, nesting habitat, and a sanctuary for migratory birds and provide protection for organisms as less predators are found there. They also improve water quality by holding sediments in place and reducing their presence in water which allows for photosynthesis of aquatic plants to occur more efficiently. They help prevent coastal erosion and protect against storms which is important for human life. Lastly, mangroves are large carbon sinks which are essential in today’s climate for reducing greenhouse gases. Increased boating and other human interaction disturbs and threatens mangroves and their wildlife species, especially birds that nest and rely on them. Therefore, it must be limited and monitored. Mangroves provide many ecosystem services and their destruction affects not only the flora and fauna but human life and survival as well. The future of our planet requires the presence and protection of mangroves to help combat rising temperatures, sea levels, and carbon emissions.