The Geology of the Galapagos Islands
The islands are a group of volcanic islands located roughly 1000 km west of the South American coast, are thought to be the product of a mantle plume, and lie on the Nazca Plate just south of an active mid-ocean ridge called the Galapagos Spreading Center. Mantle plumes are columns of hot rock, approximately 100 km in diameter, that rise from deep within the Earth because they are hotter and less dense than the surrounding rock. The rate of ascent is about 10 cm/yr but the depth from which they rise is a matter of scientific debate. Some scientists believe that the plumes originate at shallower depths (the boundary between the upper and lower mantle at 670 km), while others believe that they come from greater depths. One idea that stems from this belief is that the mantle plume forms at the base of the Earth's mantle (2900 km in depth) where the rock layer called D" (D-double prime) is heated by the liquid core beneath it. The reasoning behind this great depth belief is that the plumes remain fixed relative to one another over many tens of millions of years even though the lithospheric plates above them move thousands of kilometers in the same time frame. As the mantle plumes reach the surface, they begin to melt as a result of decompression. The melting begins around 150 km and continues until the plume is prevented from rising any further to the surface. The lithosphere beneath the Galapagos is relatively young and thin, no more than 15 km thick, therefore the melting begins around 150 km and continues till the plume reaches 15 km. The plume, however, does not fully melt as approximately 20% of the plume melts and becomes magma. The magma is less dense than the surrounding rock and begins to rise to the surface but eventually becomes trapped in large pools called magma chambers just a few kilometers from the surface. If the magma chamber is able to force its way to the surface, a volcanic eruption occurs and successive eruptions over hundreds of years, create volcanoes. Two distinct types of volcanoes occur in the Galapagos: in the west, large volcanoes with an "inverted soup-bowl" morphology and deep calderas and in the east, smaller shield volcanoes with gentler slopes. The "inverted soup-bowl" morphology of the larger western volcanoes is unusual but not entirely unique and it's origin is not entirely certain. One hypothesis for their formation is that the distribution of eruptive vents have helped to grow the volcano outward at the bottom and upward at the top resulting in the distinct morphology. Another unusual characteristic of the western volcanoes is their large size calderas in comparison to the size of the volcano. The calderas form as a result of the collapse of underlying magma chambers and are formed after numerous episodes of collapse rather than a single event. During a geologic exploration of the islands, it was revealed that the archipelago is separated into 4 subprovinces based on the ages of the volcanoes, their geomorphic forms, and the petrology of their lavas. The first subprovince, called the "old" subprovince, is comprimised of Espanola, Santa Fe, the Baltra Islands, and the Northeastern corner of Santa Cruz. These islands in particular are remnants of ancient subaerial volcanoes however, the lava of these older volcanoes is indistinguishable from the lavas of the surrounding, younger volcanoes. The central subprovince is composed of San Cristobal, Santa Cruz, and the Santiago Islands. These islands contain volcanoes that lack a caldera, have a aligned system of satellite vents, and have relatively shallow slopes. The lavas from these islands are dominated by a magnesium oxide basalt that have a great variation in the trace elements that remain after an explosion. The western subprovince is comprised of the historically active volcanoes of Isabela and Fernandina Islands as well as the Roca Rendonda volcano. These volcanoes are the classic Galapagos shields that have roughly symmetric forms, steep slopes, and large calderas. The last subprovince, named the northern subprovince, is diverse petroloically as the range of isotopic and trace elements is encompassed by five islands: Wold, Darwin, Genovesa, Machena, and Pinta. Each island has a distinct form of volcano as Marchena and Genovesa have calderas, Wolf shows signs of an eroded caldera, and the remaining islands have none. There have been historic eruptions from many of the Galapagos volcanoes: Fernandina, Volcan Wolf, Alcedo, Sierra Negra, Cerro Azul, Santiago, Pinta, Floreana, and Marchena. Within the last ten thousand years, eruptions have also occured on Volcan Darwin, Volcan Ecuador, Genovesa, San Cristobal, and Santa Cruz. The islands of Espanola and Santa Fe are remnants of extinct volcanoes and for both, only part of the volcanic structure has been preserved as the remaining parts have faulted away. Both volcanoes have been extinct for several million years. Two small shield volcanoes, Pinzon and Rabida, have also been extinct but for about one million years. Although Santa Cruz and San Cristobal remain active, parts of their edifices are much older: more than a million years in the case of Santa Cruz and nearly two and a half million years in the case of San Cristobal.
