Darién is a province in Panama whose capital city is La Palma. With an area of 11,896.5 km2, it is located at the eastern end of the country and bordered to the north by the province of Panamá and the region of Kuna Yala. To the south, it is bordered by Colombia. To the east, it borders Colombia; the area surrounding the border with Colombia is known as the Darién Gap, a large swath of undeveloped swampland and forest. With no roads, it is the missing link of the Pan-American Highway; the name originates from the language spoken by the indigenous Cueva, an Indian tribe destroyed by the conquistadors during the 16th century. The Tanela River, which flows toward Atrato, was Hispanicized to Darién. Santa María la Antigua del Darién, the first city founded in Tierra Firme took its name from the river. Subsequently, the region's boundaries were defined by the Gulf of Urabá. Darién Province has been inhabited by indigenous people for thousands of years. Evidence based on soil erosion suggest Slash-and-burn agriculture at the latest 4000 years ago.
Dissapearance of paleobotanical evidence of this culture coincides with the arrival of European colonists, which decimated this population. In 1508, the Spanish Crown decided to colonize the mainland, the chosen area extending from Cabo Gracias a Dios in western Central America to Cabo de la Vela, Venezuela in the east; the provinces on the mainland were Nueva Andalucía, between the Atrato River in the Gulf of Uraba and the Cabo de la Vela in Venezuela and Castilla del Oro, which stretched from the Atrato River to Cabo Gracias a Dios in Central America. The Governor of Nueva Andalucía was Alonso de Ojeda and the mayor of Castilla del Oro was Diego de Nicuesa, who became the first governor of the Isthmus of Panama. Diego de Nicuesa founded Nombre de Dios in 1510. Martin Fernandez de Enciso founded Santa Maria la Antigua del Darién, west of the Gulf of Urabá, in September 1510 on the advice of Vasco Núñez de Balboa, who had arrived at those lands earlier with Rodrigo de Bastidas. On September 1, 1513, Balboa went in search of the South Sea with 1,000 Indians.
He sighted the sea on September 25, 1513, took possession of it on September 29 in the Gulf of San Miguel. During the late 17th century there was a Scottish colonization project in the Isthmus of Panama, from which William Paterson emerged as the center of the unsuccessful attempt; the attempt to colonize by the Company of Scotland, which traded with Africa and the Indies, was part of the conflict between Spain and other 16th-century European powers in reaction to the 1494 Treaty of Tordesillas. On July 14, 1698 Paterson left with an expedition of about 1,200 on five ships from Scotland; the expedition landed October 30, 1698 in Anachucuna, a sandy bay in the north of Darien near Golden Island. It forged a "treaty of alliance and friendship" with an Indian leader, founded in Acla a colony known as New Caledonia. Paterson and his expedition withstood a Spanish force. However, diseases related to the unsanitary conditions soon decimated the expedition. In June 1699 the Scots were forced to leave New Caledonia, despite protests from Paterson, retreated to Jamaica.
A second expedition left Scotland on September 24, 1699 from Port Clyde River with four ships: the Rising Sun, Hope of Boroughstonness and Company's Hope). Paterson had a total crew of 1,300 men. On November 30, 1699 they arrived safely at the port of Caledonia, but met greater resistance from Spanish forces. On March 28, 1700, they requested; the Constitution of Panama of 1972, amended by the Reform Acts of 1978 and the Constitutional Act of 1983, has a unitary, republican and representative government. Three branches of government exist in all provinces of the Republic of Panama. Darién Province is divided into 25 corregimientos. 1 - contains the easternmost point of Central America The comarca indígena of Emberá-Wounaan was established in the province on November 8, 1983. It consists of two additional districts: Cémaco SambúThe comarca indígena of Kuna de Wargandí was established in 2000, is not subdivided into districts. Darién Province covers an area of 11,896 square kilometres, comparable to the island of Jamaica.
