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96-575: Its drainage basin covers a surface of 273,000 square kilometres (105,000 sq mi), which is 24% of the country's area and where 66% of its population lives. The Magdalena River is the largest river system of the northern Andes, with a length of 1,612 km. Its headwaters are in the south of Colombia, where the Andean subranges Cordillera Central and Cordillera Oriental separate, in Huila Department . The river runs east then north in

192-484: A sink , which may be a permanent lake, a dry lake , or a point where surface water is lost underground . Drainage basins are similar but not identical to hydrologic units , which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system . Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins. About 48.71% of

288-414: A watershed , though in other English-speaking places, "watershed" is used only in its original sense, that of the drainage divide line. A drainage basin's boundaries are determined by watershed delineation , a common task in environmental engineering and science. In a closed drainage basin, or endorheic basin , rather than flowing to the ocean, water converges toward the interior of the basin, known as

384-733: A ballast tank of a ship traveling from the temperate zone through tropical waters may experience temperature fluctuations as much as 20 °C. Heat challenges during transport may enhance the stress tolerance of species in their non-native range, by selecting for genotypes that will survive a second applied heat stress, such as increased ocean temperature in the founder population. Invasive species often exploit disturbances to an ecosystem ( wildfires , roads , foot trails ) to colonize an area. Large wildfires can sterilize soils, while adding nutrients . Invasive plants that can regenerate from their roots then have an advantage over natives that rely on seeds for propagation. Invasive species can affect

480-454: A drainage basin, and there are different ways to interpret that data. In the unlikely event that the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for

576-540: A drainage boundary is referred to as watershed delineation . Finding the area and extent of a drainage basin is an important step in many areas of science and engineering. Most of the water that discharges from the basin outlet originated as precipitation falling on the basin. A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network. Measurement of

672-595: A few of the traits, and that noninvasive species had these also. Common invasive species traits include fast growth and rapid reproduction , such as vegetative reproduction in plants; association with humans; and prior successful invasions. Domestic cats are effective predators; they have become feral and invasive in places such as the Florida Keys . An introduced species might become invasive if it can outcompete native species for resources. If these species evolved under great competition or predation , then

768-680: A great decrease in the population size and may constrict genetic variation , the individuals begin to show additive variance as opposed to epistatic variance. This conversion can lead to increased variance in the founding populations, which permits rapid evolution . Selection may then act on the capacity to disperse as well as on physiological tolerance to new stressors in the environment, such as changed temperature and different predators and prey. Rapid adaptive evolution through intraspecific phenotypic plasticity, pre-adaptation and post-introduction evolution lead to offspring that have higher fitness. Critically, plasticity permits changes to better suit

864-545: A great valley between the two cordilleras. It reaches the coastal plain at about nine degrees north , then runs west for about 100 km (62 mi), then north again, reaching the Caribbean Sea at the city of Barranquilla in the zone known as Bocas de Ceniza . The Magdalena River basin, which includes the Cauca River and other tributaries, are very rich in fish. As of 2008, 213 fish species were known from

960-470: A habitat in ways advantageous to other species. For example, zebra mussels increase habitat complexity on lake floors, providing crevices in which invertebrates live. This increase in complexity, together with the nutrition provided by the waste products of mussel filter-feeding , increases the density and diversity of benthic invertebrate communities. Introduced species may spread rapidly and unpredictably. When bottlenecks and founder effects cause

1056-543: A long taproot , or to live on previously uninhabited soil types. For example, barbed goatgrass was introduced to California on serpentine soils , which have low water-retention, low nutrient levels, a high magnesium / calcium ratio, and possible heavy metal toxicity. Plant populations on these soils tend to show low density, but goatgrass can form dense stands on these soils and crowd out native species. Invasive species might alter their environment by releasing chemical compounds, modifying abiotic factors, or affecting

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1152-403: A major role in exotic species introduction. High demand for the valuable Chinese mitten crab is one explanation for the possible intentional release of the species in foreign waters. Maritime trade has rapidly affected the way marine organisms are transported within the ocean; new means of species transport include hull fouling and ballast water transport. In fact, Molnar et al. 2008 documented