The islands are a group of volcanic islands located roughly 1000 km west of the South American coast, are thought to be the product of a mantle plume, and lie on the Nazca Plate just south of an active mid-ocean ridge called the Galapagos Spreading Center. Mantle plumes are columns of hot rock, approximately 100 km in diameter, that rise from deep within the Earth because they are hotter and less dense than the surrounding rock. The rate of ascent is about 10 cm/yr but the depth from which they rise is a matter of scientific debate. Some scientists believe that the plumes originate at shallower depths (the boundary between the upper and lower mantle at 670 km), while others believe that they come from greater depths. One idea that stems from this belief is that the mantle plume forms at the base of the Earth's mantle (2900 km in depth) where the rock layer called D" (D-double prime) is heated by the liquid core beneath it. The reasoning behind this great depth belief is that the plumes remain fixed relative to one another over many tens of millions of years even though the lithospheric plates above them move thousands of kilometers in the same time frame. As the mantle plumes reach the surface, they begin to melt as a result of decompression. The melting begins around 150 km and continues until the plume is prevented from rising any further to the surface. The lithosphere beneath the Galapagos is relatively young and thin, no more than 15 km thick, therefore the melting begins around 150 km and continues till the plume reaches 15 km. The plume, however, does not fully melt as approximately 20% of the plume melts and becomes magma. The magma is less dense than the surrounding rock and begins to rise to the surface but eventually becomes trapped in large pools called magma chambers just a few kilometers from the surface. If the magma chamber is able to force its way to the surface, a volcanic eruption occurs and successive eruptions over hundreds of years, create volcanoes. Two distinct types of volcanoes occur in the Galapagos: in the west, large volcanoes with an "inverted soup-bowl" morphology and deep calderas and in the east, smaller shield volcanoes with gentler slopes. The "inverted soup-bowl" morphology of the larger western volcanoes is unusual but not entirely unique and it's origin is not entirely certain. One hypothesis for their formation is that the distribution of eruptive vents have helped to grow the volcano outward at the bottom and upward at the top resulting in the distinct morphology. Another unusual characteristic of the western volcanoes is their large size calderas in comparison to the size of the volcano. The calderas form as a result of the collapse of underlying magma chambers and are formed after numerous episodes of collapse rather than a single event. During a geologic exploration of the islands, it was revealed that the archipelago is separated into 4 subprovinces based on the ages of the volcanoes, their geomorphic forms, and the petrology of their lavas. The first subprovince, called the "old" subprovince, is comprimised of Espanola, Santa Fe, the Baltra Islands, and the Northeastern corner of Santa Cruz. These islands in particular are remnants of ancient subaerial volcanoes however, the lava of these older volcanoes is indistinguishable from the lavas of the surrounding, younger volcanoes. The central subprovince is composed of San Cristobal, Santa Cruz, and the Santiago Islands. These islands contain volcanoes that lack a caldera, have a aligned system of satellite vents, and have relatively shallow slopes. The lavas from these islands are dominated by a magnesium oxide basalt that have a great variation in the trace elements that remain after an explosion. The western subprovince is comprised of the historically active volcanoes of Isabela and Fernandina Islands as well as the Roca Rendonda volcano. These volcanoes are the classic Galapagos shields that have roughly symmetric forms, steep slopes, and large calderas. The last subprovince, named the northern subprovince, is diverse petroloically as the range of isotopic and trace elements is encompassed by five islands: Wold, Darwin, Genovesa, Machena, and Pinta. Each island has a distinct form of volcano as Marchena and Genovesa have calderas, Wolf shows signs of an eroded caldera, and the remaining islands have none. There have been historic eruptions from many of the Galapagos volcanoes: Fernandina, Volcan Wolf, Alcedo, Sierra Negra, Cerro Azul, Santiago, Pinta, Floreana, and Marchena. Within the last ten thousand years, eruptions have also occured on Volcan Darwin, Volcan Ecuador, Genovesa, San Cristobal, and Santa Cruz. The islands of Espanola and Santa Fe are remnants of extinct volcanoes and for both, only part of the volcanic structure has been preserved as the remaining parts have faulted away. Both volcanoes have been extinct for several million years. Two small shield volcanoes, Pinzon and Rabida, have also been extinct but for about one million years. Although Santa Cruz and San Cristobal remain active, parts of their edifices are much older: more than a million years in the case of Santa Cruz and nearly two and a half million years in the case of San Cristobal.
How Did Animals Get to the Islands?
Five to ten million years ago, the tops of the Galapagos volcanoes appeared above water for the first time but the peaks were completely devoid of plant and animal life. Since the mainland is about 600 km away from the islands, plant and animal life that are now native to the islands, arrived originally through some form of long-distance dispersal (aside from methods involving humans) such as by air and by sea. The animals that arrived by sea, were excellent swimmers as they swam their way to the islands with some help of the ocean currents. These animals were mainly sea lions, sea turtles, and penguins. Many of the reptiles and small mammals were carried from South or Central America on rafts made from vegetation. Only a handful of rafts were successful which helps to explain why there is a high diversity of reptiles, no native amphibians, and few mammals. Reptiles are best adapted to deal with the harsh salty and sunny conditions of weeks at sea leading to their high numbers among the islands. The coastal plants, like the mangroves and saltbushes, have salt tolerant seeds that can then arrive by sea as well. As for other native plants such as ferns, mosses, and lichens, their spores could have traveled by wind to the islands. Vascular plants with heavier seeds are scarce since their seeds are heavier and are therefore more difficult to move by wind with the exception of plumed seeds designed specifically for air travel. Small insects and even small snails could have easily been brought in on a breeze, and weaker-flying land birds and bats (only 2 species) more than likely arrived with the help of the wind. Sea birds that are excellent fliers over long distances, made their way to the islands by flying themselves. With these birds, hitch-hiking plant seeds could have been attached to their feet, feathers, or their guts and be brought to the islands.