In the centre is an undulating plain, fed by the rivers Chucunaque and Tuira and framed by steep areas of the highlands of San Blas, Bagre and the Saltos. Among the highest mountains in the province are Tacarcuna at 2,280 metres, Piña at 1,581 metres, Pirre at 1,569 metres, Nique at 1,550 metres, Chucantí at 1,430 metres, Tanela at 1,415 metres and Upper Quia at 1,361 metres. Eight percent of the province's land is suitable for intensive cultivation, 60 percent is suitable for pasture, permanent crops and forestry production and 25 percent is protected forest reserves; the dominant natural vegetation is forests which, according to the topographic elevation and rainfall patterns, are classified as tropical moist, subtropical moist and cloud forest. Rainfall reaches 1,700 to 2,000 mm near the inlet of Garachiné, with a marked dry period between January and April. However, in the foothills and valleys of the province's interior precipi
Biodiversity refers to the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic and ecosystem level. Terrestrial biodiversity is greater near the equator, the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, is richest in the tropics; these tropical forest ecosystems cover less than 10 percent of earth's surface, contain about 90 percent of the world's species. Marine biodiversity is highest along coasts in the Western Pacific, where sea surface temperature is highest, in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity tends to cluster in hotspots, has been increasing through time, but will be to slow in the future. Rapid environmental changes cause mass extinctions. More than 99.9 percent of all species that lived on Earth, amounting to over five billion species, are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described.
More in May 2016, scientists reported that 1 trillion species are estimated to be on Earth with only one-thousandth of one percent described. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC. In July 2016, scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor of all organisms living on Earth; the age of the Earth is about 4.54 billion years. The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland. More in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia.
According to one of the researchers, "If life arose quickly on Earth.. it could be common in the universe."Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon marked a rapid growth in biodiversity via the Cambrian explosion—a period during which the majority of multicellular phyla first appeared; the next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of animal life; the Permian–Triassic extinction event, 251 million years ago, was the worst. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has attracted more attention than others because it resulted in the extinction of the dinosaurs; the period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. Named the Holocene extinction, the reduction is caused by human impacts habitat destruction.
Conversely, biodiversity positively impacts human health in a number of ways, although a few negative effects are studied. The United Nations designated 2011–2020 as the United Nations Decade on Biodiversity. 1916 - The term biological diversity was used first by J. Arthur Harris in "The Variable Desert," Scientific American, JSTOR 6182: "The bare statement that the region contains a flora rich in genera and species and of diverse geographic origin or affinity is inadequate as a description of its real biological diversity." 1975 - The term natural diversity was introduced 1980 - Thomas Lovejoy introduced the term biological diversity to the scientific community in a book.. It became used. 1985 -The contracted form biodiversity was coined by W. G. Rosen 1985 - The term "biodiversity" appears in the article, "A New Plan to Conserve the Earth's Biota" by Laura Tangley. 1988 - The term biodiversity first appeared in a publication. The present - the term has achieved widespread use. "Biodiversity" is most used to replace the more defined and long established terms, species diversity and species richness.
Biologists most define biodiversity as the "totality of genes and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and presents a unified view of the traditional types of biological variety identified: taxonomic diversity ecological diversity morphological diversity functional diversity This multilevel construct is consistent with Datman and Lovejoy. An explicit definition consistent with this interpretation was first given in a paper by Bruce A. Wilcox commissioned by the International Union for the Conservation of Nature and Natural Resources for the 1982 World National Parks Conference. Wilcox's definition was "Biological diversity is the variety of life forms...at all levels of biologi
Cordillera Central (Costa Rica)
The Cordillera Central is a volcanic mountain range in central Costa Rica which continues from the Continental Divide to east of Cordillera de Tilarán. It extends 80 km from Tapezco ending on the Pacuare River, it is separated from Cordillera de Tilarán by Platanar and Zarcero hills. The Cordillera Central is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica, it contains four large volcanoes Poás, Irazú and Turrialba. The highest peak is Irazú at 3,432 m. South of the range lie elevated plains of central tectonic depression of Costa Rican Central Valley. Cordillera Central's four main volcanoes are protected as national parks. Volcanic massif of the Poás Volcano is the central feature of Poás Volcano National Park, featuring permanent fumarolic activity. Barva Volcano features prominent hydrothermal activity and is a part of Braulio Carrillo National Park.