1248-674: A new nomenclature system based on biogeography rather than on taxa . By discarding taxonomy, human health , and economic factors, this model focused only on ecological factors. The model evaluated individual populations rather than entire species. It classified each population based on its success in that environment. This model applied equally to indigenous and to introduced species, and did not automatically categorize successful introductions as harmful. The USDA's National Invasive Species Information Center defines invasive species very narrowly. According to Executive Order 13112, " 'Invasive species' means an alien species whose introduction does or

1344-407: A number of years and then experience an explosion in population, a phenomenon known as "the lag effect". Hybrids resulting from invasive species interbreeding with native species can incorporate their genotypes into the gene pool over time through introgression . Similarly, in some instances a small invading population can threaten much larger native populations. For example, Spartina alterniflora

1440-554: A particular pest species could pollute soil and surface water. Encroachment of humans into previously remote ecosystems has exposed exotic diseases such as HIV to the wider population. Introduced birds (e.g. pigeons ), rodents and insects (e.g. mosquito , flea , louse and tsetse fly pests) can serve as vectors and reservoirs of human afflictions. Throughout recorded history, epidemics of human diseases, such as malaria , yellow fever , typhus , and bubonic plague , spread via these vectors. A recent example of an introduced disease

1536-410: A perimeter, the drainage divide , made up of a succession of elevated features, such as ridges and hills . A basin may consist of smaller basins that merge at river confluences , forming a hierarchical pattern . Other terms for a drainage basin are catchment area , catchment basin , drainage area , river basin , water basin , and impluvium . In North America, they are commonly called

1632-418: A result of either a numerical or fitness advantage of the introduced species. Genetic pollution occurs either through introduction or through habitat modification, where previously isolated species are brought into contact with the new genotypes. Invading species have been shown to adapt to their new environments in a remarkably short amount of time. The population size of invading species may remain small for

1728-548: A result of the pollution, heavy metals have also been detected in some commercially important fish in the river. As of 2002, 19 fish species in the river basin were recognized as threatened. The Magdalena River and its valley crosses a wide variety of ecosystems, like páramo in its headwaters, dry forest in the upper part of its valley, rainforest in its middle course, and swamps and wetlands in its lower course. The spectacled caiman , green iguana and brown pelican are abundant in these ecosystems but other animal species like

1824-456: Is highly fire-adapted. It spreads rapidly after burning, and increases the frequency and intensity of fires by providing large amounts of dry detritus during the fire season in western North America. Where it is widespread, it has altered the local fire regimen so much that native plants cannot survive the frequent fires, allowing it to become dominant in its introduced range. Ecological facilitation occurs where one species physically modifies

1920-623: Is likely to cause economic or environmental harm or harm to human health." Typically, an introduced species must survive at low population densities before it becomes invasive in a new location. At low population densities, it can be difficult for the introduced species to reproduce and maintain itself in a new location, so a species might reach a location multiple times before it becomes established. Repeated patterns of human movement, such as ships sailing to and from ports or cars driving up and down highways, offer repeated opportunities for establishment (a high propagule pressure ). In ecosystems ,

2016-600: Is normal, and preserves constellations of genes and genotypes. An example of this is the interbreeding of migrating coyotes with the red wolf , in areas of eastern North Carolina where the red wolf was reintroduced, reducing red wolf numbers. In South Africa's Cape Town region, analysis demonstrated that the restoration of priority source water sub-catchments through the removal of thirsty alien plant invasions (such as Australian acacias, pines and eucalyptus, and Australian black wattle) would generate expected annual water gains of 50 billion liters within 5 years compared to

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2112-581: Is now considered invasive in over 60 countries, and has invaded large geographies in several countries prompting aggressive federal efforts at attempting to control it. Primary geomorphological effects of invasive plants are bioconstruction and bioprotection. For example, kudzu ( Pueraria montana ), a vine native to Asia, was widely introduced in the southeastern United States in the early 20th century to control soil erosion . The primary geomorphological effects of invasive animals are bioturbation , bioerosion , and bioconstruction. For example, invasions of