Just because these organisms made it to the Galapagos doesn't mean that they were able to be productive. In order to fully establish themselves, they needed to thrive and reproduce. The plant species that were most successful were of the "weedy" variety due to the fact that they have a wide tolerance for varying environmental conditions. Another problem facing new plants on the islands was pollination. Many plants rely on insects or animals to pollinate and the chance that both the plant and pollinator arrived at the same time is very unlikely. The lack of flowering plants is a prime example of the lack of animal pollinators. However, there are many wild-pollinated plants on the islands. Over the last few centuries, humans have taken the place of birds in bringing new plants and animals to the islands. Many of the human introductions have been detrimental to established native or endemic wildlife. An example of harmful species include fire ants, goats, and blackberries that cause harm to one or more of Galapagos' iconic long-established pioneering species.
Five to ten million years ago, the tops of the Galapagos volcanoes appeared above water for the first time but the peaks were completely devoid of plant and animal life. Since the mainland is about 600 km away from the islands, plant and animal life that are now native to the islands, arrived originally through some form of long-distance dispersal (aside from methods involving humans) such as by air and by sea. The animals that arrived by sea, were excellent swimmers as they swam their way to the islands with some help of the ocean currents. These animals were mainly sea lions, sea turtles, and penguins. Many of the reptiles and small mammals were carried from South or Central America on rafts made from vegetation. Only a handful of rafts were successful which helps to explain why there is a high diversity of reptiles, no native amphibians, and few mammals. Reptiles are best adapted to deal with the harsh salty and sunny conditions of weeks at sea leading to their high numbers among the islands. The coastal plants, like the mangroves and saltbushes, have salt tolerant seeds that can then arrive by sea as well. As for other native plants such as ferns, mosses, and lichens, their spores could have traveled by wind to the islands. Vascular plants with heavier seeds are scarce since their seeds are heavier and are therefore more difficult to move by wind with the exception of plumed seeds designed specifically for air travel. Small insects and even small snails could have easily been brought in on a breeze, and weaker-flying land birds and bats (only 2 species) more than likely arrived with the help of the wind. Sea birds that are excellent fliers over long distances, made their way to the islands by flying themselves. With these birds, hitch-hiking plant seeds could have been attached to their feet, feathers, or their guts and be brought to the islands.
Just because these organisms made it to the Galapagos doesn't mean that they were able to be productive. In order to fully establish themselves, they needed to thrive and reproduce. The plant species that were most successful were of the "weedy" variety due to the fact that they have a wide tolerance for varying environmental conditions. Another problem facing new plants on the islands was pollination. Many plants rely on insects or animals to pollinate and the chance that both the plant and pollinator arrived at the same time is very unlikely. The lack of flowering plants is a prime example of the lack of animal pollinators. However, there are many wild-pollinated plants on the islands. Over the last few centuries, humans have taken the place of birds in bringing new plants and animals to the islands. Many of the human introductions have been detrimental to established native or endemic wildlife. An example of harmful species include fire ants, goats, and blackberries that cause harm to one or more of Galapagos' iconic long-established pioneering species.
Challenges in Eradicating Feral Pigs, Donkeys, and Rats from Islands
Introduced herbivores are devastating to island ecosystems. Goats, donkeys, pigs, and European rabbits have been introduced to islands worldwide causing primary and secondary impacts via overgrazing which often lead to extinction and habitat loss of native species. In the Galapagos, Santiago Island was introduced to pigs shortly after Darwin's visit in 1835. The pigs have had adverse impacts on the native biodiveristy by preying on plants, invertebrates, the eggs and hatchlings of Galapagos tortoises, lava lizards, green sea turtles, Galapagos petrels, and other native vertebrates. Pigs are thought to have played a large role, along with other introduced mammals, in the extinctions that have occurred within the archipelago. Due to the ecosystem degradation, the Galapagos National Park Service and the Charles Darwin Research station initiated a pig control program on Santiago in 1968. Hunting was sporadic and general details on the methods used were not recorded. Traps and snares were used but generally were ineffective. After 1974, hunting effort was recorded and hunters were using 0.22 caliber rifles with intermittent use of non-specialist dogs (Cruz et al, 2005). In 1985, however, hunting efforts were increased and a poisoning campaign was implemented using sodium monofluoroacetate (1080). In 1989, a revised hunting campaign was put in place and resulted in 1,869 pigs being removed and the following year, with similar efforts, 523 pigs were removed. After this, hunting effort decreased until 1995 when the increase brought forth the use of non-specialist dogs and poisoning with 1080. Between 1998 and 2000, a revised poisoning campaign was implemented and spot baiting was conducted at the end of hunting trips. The last pig was detected using spot baiting in October 2000 on the seventh monitoring trip, six months after the last shot pig and four months into extensive monitoring. For the first time in 150 years, Santiago is now free of pigs and has set the stage for future eradication programs. Pigs have been eradicated from at least 25 islands worldwide but the eradication on Santiago has been the largest accomplishment to date. Over 18,800 pigs were removed from the island as compared to the 12,000 removed from Santa Catalina Island of California. An effective