Irazú Volcano National Park contains the highest volcano of Costa Rica. The significant elevation of the volcano makes it a strategic site for telecommunications, many national television and radio stations have their antennas at the summit. Turrialba Volcano National Park centered on Turrialba Volcano features fumarolic activity and gas emissions
Costa Rica the Republic of Costa Rica, is a country in Central America, bordered by Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, the Pacific Ocean to the southwest, Ecuador to the south of Cocos Island. It has a population of around 5 million in a land area of 51,060 square kilometers. An estimated 333,980 people live in the capital and largest city, San José with around 2 million people in the surrounding metropolitan area; the sovereign state of Costa Rica is a unitary presidential constitutional republic. It is known for its long-standing and stable democracy, for its educated workforce, most of whom speak English; the country spends 6.9% of its budget on education, compared to a global average of 4.4%. Its economy, once dependent on agriculture, has diversified to include sectors such as finance, corporate services for foreign companies and ecotourism. Many foreign manufacturing and services companies operate in Costa Rica's Free Trade Zones where they benefit from investment and tax incentives.
Costa Rica was facing a market liquidity crisis in 2017 due to a growing budget deficit. By August 2017, the Treasury was having difficulty paying its obligations. Other challenges facing the country in its attempts to improve the economy by increasing foreign investment include a poor infrastructure and a need to improve public sector efficiency. Costa Rica was sparsely inhabited by indigenous peoples before coming under Spanish rule in the 16th century, it remained a peripheral colony of the empire until independence as part of the First Mexican Empire, followed by membership in the United Provinces of Central America, from which it formally declared independence in 1847. Since Costa Rica has remained among the most stable and progressive nations in Latin America. Following the brief Costa Rican Civil War, it permanently abolished its army in 1949, becoming one of only a few sovereign nations without a standing army; the country has performed favorably in the Human Development Index, placing 69th in the world as of 2015, among the highest of any Latin American nation.
It has been cited by the United Nations Development Programme as having attained much higher human development than other countries at the same income levels, with a better record on human development and inequality than the median of the region. Costa Rica has progressive environmental policies, it is the only country to meet all five UNDP criteria established to measure environmental sustainability. It was ranked 42nd in the world, third in the Americas, in the 2016 Environmental Performance Index, was twice ranked the best performing country in the New Economics Foundation's Happy Planet Index, which measures environmental sustainability, was identified by the NEF as the greenest country in the world in 2009. Costa Rica plans to become a carbon-neutral country by 2021. By 2016, 98.1% of its electricity was generated from green sources hydro, solar and biomass. Historians have classified the indigenous people of Costa Rica as belonging to the Intermediate Area, where the peripheries of the Mesoamerican and Andean native cultures overlapped.
More pre-Columbian Costa Rica has been described as part of the Isthmo-Colombian Area. Stone tools, the oldest evidence of human occupation in Costa Rica, are associated with the arrival of various groups of hunter-gatherers about 10,000 to 7,000 years BCE in the Turrialba Valley; the presence of Clovis culture type spearheads and arrows from South America opens the possibility that, in this area, two different cultures coexisted. Agriculture became evident in the populations, they grew tubers and roots. For the first and second millennia BCE there were settled farming communities; these were small and scattered, although the timing of the transition from hunting and gathering to agriculture as the main livelihood in the territory is still unknown. The earliest use of pottery appears around 2,000 to 3,000 BCE. Shards of pots, cylindrical vases, platters and other forms of vases decorated with grooves and some modelled after animals have been found; the impact of indigenous peoples on modern Costa Rican culture has been small compared to other nations, since the country lacked a strong native civilization to begin with.
Most of the native population was absorbed into the Spanish-speaking colonial society through inter-marriage, except for some small remnants, the most significant of which are the Bribri and Boruca tribes who still inhabit the mountains of the Cordillera de Talamanca, in the southeastern part of Costa Rica, near the frontier with Panama. The name la costa rica, meaning "rich coast" in the Spanish language, was in some accounts first applied by Christopher Columbus, who sailed to the eastern shores of Costa Rica during his final voyage in 1502, reported vast quantities of gold jewelry worn by natives; the name may have come from conquistador Gil González Dávila, who landed on the west coast in 1522, encountered natives, appropriated some of their gold. During most of the colonial period, Costa Rica was the southernmost province of the Captaincy General of Guatemala, nominally part of the Viceroyalty of New Spain. In practice, the captaincy general was a autonomous entity within the Spanish Empire.
Costa Rica's distance from the capital of the captaincy in Guatemala, its legal prohibition under Spanish law from trade with its southern neighbor Panama part of the Viceroyalty of New Granada, lack of r
Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres, definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests. Around 40% to 75% of all biotic species are indigenous to the rainforests. There may be many millions of species of plants and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered there. Rainforests are responsible for 28% of the world's oxygen turnover, sometimes misnamed oxygen production, processing it through photosynthesis from carbon dioxide and consuming it through respiration; the undergrowth in some areas of a rainforest can be restricted by poor penetration of sunlight to ground level.