2208-479: Is one of the most problematic invasive plant species in eastern North American forests, where it is highly invasive of the understory , reducing the growth rate of tree seedlings and threatening to modify the forest's tree composition. Native species can be threatened with extinction through the process of genetic pollution . Genetic pollution is unintentional hybridization and introgression , which leads to homogenization or replacement of local genotypes as

2304-570: Is poorly defined and often very subjective. Invasive species may be plants, animals, fungi, and microbes; some include native species that have invaded human habitats such as farms and landscapes. Some broaden the term to include indigenous or "native" species that have colonized natural areas. Some sources name Homo sapiens as an invasive species, but broad appreciation of human learning capacity and their behavioral potential and plasticity may argue against any such fixed categorization. The definition of "native" can be controversial. For example,

2400-487: Is referred to as " watershed management ". In Brazil , the National Policy of Water Resources, regulated by Act n° 9.433 of 1997, establishes the drainage basin as the territorial division of Brazilian water management. When a river basin crosses at least one political border, either a border within a nation or an international boundary, it is identified as a transboundary river . Management of such basins becomes

2496-614: Is the Dead Sea . Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. For example, the English crown gave the Hudson's Bay Company a monopoly on the fur trade in the entire Hudson Bay basin, an area called Rupert's Land . Bioregional political organization today includes agreements of states (e.g., international treaties and, within

2592-514: Is the main cause of introductions – other than for polar regions . Diseases may be vectored by invasive insects: the Asian citrus psyllid carries the bacterial disease citrus greening . The arrival of invasive propagules to a new site is a function of the site's invasibility. Many invasive species, once they are dominant in the area, become essential to the ecosystem of that area, and their removal could be harmful. Economics plays

2688-592: Is the spread of the West Nile virus , which killed humans, birds, mammals, and reptiles. The introduced Chinese mitten crabs are carriers of Asian lung fluke . Waterborne disease agents, such as cholera bacteria ( Vibrio cholerae ), and causative agents of harmful algal blooms are often transported via ballast water. Globally, invasive species management and control are substantial economic burdens, with expenditures reaching approximately $ 1.4 trillion annually. The economic impact of invasive alien species alone

2784-713: The African Great Lakes , the interiors of Australia and the Arabian Peninsula , and parts in Mexico and the Andes . Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins. In endorheic bodies of water where evaporation is the primary means of water loss, the water is typically more saline than the oceans. An extreme example of this

2880-489: The Age of Discovery , and accelerating again with international trade . Notably invasive plant species include the kudzu vine, giant hogweed , Japanese knotweed , and yellow starthistle . Notably invasive animals include European rabbits , domestic cats , and carp . Invasive species are the subset of established non-native alien or naturalized species that are a threat to native species and biodiversity. The term "invasive"

2976-828: The Continental Divide , northern Alaska and parts of North Dakota , South Dakota , Minnesota , and Montana in the United States, the north shore of the Scandinavian peninsula in Europe, central and northern Russia, and parts of Kazakhstan and Mongolia in Asia , which totals to about 17% of the world's land. Just over 13% of the land in the world drains to the Pacific Ocean . Its basin includes much of China, eastern and southeastern Russia, Japan,

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3072-522: The Great Lakes via ballast water. These outcompete native organisms for oxygen and food, and can be transported in the small puddle left in a supposedly empty ballast tank. Regulations attempt to mitigate such risks, not always successfully. Climate change is causing an increase in ocean temperature . This in turn will cause range shifts in organisms, which could harm the environment as new species interactions occur. For example, organisms in

3168-714: The Korean Peninsula , most of Indochina, Indonesia and Malaysia, the Philippines, all of the Pacific Islands , the northeast coast of Australia , and Canada and the United States west of the Continental Divide (including most of Alaska), as well as western Central America and South America west of the Andes. The Indian Ocean 's drainage basin also comprises about 13% of Earth's land. It drains