poisoning campaign that worked along with a hunting program, as well as creating more access to the animals by creating trails and an intensive monitoring program, proved to be the most effective at eradicating feral pigs. In the Galapagos, feral donkeys were first recorded in the archipelago in 1834 on Floreana Island as oil seekers moved them around the archipelago for transporting tortoise oil to ships and settlements. By 1875, the island of Santiago saw large numbers of roaming donkeys and in the 1880s, the donkeys were recorded as numerous on the islands of Isabela, San Cristobal, Floreana, and Santa Cruz. On Santiago Island, there are approximately 377 vascular plant species which include six extant single-island endemics, 107 Galapagos endemics, and 48 non-native species. Goats and donkeys pose the greatest threat to this plant diversity and may be responsible for the extinction of the endemic Blutaparon rigidum. Donkeys have impacts throughout the archipelago on plant species especially the endemic Opuntia species on Alcedo and Santiago. Donkeys also impact tortoise and iguana populations with an overlapping diet and trampling nests. Feral donkey populations still exist on Santa Cruz, Floreana, and San Cristobal as well as the Sierra Negra Volcano on southern Isabela Island. On Santiago, donkeys were hunted during the pig and goat eradication campaigns and because of this, 339 donkeys were removed over three decades during varying campaigns for control and eradication. During the pig eradication campaign from 1995-1996, there was an increased hunting effort which resulted in larger numbers of donkeys being removed. According to Victor Carrion and his colleagues, the donkeys were removed from Santiago within "80 h of aerial hunting; 334 h of aerial goat hunting and 1762 hunter days since serves as monitoring to confirm their eradication" (2007). Today, Santiago and Alcedo Volcano are now free of donkeys for the first time in over 120 years. Feral donkeys have also been eradicated from at least five other islands worldwide but the removal on Sanitago and Isabela Islands are part of a massive unprecedented island conservation program. Aerial hunting of feral donkeys is highly efficient at removal in areas with open canopy. There have been great strides made worldwide toward preventing extinctions on islands with the removal of introduced mammals. Non-native herbivores, like feral donkeys, are major drivers of ecosystem change and degradation and should be routinely eradicated from islands. During European exploration and colonization before and during the 18th and 19th century, goats were introduced to islands via sailors on long sea voyages. Intentional introduction in the Galapagos occurred due to fishers. These introduced goats have had impacts on the island flora by altering the structure and composition of plant communities. Secondary impacts include habitat degradation via overgrazing. In the Galapagos, goat eradication began in 1985 but failed due to the fact that the final goats could not be detected or removed. Another eradication attempt took place in 1990 but also failed like the first. The most common eradication practice is hunting although trapping, poisoning, biocontrol, or a combination of these are other ways to eradicate. Hunting eradication practices include the use of hunting dogs and shooting from a helicopter.
Introduced herbivores are devastating to island ecosystems. Goats, donkeys, pigs, and European rabbits have been introduced to islands worldwide causing primary and secondary impacts via overgrazing which often lead to extinction and habitat loss of native species. In the Galapagos, Santiago Island was introduced to pigs shortly after Darwin's visit in 1835. The pigs have had adverse impacts on the native biodiveristy by preying on plants, invertebrates, the eggs and hatchlings of Galapagos tortoises, lava lizards, green sea turtles, Galapagos petrels, and other native vertebrates. Pigs are thought to have played a large role, along with other introduced mammals, in the extinctions that have occurred within the archipelago. Due to the ecosystem degradation, the Galapagos National Park Service and the Charles Darwin Research station initiated a pig control program on Santiago in 1968. Hunting was sporadic and general details on the methods used were not recorded. Traps and snares were used but generally were ineffective. After 1974, hunting effort was recorded and hunters were using 0.22 caliber rifles with intermittent use of non-specialist dogs (Cruz et al, 2005). In 1985, however, hunting efforts were increased and a poisoning campaign was implemented using sodium monofluoroacetate (1080). In 1989, a revised hunting campaign was put in place and resulted in 1,869 pigs being removed and the following year, with similar efforts, 523 pigs were removed. After this, hunting effort decreased until 1995 when the increase brought forth the use of non-specialist dogs and poisoning with 1080. Between 1998 and 2000, a revised poisoning campaign was implemented and spot baiting was conducted at the end of hunting trips. The last pig was detected using spot baiting in October 2000 on the seventh monitoring trip, six months after the last shot pig and four months into extensive monitoring. For the first time in 150 years, Santiago is now free of pigs and has set the stage for future eradication programs. Pigs have been eradicated from at least 25 islands worldwide but the eradication on Santiago has been the largest accomplishment to date. Over 18,800 pigs were removed from the island as compared to the 12,000 removed from Santa Catalina Island of California. An effective poisoning campaign that worked along with a hunting program, as well as creating more access to the animals by creating trails and an intensive monitoring program, proved to be the most effective at eradicating feral pigs. In the Galapagos, feral donkeys were first recorded in the archipelago in 1834 on Floreana Island as oil seekers moved them around the archipelago for transporting tortoise oil to ships and settlements. By 1875, the island of Santiago saw large numbers of roaming donkeys and in the 1880s, the donkeys were recorded as numerous on the islands of Isabela, San Cristobal, Floreana, and Santa Cruz. On Santiago Island, there are approximately 377 vascular plant species which