If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines and small trees, called a jungle. The term jungle is sometimes applied to tropical rainforests generally. Rainforests as well as endemic rainforest species are disappearing due to deforestation, the resulting habitat loss and pollution of the atmosphere. Tropical rainforests are characterized by a warm and wet climate with no substantial dry season: found within 10 degrees north and south of the equator. Mean monthly temperatures exceed 18 °C during all months of the year. Average annual rainfall is no less than 168 cm and can exceed 1,000 cm although it lies between 175 cm and 200 cm. Many of the world's tropical forests are associated with the location of the monsoon trough known as the intertropical convergence zone; the broader category of tropical moist forests are located in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn. Tropical rainforests exist in Southeast Asia to the Philippines, Indonesia, Papua New Guinea and Sri Lanka.
Tropical forests have been called the "Earth's lungs", although it is now known that rainforests contribute little net oxygen addition to the atmosphere through photosynthesis. Tropical forests cover a large part of the globe, but temperate rainforests only occur in few regions around the world. Temperate rainforests are rainforests in temperate regions, they occur in North America, in Europe, in East Asia, in South America and in Australia and New Zealand. A tropical rainforest has a number of layers, each with different plants and animals adapted for life in that particular area. Examples include the emergent, canopy and forest floor layers; the emergent layer contains a small number of large trees called emergents, which grow above the general canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. They need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Eagles, butterflies and certain monkeys inhabit this layer.
The canopy layer contains the majority of the largest trees 30 metres to 45 metres tall. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops; the canopy, by some estimates, is home to 50 percent of all plant species. Epiphytic plants attach to trunks and branches, obtain water and minerals from rain and debris that collects on the supporting plants; the fauna is similar to that found in the emergent layer, but more diverse. A quarter of all insect species are believed to exist in the rainforest canopy. Scientists have long suspected the richness of the canopy as a habitat, but have only developed practical methods of exploring it; as long ago as 1917, naturalist William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles." True exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows.
Exploration of the canopy is still in its infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor. The science of accessing tropical forest canopy using airships or similar aerial platforms is called dendronautics; the understory or understorey layer lies between the forest floor. It is home to a number of birds and lizards, as well as predators such as jaguars, boa constrictors and leopards; the leaves are much larger at this level and insect life is abundant. Many seedlings that will grow to the canopy level are present in the understory. Only about 5% of the sunlight s
Soil erosion is the displacement of the upper layer of soil, one form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, ice, air, plants and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind erosion, zoogenic erosion, anthropogenic erosion. Soil erosion may be a slow process that continues unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil; the loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Human activities have increased by 10 -- 40 times the rate. Excessive erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses.
Water and wind erosion are the two primary causes of land degradation. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, gully erosion. Splash erosion is seen as the first and least severe stage in the soil erosion process, followed by sheet erosion rill erosion and gully erosion. In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles; the distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs.
If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope. Sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are of the order of a few centimeters or less and along-channel slopes may be quite steep; this means that rills exhibit hydraulic physics different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when runoff water accumulates and flows in narrow channels during or after heavy rains or melting snow, removing soil to a considerable depth. Valley or stream erosion occurs with continued water flow along a linear feature; the erosion is both downward, deepening the valley, headward, extending the valley into the hillside, creating head cuts and steep banks.
In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain; the stream gradient becomes nearly flat, lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood, when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone that erodes: suspended abrasive particles and boulders can act erosively as they traverse a surface, in a process known as traction. Bank erosion is the wearing away of the banks of a river; this is distinguished from changes on the bed of the watercourse, referred to as scour. Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times.