3264-541: The West Indian manatee , Magdalena tinamou , Todd's parakeet , American crocodile , Colombian slider , Magdalena River turtle , Dahl's toad-headed turtle and red-footed tortoise are in danger of extinction. In addition, there is a possible risk posed by invasive hippopotamus . Originally imported by Pablo Escobar , these hippopotami became feral following his demise, and have since expanded beyond their original home on Hacienda Napoles into nearby regions of

3360-599: The economic returns from invasive species are far less than the costs they impose. In the Great Lakes region the sea lamprey is an invasive species. In its original habitat, it had co-evolved as a parasite that did not kill its host. However, in the Great Lakes Region, it acts as a predator and can consume up to 40 pounds of fish in its 12–18 month feeding period. Sea lampreys prey on all types of large fish such as lake trout and salmon . The sea lampreys' destructive effects on large fish negatively affect

3456-844: The extinction of species, loss in biodiversity, and loss of ecosystem services , costs from impacts of invasive species would drastically increase. It is often argued that the key to invasive species management is early detection and rapid response. However, early response only helps when the invasive species is not frequently reintroduced into the managed area, and the cost of response is affordable. Weeds reduce yield in agriculture . Many weeds are accidental introductions that accompany imports of commercial seeds and plants. Introduced weeds in pastures compete with native forage plants, threaten young cattle (e.g., leafy spurge, Euphorbia virgata ) or are unpalatable because of thorns and spines (e.g., yellow starthistle ). Forage loss from invasive weeds on pastures amounts to nearly US$ 1 billion in

3552-577: The groundwater . A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. Invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions , causing ecological, environmental, and/or economic damage. The term can also be used for native species that become harmful to their native environment after human alterations to its food web . Since

3648-744: The spatial scale of invasion studies. Small-scale studies tended to show a negative relationship between diversity and invasion, while large-scale studies tended to show the reverse, perhaps a side-effect of invasives' ability to capitalize on increased resource availability and weaker species interactions that are more common when larger samples are considered. However, this pattern does not seem to hold true for invasive vertebrates. Island ecosystems may be more prone to invasion because their species face few strong competitors and predators, and because their distance from colonizing species populations makes them more likely to have "open" niches. For example, native bird populations on Guam have been decimated by

3744-445: The 20th century, invasive species have become serious economic, social, and environmental threats worldwide. Invasion of long-established ecosystems by organisms is a natural phenomenon, but human-facilitated introductions have greatly increased the rate, scale, and geographic range of invasion. For millennia, humans have served as both accidental and deliberate dispersal agents, beginning with their earliest migrations , accelerating in

3840-477: The 958 endangered species under the Endangered Species Act are at risk. The unintentional introduction of forest pest species and plant pathogens can change forest ecology and damage the timber industry . Overall, forest ecosystems in the U.S. are widely invaded by exotic pests, plants, and pathogens. The Asian long-horned beetle ( Anoplophora glabripennis ) was first introduced into

3936-524: The California sea otter ( Enhydra lutris ). Invasive species appear to have specific traits or specific combinations of traits that allow them to outcompete native species . In some cases, the competition is about rates of growth and reproduction. In other cases, species interact with each other more directly. One study found that 86% of invasive species could be identified from such traits alone. Another study found that invasive species often had only

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4032-498: The Chinese mitten crab ( Eriocheir sinensis ) have resulted in higher bioturbation and bioerosion rates. A native species can become harmful and effectively invasive to its native environment after human alterations to its food web . This has been the case with the purple sea urchin ( Strongylocentrotus purpuratus ), which has decimated kelp forests along the northern California coast due to overharvesting of its natural predator,