include six extant single-island endemics, 107 Galapagos endemics, and 48 non-native species. Goats and donkeys pose the greatest threat to this plant diversity and may be responsible for the extinction of the endemic Blutaparon rigidum. Donkeys have impacts throughout the archipelago on plant species especially the endemic Opuntia species on Alcedo and Santiago. Donkeys also impact tortoise and iguana populations with an overlapping diet and trampling nests. Feral donkey populations still exist on Santa Cruz, Floreana, and San Cristobal as well as the Sierra Negra Volcano on southern Isabela Island. On Santiago, donkeys were hunted during the pig and goat eradication campaigns and because of this, 339 donkeys were removed over three decades during varying campaigns for control and eradication. During the pig eradication campaign from 1995-1996, there was an increased hunting effort which resulted in larger numbers of donkeys being removed. According to Victor Carrion and his colleagues, the donkeys were removed from Santiago within "80 h of aerial hunting; 334 h of aerial goat hunting and 1762 hunter days since serves as monitoring to confirm their eradication" (2007). Today, Santiago and Alcedo Volcano are now free of donkeys for the first time in over 120 years. Feral donkeys have also been eradicated from at least five other islands worldwide but the removal on Sanitago and Isabela Islands are part of a massive unprecedented island conservation program. Aerial hunting of feral donkeys is highly efficient at removal in areas with open canopy. There have been great strides made worldwide toward preventing extinctions on islands with the removal of introduced mammals. Non-native herbivores, like feral donkeys, are major drivers of ecosystem change and degradation and should be routinely eradicated from islands. During European exploration and colonization before and during the 18th and 19th century, goats were introduced to islands via sailors on long sea voyages. Intentional introduction in the Galapagos occurred due to fishers. These introduced goats have had impacts on the island flora by altering the structure and composition of plant communities. Secondary impacts include habitat degradation via overgrazing. In the Galapagos, goat eradication began in 1985 but failed due to the fact that the final goats could not be detected or removed. Another eradication attempt took place in 1990 but also failed like the first. The most common eradication practice is hunting although trapping, poisoning, biocontrol, or a combination of these are other ways to eradicate. Hunting eradication practices include the use of hunting dogs and shooting from a helicopter.
Galapagos Biodiversity
The Galapagos Islands have some of the highest levels of endemism anywhere on the planet and because of this, it would take forever to cover all of the flora and fauna found there. The Galapagos Conservancy website gives a good breakdown of some plants and animals with background information and fun facts and below I have reflected on a few sections.
Plants:
Unlike the mainland of Ecuador, the Galapagos islands is mainly covered by the brown and grey vegetation found in deserts due to the fact that the islands are located in the Pacific Dry Belt. To date, the islands are home to between 552 and 614 native species of vascular plants and approximately 825 introduced species. The flora can be grouped into three zones: the coastal zone, the arid zone, and the humid highlands. In the coastal zone, the plants found there are very distinctive because of their tolerance to salty conditions. Mangrove trees are the most common plant found in this zone and they serve an important role in the ecosystem as they provide shade regions for iguanas and sea lions, refuges for sea turtles, and breeding sites for many birds. The arid zone is the most extensive zone in the Galapagos. It contains plant species that are highly adapted to drought-like conditions. Succulent cacti and leafless shrubs that flower and grow in the brief rainy season are some of the dominant plants in this zone. The humid highlands are located above the dry zones and are only found on the larger, higher islands although the majority of the islands do not rise in elevation above the arid zone. Portions of this zone contain Scalesia trees which form a very dense forests as their branches are adorned with mosses, liverworts, and epiphytes (all non-parasitic plants that use larger trees for support).
Giant Tortoises:
The giant tortoises are among the most famous unique fauna in the Galapagos and although there is a great amount of variation in size and shape, there are two main morphological forms that exist: the domed carapace and the saddle-backed carapace. Domed tortoises tend to be larger in size and live on the larger islands with humid highlands where forage is abundant and easily available. The saddle-back tortoise shell evolved on arid islands in response to a lack of food during drought. The front of their carapace angles upward so that the tortoise can extend its head higher to reach vegetation. Although the tortoises have a unique adaptation that allows them to survive without food or water for up to a year, it contributed indirectly to the demise in tortoise populations. Tortoise exploitation began once buccaneers realized they could have fresh meat by storing the tortoises in the holds of the ship and they were also exploited for their oil. During the two centuries of exploitation, between 100,000 to 200,000 tortoises were lost. Three species have been extinct for some time and a fourth lost its last member, Lonesome George, in 2012. Today, it is estimated that 20,000-25,000 wild tortoises live on the islands.
Some fun facts:
The main way tortoises communicate is through behavioral actions. Males tend to make a noise when mating but females make no vocalizations. Some species of finches have developed a mutualistic relationship with the giant tortoises as they feed on ticks that hide in the folds of the tortoise's skin or on their shell. When the birds are ready to eat, they do a little dance in front of the tortoises so that they know to extend their neck for the birds to pull off the ticks. Although this video doesn't show the dance, it shows ground finches getting very close to the tortoise as though they were ready to pick off ticks.