Thermal erosion is the result of weakening permafrost due to moving water. It can occur both at the coast. Rapid river channel migration observed in the Lena River of Siberia is due to thermal erosion, as these portions of the banks are composed of permafrost-cemented non-cohesive materials. Much of this erosion occurs. Thermal erosion affects the Arctic coast, where wave action and near-shore temperatures combine to undercut permafrost bluffs along the shoreline and cause them to fail. Annual erosion rates along a 100-kilometre segment of the Beaufort Sea shoreline averaged 5.6 metres per year from 1955 to 2002. At high flows, kolks, or vortices are formed by large volumes of rushing water. Kolks cause extreme local erosion, plucking bedrock and creating pothole-type geographical features called Rock-cut basins. Examples can be seen in the flood regions result from glacial Lake Missoula, which created the channeled scablands in the Columbia Basin region of eastern W
Isthmus of Panama
The Isthmus of Panama historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of the Panama Canal. Like many isthmuses, it is a location of great strategic value; the isthmus formed around 2.8 million years ago, separating the Atlantic and Pacific Oceans and causing the creation of the Gulf Stream. This was first suggested in 1910 by North American paleontologist Henry Fairfield Osborn, he based the proposal on the fossil record of mammals in Central America. This conclusion provided a foundation for Alfred Wegener when he proposed the theory of continental drift in 1912. Vasco Núñez de Balboa heard of the South Sea from natives while sailing along the Caribbean coast. On 25 September 1513 he saw the Pacific. In 1519 the town of Panamá was founded near a small indigenous settlement on the Pacific coast. After the discovery of Peru, it developed into an important port of trade and became an administrative centre.
In 1671 the Welsh pirate Henry Morgan crossed the Isthmus of Panamá from the Caribbean side and destroyed the city. The town was relocated some kilometers to the west at a small peninsula; the ruins of the old town, Panamá Viejo, are preserved and were declared a UNESCO World Heritage Site in 1997. Silver and gold from the viceroyalty of Peru were transported overland across the isthmus by Spanish Silver Train to Porto Bello, where Spanish treasure fleets shipped them to Seville and Cádiz from 1707. Lionel Wafer spent four years between 1684 among the Cuna Indians. Scotland tried to establish a settlement in 1698 through the Darien scheme; the California Gold Rush, starting in 1849, brought a large increase in the transportation of people from the Atlantic to the Pacific. Steamships brought gold diggers from eastern US ports, who trekked across the isthmus by foot and rail. On the Pacific side, they boarded. Ferdinand de Lesseps, the man behind the Suez Canal, started a Panama Canal Company in 1880 that went bankrupt in 1889 in the Panama scandals.
In 1902–4, the United States forced Colombia to grant independence to the Department of the Isthmus, bought the remaining assets of the Panama Canal Company, finished the canal in 1914. A significant body of water once separated the continents of North and South America, allowing the waters of the Pacific and Atlantic Oceans to mix freely. Beneath the surface, two plates of the Earth's crust were colliding, forcing the Cocos Plate to slide under the Caribbean Plate; the pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew large enough to form islands. Meanwhile, movement of the two tectonic plates was pushing up the sea floor forcing some areas above sea level. Over time, massive amounts of sediment from North and South America filled the gaps between the newly forming islands. Over millions of years, the sediment deposits added to the islands until the gap was filled. By no than 4.5 million years ago, an isthmus had formed between North and South America.
However, an article in Science Magazine stated that zircon crystals in middle Miocene bedrock from northern Colombia indicated that by 10 million years ago, it is that instead of islands, a full isthmus between the North and South American continents had likely formed where the Central American Seaway had been previously. Evidence suggests that the creation of this land mass and the subsequent warm, wet weather over northern Europe resulted in the formation of a large Arctic ice cap and contributed to the current ice age; that warm currents can lead to glacier formation may seem counterintuitive, but heated air flowing over the warm Gulf Stream can hold more moisture. The result is increased precipitation; the formation of the Isthmus of Panama played a major role in biodiversity on the planet. The bridge made it easier for plants to migrate between the two continents; this event is known in paleontology as the Great American Interchange. For instance, in North America, the opossum and porcupine all trace back to ancestors that came across the land bridge from South America.
Bears, dogs, horses and raccoons all made the trek south across the isthmus. As the connecting bridge between two vast land masses, the Panamanian biosphere is filled with overlapping fauna and flora from both North and South America. There are, over 978 species of birds in the isthmus area; the tropical climate encourages a myriad of large and brightly colored species, amphibians, birds and reptiles. Divided along its length by a mountain range, the isthmus's weather is wet on the Atlantic side but has a clearer division into wet and dry seasons on the Pacific side. Darien Gap Isthmo-Colombian area Postage stamps and postal history of the Canal Zone