4128-593: The Magdalena River and the Sierra Nevada de Santa Marta mountain range. The General in His Labyrinth , by Gabriel García Márquez, is a fictionalized account of the final voyage of Simón Bolívar down the Magdalena River, where he revisits many cities and villages along the river. In Magdalena: River of Dreams (Knopf, 2020), Canadian writer, anthropologist, and explorer Wade Davis travels

4224-565: The Magdalena River. Due to its geographical position in the north of South America , the Magdalena River was since precolumbian times a route towards the interior of present-day Colombia and Ecuador . Several Carib -speaking peoples such as the Panche and the Yariguí ascended through the western bank of the river, while its eastern portion was inhabited by the Muisca civilization, which called

4320-609: The Magdalena River. In 1825, the Congress of Colombia awarded a concession to establish steam navigation in the Magdalena River to Juan Bernardo Elbers, but his company closed shortly after. By 1845, steamboats regularly travelled on the river until 1961, when the last steamers ceased operation. Much of the film Love in the Time of Cholera takes place in the historic, walled city of Cartagena in Colombia. Some screenshots showed

4416-522: The U.S. A decline in pollinator services and loss of fruit production has been caused by honey bees infected by the invasive varroa mite . Introduced rats ( Rattus rattus and R. norvegicus ) have become serious pests on farms, destroying stored grains. The introduction of leaf miner flies ( Agromyzidae ), including the American serpentine leaf miner ( Liriomyza trifolii ), to California has caused losses in California's floriculture industry, as

4512-549: The U.S. in 1996, and was expected to infect and damage millions of acres of hardwood trees. As of 2005 thirty million dollars had been spent in attempts to eradicate this pest and protect millions of trees in the affected regions. The woolly adelgid has inflicted damage on old-growth spruce, fir and hemlock forests and damages the Christmas tree industry. Chestnut blight and Dutch elm disease are plant pathogens with serious impacts. Garlic mustard, Alliaria petiolata ,

4608-623: The US, interstate compacts ) or other political entities in a particular drainage basin to manage the body or bodies of water into which it drains. Examples of such interstate compacts are the Great Lakes Commission and the Tahoe Regional Planning Agency . In hydrology , the drainage basin is a logical unit of focus for studying the movement of water within the hydrological cycle . The process of finding

4704-591: The alteration in ecosystem functionality (due to homogenization of biota communities), invasive species have resulted in negative effects on human well-being, which includes reduced resource availability, unrestrained spread of human diseases, recreational and educational activities, and tourism. Alien species have caused diseases including human immunodeficiency virus (HIV), monkey pox , and severe acute respiratory syndrome (SARS). Invasive species and accompanying control efforts can have long term public health implications. For instance, pesticides applied to treat

4800-621: The ancestors of Equus ferus (modern horses) evolved in North America and radiated to Eurasia before becoming extinct in North America. Upon being introduced to North America in 1493 by Spanish conquistadors , it is debatable whether the feral horses were native or exotic to the continent of their evolutionary ancestors. While invasive species can be studied within many subfields of biology, most research on invasive organisms has been in ecology and biogeography . Much of

4896-478: The availability of resources determines the impact of additional species on the ecosystem. Stable ecosystems have a resource equilibrium, which can be changed fundamentally by the arrival of invasive species. When changes such as a forest fire occur, normal ecological succession favors native grasses and forbs . An introduced species that can spread faster than natives can outcompete native species for food, squeezing them out. Nitrogen and phosphorus are often

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4992-425: The basin, but there has been a drastic decrease in the annual harvest with a fall of about 90% between 1975 and 2008. The primary threats are pollution (such as human waste, mining, farming and deforestation causing siltation ) and habitat loss (such a dams ). Additional dams are being constructed, including El Quimbo (opened in 2015) and Ituango (expected operational in 2018), which has caused some controversy. As

5088-406: The basin, it can form tributaries that change the structure of the land. There are three different main types, which are affected by the rocks and ground underneath. Rock that is quick to erode forms dendritic patterns, and these are seen most often. The two other types of patterns that form are trellis patterns and rectangular patterns. Rain gauge data is used to measure total precipitation over