Galapagos Iguanas (Land and Marine):
The Galapagos iguanas are thought to have a common ancestor that floated to the islands from the South American continent but the divergence between land and marine iguanas occurred around 10.5 million years ago. There are three species of land iguanas: Conolophus subcristatus, native to six islands, Conolophus pallidus, found only on the island of Santa Fe, and Colonophus marthae, the pink/rosada iguana which was first seen in 1986. Land iguanas are large (more than 3 feet long), reach maturity between 8 and 15 years, and can live for more than 50 years. They live in the drier areas of the Island and soak up the hot equatorial sunshine in the morning but seek the shade of cacti, rocks, trees, or other vegetation during the midday heat. At night they sleep in burrows to conserve their body heat. Their diet consists of low-growing plants and shrubs as well as any fallen fruits and cactus pads. Like the giant tortoises, land iguanas have a similar symbiotic relationship with finches allowing the birds to remove and eat ticks. Marine iguanas, on the other hand, are the only sea-going lizard in the world. They live, mate, and nest on the land but feed in the sea. They graze on a variety of seaweed generally on exposed rocks in subtidal areas but they also dive for seaweed when needed. They have short, blunt noses that are ideal for eating algae, a flattened tail for swimming and propelling through the water, and a special gland that is connected to their nose for expelling excess salt that is consumed. Marine iguanas show their color as they mature: the young are black while adults range from red and black, to black, green, red, and grey depending on the island. The Española marine iguanas are the most colorful and have the nickname of the "Christmas Iguanas." Interesting fact about the marine iguanas is that when they go hungry, they get thinner and shorter. It's a unique adaptation that allows the iguanas to follow the bust and booms of the El Niño cycle. The reason they get shorter is because they digest part of their bones to survive during the bust times and during the boom times, the bones grow back over a period of time while they are consuming more food.
The Galapagos Islands have some of the highest levels of endemism anywhere on the planet and because of this, it would take forever to cover all of the flora and fauna found there. The Galapagos Conservancy website gives a good breakdown of some plants and animals with background information and fun facts and below I have reflected on a few sections.
Plants:
Unlike the mainland of Ecuador, the Galapagos islands is mainly covered by the brown and grey vegetation found in deserts due to the fact that the islands are located in the Pacific Dry Belt. To date, the islands are home to between 552 and 614 native species of vascular plants and approximately 825 introduced species. The flora can be grouped into three zones: the coastal zone, the arid zone, and the humid highlands. In the coastal zone, the plants found there are very distinctive because of their tolerance to salty conditions. Mangrove trees are the most common plant found in this zone and they serve an important role in the ecosystem as they provide shade regions for iguanas and sea lions, refuges for sea turtles, and breeding sites for many birds. The arid zone is the most extensive zone in the Galapagos. It contains plant species that are highly adapted to drought-like conditions. Succulent cacti and leafless shrubs that flower and grow in the brief rainy season are some of the dominant plants in this zone. The humid highlands are located above the dry zones and are only found on the larger, higher islands although the majority of the islands do not rise in elevation above the arid zone. Portions of this zone contain Scalesia trees which form a very dense forests as their branches are adorned with mosses, liverworts, and epiphytes (all non-parasitic plants that use larger trees for support).
Giant Tortoises:
The giant tortoises are among the most famous unique fauna in the Galapagos and although there is a great amount of variation in size and shape, there are two main morphological forms that exist: the domed carapace and the saddle-backed carapace. Domed tortoises tend to be larger in size and live on the larger islands with humid highlands where forage is abundant and easily available. The saddle-back tortoise shell evolved on arid islands in response to a lack of food during drought. The front of their carapace angles upward so that the tortoise can extend its head higher to reach vegetation. Although the tortoises have a unique adaptation that allows them to survive without food or water for up to a year, it contributed indirectly to the demise in tortoise populations. Tortoise exploitation began once buccaneers realized they could have fresh meat by storing the tortoises in the holds of the ship and they were also exploited for their oil. During the two centuries of exploitation, between 100,000 to 200,000 tortoises were lost. Three species have been extinct for some time and a fourth lost its last member, Lonesome George, in 2012. Today, it is estimated that 20,000-25,000 wild tortoises live on the islands.
Some fun facts:
The main way tortoises communicate is through behavioral actions. Males tend to make a noise when mating but females make no vocalizations. Some species of finches have developed a mutualistic relationship with the giant tortoises as they feed on ticks that hide in the folds of the tortoise's skin or on their shell. When the birds are ready to eat, they do a little dance in front of the tortoises so that they know to extend their neck for the birds to pull off the ticks. Although this video doesn't show the dance, it shows ground finches getting very close to the tortoise as though they were ready to pick off ticks.