5184-509: The basin. Since then several new species have been described from the basin such as five Hemibrycon in 2013, two Ancistrus in 2013 and a Farlowella in 2014. Among the more famous species in the basin are Kronoheros umbriferus , Ctenolucius hujeta , Geophagus steindachneri , Ichthyoelephas longirostris , Panaque cochliodon , Pimelodus blochii , Potamotrygon magdalenae , Prochilodus magdalenae , Pseudoplatystoma magdaleniatum and Salminus affinis . About 55% of

5280-467: The behaviour of herbivores , impacting on other species. Some, like Kalanchoe daigremontana , produce allelopathic compounds that inhibit competitors. Others like Stapelia gigantea facilitate the growth of seedlings of other species in arid environments by providing appropriate microclimates and preventing herbivores from eating seedlings. Changes in fire regimens are another form of facilitation. Bromus tectorum , originally from Eurasia,

5376-507: The business-as-usual scenario (which is important as Cape Town experiences significant water scarcity ). This is the equivalent to one-sixth of the city's current supply needs. These annual gains will double within 30 years. The catchment restoration is significantly more cost-effective then other water augmentation solutions (1/10 the unit cost of alternative options). A water fund has been established, and these exotic species are being eradicated. Invasive species can affect human health. With

5472-511: The densities of native forage plants, declining the habitat-use by wild herbivores and threatening the long-term sustenance of dependent carnivores, including the tiger . Invasive species can change the functions of ecosystems. For example, invasive plants can alter the fire regime (cheatgrass, Bromus tectorum ), nutrient cycling (smooth cordgrass Spartina alterniflora ), and hydrology ( Tamarix ) in native ecosystems. Invasive species that are closely related to rare native species have

5568-430: The discharge of water from a basin may be made by a stream gauge located at the basin's outlet. Depending on the conditions of the drainage basin, as rainfall occurs some of it seeps directly into the ground. This water will either remain underground, slowly making its way downhill and eventually reaching the basin, or it will permeate deeper into the soil and consolidate into groundwater aquifers. As water flows through

5664-441: The drainage area is dependent on the soil type. Certain soil types such as sandy soils are very free-draining, and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing clay can be almost impermeable and therefore rainfall on clay soils will run off and contribute to flood volumes. After prolonged rainfall even free-draining soils can become saturated , meaning that any further rainfall will reach

5760-697: The drainage basin to the mouth, and may accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material. Because drainage basins are coherent entities in a hydrological sense, it has become common to manage water resources on the basis of individual basins. In the U.S. state of Minnesota , governmental entities that perform this function are called " watershed districts ". In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called conservation authorities . In North America, this function

5856-857: The eastern coast of Africa, the coasts of the Red Sea and the Persian Gulf , the Indian subcontinent , Burma, and most parts of Australia . The five largest river basins (by area), from largest to smallest, are those of the Amazon (7 million km ), the Congo (4 million km ), the Nile (3.4 million km ), the Mississippi (3.22 million km ), and the Río de la Plata (3.17 million km ). The three rivers that drain

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5952-436: The expense to monitor, control, manage, and research invasive weed species is approximately AU$ 116.4 million per year, with costs directed solely to central and local government. While in some cases, invasive species may offer economic benefits, such as the potential for commercial forestry from invasive trees, these benefits are generally overshadowed by the substantial costs associated with biological invasions. In most cases,

6048-563: The field lacks any official designation but is commonly referred to as "invasion ecology" or more generally "invasion biology". This lack of standard terminology has arisen due to the interdisciplinary nature of the field which borrows terms from disciplines such as agriculture , zoology , and pathology , as well as due to studies being performed in isolation. In an attempt to avoid the ambiguous, subjective, and pejorative vocabulary that so often accompanies discussion of invasive species even in scientific papers, Colautti and MacIsaac proposed

6144-478: The fish species in the basin are endemic , including four endemic genera : The catfish Centrochir and Eremophilus , and the characids Carlastyanax (often included in Astyanax ) and Genycharax . In general, the fish fauna shows connections with surrounding basins, notably Atrato and Maracaibo , but to a lesser extent also Amazon – Orinoco . The most productive fishing areas in Colombia are in

6240-629: The fishing industry and have helped cause the collapse of the population of some species. Economic costs from invasive species can be separated into direct costs through production loss in agriculture and forestry, and management costs. Estimated damage and control costs of invasive species in the U.S. amount to more than $ 138 billion annually. Economic losses can occur through loss of recreational and tourism revenues. When economic costs of invasions are calculated as production loss and management costs, they are low because they do not consider environmental damage; if monetary values were assigned to

6336-446: The governments of California and New Zealand have announced more stringent control for vessel hull fouling within their respective jurisdictions. Another vector of non-native aquatic species is ballast water taken up at sea and released in port by transoceanic vessels. Some 10,000 species are transported via ballast water each day. Many of these are harmful. For example, freshwater zebra mussels from Eurasia most likely reached

6432-583: The greatest portion of western Sub-Saharan Africa , as well as Western Sahara and part of Morocco . The two major mediterranean seas of the world also flow to the Atlantic. The Caribbean Sea and Gulf of Mexico basin includes most of the U.S. interior between the Appalachian and Rocky Mountains , a small part of the Canadian provinces of Alberta and Saskatchewan , eastern Central America ,

6528-435: The ground and along rivers it can pick up nutrients , sediment , and pollutants . With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water body . Modern use of artificial fertilizers , containing nitrogen (as nitrates ), phosphorus , and potassium , has affected the mouths of drainage basins. The minerals are carried by

6624-781: The ground at its terminus, the area can go by several names, such playa, salt flat, dry lake , or alkali sink . The largest endorheic basins are in Central Asia , including the Caspian Sea , the Aral Sea , and numerous smaller lakes. Other endorheic regions include the Great Basin in the United States, much of the Sahara Desert , the drainage basin of the Okavango River ( Kalahari Basin ), highlands near

6720-489: The individual to its environment. Pre-adaptations and evolution after the introduction reinforce the success of the introduced species. The enemy release hypothesis states that evolution leads to ecological balance in every ecosystem. No single species can occupy a majority of an ecosystem due to the presences of competitors, predators, and diseases. Introduced species moved to a novel habitat can become invasive, with rapid population growth, when these controls do not exist in

6816-636: The introductions of the amethyst gem clam and the European green crab . The gem clam was introduced into California's Bodega Harbor from the US East Coast a century ago. On its own, it never displaced native clams ( Nutricola spp.). In the mid-1990s, the introduction of the European green crab resulted in an increase of the amethyst gem at the expense of the native clams. In India, multiple invasive plants have invaded 66% of natural areas, reducing

6912-538: The invaded habitats and bioregions adversely, causing ecological, environmental, or economic damage. The European Union defines "Invasive Alien Species" as those that are outside their natural distribution area, and that threaten biological diversity . Biotic invasion is one of the five top drivers for global biodiversity loss , and is increasing because of tourism and globalization . This may be particularly true in inadequately regulated fresh water systems, though quarantines and ballast water rules have improved

7008-646: The invasive brown tree snake . In New Zealand the first invasive species were the dogs and rats brought by Polynesian settlers around 1300. These and other introductions devastated endemic New Zealand species. The colonization of Madagascar brought similar harm to its ecosystems. Logging has caused harm directly by destroying habitat, and has allowed non-native species such as prickly pear and silver wattle to invade. The water hyacinth forms dense mats on water surfaces, limiting light penetration and hence harming aquatic organisms, and causing substantial management costs. The shrub lantana ( Lantana camara )

7104-639: The islands of the Caribbean and the Gulf, and a small part of northern South America. The Mediterranean Sea basin, with the Black Sea , includes much of North Africa , east-central Africa (through the Nile River ), Southern , Central, and Eastern Europe , Turkey , and the coastal areas of Israel , Lebanon , and Syria . The Arctic Ocean drains most of Western Canada and Northern Canada east of