Galapagos Iguanas (Land and Marine):
The Galapagos iguanas are thought to have a common ancestor that floated to the islands from the South American continent but the divergence between land and marine iguanas occurred around 10.5 million years ago. There are three species of land iguanas: Conolophus subcristatus, native to six islands, Conolophus pallidus, found only on the island of Santa Fe, and Colonophus marthae, the pink/rosada iguana which was first seen in 1986. Land iguanas are large (more than 3 feet long), reach maturity between 8 and 15 years, and can live for more than 50 years. They live in the drier areas of the Island and soak up the hot equatorial sunshine in the morning but seek the shade of cacti, rocks, trees, or other vegetation during the midday heat. At night they sleep in burrows to conserve their body heat. Their diet consists of low-growing plants and shrubs as well as any fallen fruits and cactus pads. Like the giant tortoises, land iguanas have a similar symbiotic relationship with finches allowing the birds to remove and eat ticks. Marine iguanas, on the other hand, are the only sea-going lizard in the world. They live, mate, and nest on the land but feed in the sea. They graze on a variety of seaweed generally on exposed rocks in subtidal areas but they also dive for seaweed when needed. They have short, blunt noses that are ideal for eating algae, a flattened tail for swimming and propelling through the water, and a special gland that is connected to their nose for expelling excess salt that is consumed. Marine iguanas show their color as they mature: the young are black while adults range from red and black, to black, green, red, and grey depending on the island. The Española marine iguanas are the most colorful and have the nickname of the "Christmas Iguanas." Interesting fact about the marine iguanas is that when they go hungry, they get thinner and shorter. It's a unique adaptation that allows the iguanas to follow the bust and booms of the El Niño cycle. The reason they get shorter is because they digest part of their bones to survive during the bust times and during the boom times, the bones grow back over a period of time while they are consuming more food.
Mangrove Forests
Mangrove forests are the oldest and most resilient type of forest on Earth. They protect our coastlines and are a product of millions of years of evolution. They have adapted to saline conditions and are the most productive and diverse ecosystem. Mangrove forests are generally found in tropical and subtropical ecosystems and cover 15.2 million hectares. The tropical coastlines support the livelihoods of millions of people across the world. They grow where the ocean meets the land and form natural barriers that protect against coastal erosion and storm and wave surges. The forests stay partially submerged for a good portion of the day and once or twice a day, the tide moves out exposing the inter-tidal surface which includes the mangrove's unique aerial roots. The roots are spike-like structures called pneumatophores and are adapted to absorb air quickly as well as keeping out 90% of the salts from the water they absorb. The remaining 10% of absorbed salts is excreted typically through the leaves. Over a year, mangrove forests add 18 million metric tons to the long term storage of carbon globally. Mangroves and coral reefs have a symbiotic relationship in which the mangrove roots collect muddy sediments preventing them from smothering the coral reefs and in turn the reefs act as a barrier for storm and wave surges. The tangled mass of mangrove roots also provide an ecosystem for some reef fish in the early stages of their lives. The shallow, inter-tidal, flood path zone of the mangrove forest is a crutial support system for beginning lifeforms. It's a natural nursery ground that provides safety and nutrients for the growing young fish. During monsoon season, the rain washes nutrients from the mangrove leaves into the water and are then taken up by the growing fish. Prawns and fish nuture themselves on detritus and larvae and are able to increase nearly seven times their size in a matter of a few weeks. Many mangrove species allow their seeds to germinate while they are still attached to the tree giving them a better chance of survival. When the seeds are ready, they drop off of the tree and plant themselves in the mud or float around until they find a suitable anchor. Both of these adaptations, germinating and anchoring, allow the mangrove forests to propagate rapidly. Over the last three decades, the global areas of mangroves is shrinking due to deforestation, degradation, freshwater diversion, and conversion to other land uses such as intensive shrimp farming and agriculture. This brings more people to the coastlines and now almost 60% of the world's population lives in coastal cities and settlements. Because of this, large amounts of mangrove forests have been cut down to make way for residential areas, coastal industries, and roads. Agriculture runoff and organic and inorganic pollution caused by chemicals and heavy siltation have caused a large number of flora and fauna to die off. Some species of fish have disappeared and others are very rare. Over the last few years, importance and awareness of mangrove ecosystems has been growing. Legislative changes, protection and better management of the resources have helped to slow the degradation of the ecosystems. Restoration and preservation within local communities have helped with the mangrove ecosystems and periodic monitoring helps to identify rare species of mangroves so that they are protected. With added mangroves, there has been an increase in fish and crabs that can be caught in the area. The local communities hold regular seminars, workshops, and field visits to help spread awareness.
Mangrove forests are the oldest and most resilient type of forest on Earth. They protect our coastlines and are a product of millions of years of evolution. They have adapted to saline conditions and are the most productive and diverse ecosystem. Mangrove forests are generally found in tropical and subtropical ecosystems and cover 15.2 million hectares. The tropical coastlines support the livelihoods of millions of people across the world. They grow where the ocean meets the land and form natural barriers that protect against coastal erosion and storm and wave surges. The forests stay partially submerged for a good portion of the day and once or twice a day, the tide moves out exposing the inter-tidal surface which includes the mangrove's unique aerial roots. The roots are spike-like structures called pneumatophores and are adapted to absorb air quickly as well as keeping out 90% of the salts from the water they absorb. The remaining 10% of absorbed salts is excreted typically through the leaves. Over a year, mangrove forests add 18 million metric tons to the long term storage of carbon globally. Mangroves and coral reefs have a symbiotic relationship in which the mangrove roots collect muddy sediments preventing them from smothering the coral reefs and in turn the reefs act as a barrier for storm and wave surges. The tangled mass of mangrove roots also provide an ecosystem for some reef fish in the early stages of their lives. The shallow, inter-tidal, flood path zone of the mangrove forest is a crutial support system for beginning lifeforms. It's a natural nursery ground that provides safety and nutrients for the growing young fish. During monsoon season, the rain washes nutrients from the mangrove leaves into the water and are then taken up by the growing fish. Prawns and fish nuture themselves on detritus and larvae and are able to increase nearly seven times their size in a matter of a few weeks. Many mangrove species allow their seeds to germinate while they are still attached to the tree giving them a better chance of survival. When the seeds are ready, they drop off of the tree and plant themselves in the mud or float around until they find a suitable anchor. Both of these adaptations, germinating and anchoring, allow the mangrove forests to propagate rapidly. Over the last three decades, the global areas of mangroves is shrinking due to deforestation, degradation, freshwater diversion, and conversion to other land uses such as intensive shrimp farming and agriculture. This brings more people to the coastlines and now almost 60% of the world's population lives in coastal cities and settlements. Because of this, large amounts of mangrove forests have been cut down to make way for residential areas, coastal industries, and roads. Agriculture runoff and organic and inorganic pollution caused by chemicals and heavy siltation have caused a large number of flora and fauna to die off. Some species of fish have disappeared and others are very rare. Over the last few years, importance and awareness of mangrove ecosystems has been growing. Legislative changes, protection and better management of the resources have helped to slow the degradation of the ecosystems. Restoration and preservation within local communities have helped with the mangrove ecosystems and periodic monitoring helps to identify rare species of mangroves so that they are protected. With added mangroves, there has been an increase in fish and crabs that can be caught in the area. The local communities hold regular seminars, workshops, and field visits to help spread awareness.
References
Campbell, K. and Donlan, C.J. (2005). Feral Goat Eradications on Islands. Conservation Biology, 19, 1362-1374. doi: 10.1111/j.1523-1739.2005.00228.x
Carrion, V., Donlan, C.J., Campbell, K., Lavoie, C., and Cruz, F. (2007). Feral donkey (Equus asinus) eradications in the Galapagos. Biodiversity and Conservation, 16, 437-445. doi: 10.1007/s10531-005-5825-7
Cruz, F., Donlan, C.J., Campbell, K., and Carrion, V. (2005). Conservation action in the Galapagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation, 121, 473-478. https://doi.org/10.1016/j.biocon.2004.05.018
Galapagos Conservancy (2017). About Galapagos: Biodiversity. Available from: https://www.galapagos.org/about_galapagos/about-galapagos/biodiversity/
Galapagos Conservancy (2017). Species Arrival to Galapagos. Available from: https://www.galapagos.org/about_galapagos/about-galapagos/history/species-arrival-and-evolution/
Geist, D. and Harpp, K. (2011). The Galapagos as a Laboratory for the Earth Sciences: Field Trip Guide. Available from: http://www.webpages.uidaho.edu/~dgeist/Chapman/ChapmanFieldTripGuide.pdf
Mangroves for the Future (2012). Mangroves- Guardians of the Coast [YouTube video]. Available from: https://www.youtube.com/watch?v=4SY7X9zdZ-U&feature=youtu.be
New York Public Radio. Radiolab: Galapagos. Available from: https://www.wnyc.org/radio/#/ondemand/388850
White, W.M. (1997). Galapagos Geologyon the Web: A Brief Introduction to the Geology of the Galapagos. Available from: http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html
Campbell, K. and Donlan, C.J. (2005). Feral Goat Eradications on Islands. Conservation Biology, 19, 1362-1374. doi: 10.1111/j.1523-1739.2005.00228.x
Carrion, V., Donlan, C.J., Campbell, K., Lavoie, C., and Cruz, F. (2007). Feral donkey (Equus asinus) eradications in the Galapagos. Biodiversity and Conservation, 16, 437-445. doi: 10.1007/s10531-005-5825-7
Cruz, F., Donlan, C.J., Campbell, K., and Carrion, V. (2005). Conservation action in the Galapagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation, 121, 473-478. https://doi.org/10.1016/j.biocon.2004.05.018
Galapagos Conservancy (2017). About Galapagos: Biodiversity. Available from: https://www.galapagos.org/about_galapagos/about-galapagos/biodiversity/
Galapagos Conservancy (2017). Species Arrival to Galapagos. Available from: https://www.galapagos.org/about_galapagos/about-galapagos/history/species-arrival-and-evolution/
Geist, D. and Harpp, K. (2011). The Galapagos as a Laboratory for the Earth Sciences: Field Trip Guide. Available from: http://www.webpages.uidaho.edu/~dgeist/Chapman/ChapmanFieldTripGuide.pdf
Mangroves for the Future (2012). Mangroves- Guardians of the Coast [YouTube video]. Available from: https://www.youtube.com/watch?v=4SY7X9zdZ-U&feature=youtu.be
New York Public Radio. Radiolab: Galapagos. Available from: https://www.wnyc.org/radio/#/ondemand/388850
White, W.M. (1997). Galapagos Geologyon the Web: A Brief Introduction to the Geology of the Galapagos. Available from: http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html