7200-406: The length of the river by boat, on foot, by car, and on horseback combining descriptions of nature with episodes from Colombian history. Drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth , or flows into another body of water , such as a lake or ocean . A basin is separated from adjacent basins by

7296-443: The limiting factors in these situations. Every species occupies an ecological niche in its native ecosystem; some species fill large and varied roles, while others are highly specialized. Invading species may occupy unused niches, or create new ones. For example, edge effects describe what happens when part of an ecosystem is disturbed, as when land is cleared for agriculture . The boundary between remaining undisturbed habitat and

7392-514: The most water, from most to least, are the Amazon, Ganges , and Congo rivers. Endorheic basin are inland basins that do not drain to an ocean. Endorheic basins cover around 18% of the Earth's land. Some endorheic basins drain to an Endorheic lake or Inland sea . Many of these lakes are ephemeral or vary dramatically in size depending on climate and inflow. If water evaporates or infiltrates into

7488-635: The new ecosystem. Non-native species have many vectors , but most are associated with human activity. Natural range extensions are common, but humans often carry specimens faster and over greater distances than natural forces. An early human vector occurred when prehistoric humans introduced the Pacific rat ( Rattus exulans ) to Polynesia. Vectors include plants or seeds imported for horticulture . The pet trade moves animals across borders, where they can escape and become invasive. Organisms stow away on transport vehicles. Incidental human assisted transfer

7584-523: The new environment may host fewer able competitors, allowing the invader to proliferate. Ecosystems used to their fullest capacity by native species can be modeled as zero-sum systems, in which any gain for the invader is a loss for the native. However, such unilateral competitive superiority (and extinction of native species with increased populations of the invader) is not the rule. An invasive species might be able to use resources previously unavailable to native species, such as deep water accessed by

7680-528: The newly cleared land itself forms a distinct habitat, creating new winners and losers and possibly hosting species that would not thrive outside the boundary habitat. In 1958, Charles S. Elton claimed that ecosystems with higher species diversity were less subject to invasive species because fewer niches remained unoccupied. Other ecologists later pointed to highly diverse, but heavily invaded ecosystems, arguing that ecosystems with high species diversity were more susceptible to invasion. This debate hinged on

7776-476: The pathways of hundreds of marine invasive species and found that shipping was the dominant mechanism for the transfer of invasive species. Many marine organisms can attach themselves to vessel hulls. Such organisms are easily transported from one body of water to another, and are a significant risk factor for a biological invasion event. Controlling for vessel hull fouling is voluntary and there are no regulations currently in place to manage hull fouling. However,

7872-472: The potential to hybridize with the native species. Harmful effects of hybridization have led to a decline and even extinction of native species. For example, hybridization with introduced cordgrass, Spartina alterniflora , threatens the existence of California cordgrass ( Spartina foliosa ) in San Francisco Bay . Invasive species cause competition for native species and because of this 400 of

7968-418: The rainfall on the area of land included in its polygon. These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons. The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map. Calculating the area between these curves and adding up the volume of water is time-consuming. Isochrone maps can be used to show

8064-631: The responsibility of the countries sharing it. Nile Basin Initiative , OMVS for Senegal River , Mekong River Commission are a few examples of arrangements involving management of shared river basins. Management of shared drainage basins is also seen as a way to build lasting peaceful relationships among countries. The catchment is the most significant factor determining the amount or likelihood of flooding . Catchment factors are: topography , shape, size, soil type, and land use (paved or roofed areas). Catchment topography and shape determine

8160-747: The river Yuma . Likewise, the Spanish conquistadores who arrived to today's Colombia early in the 16th century used the river to push to the wild and mountainous inland after Rodrigo de Bastidas discovered and named the river on April 1, 1501. During the Spanish colonization of the Americas , the river was the only transport link communicating Bogotá with the Caribbean Sea port Cartagena de Indias and thus with Europe. The Magdalena Campaign of Pierre Labatut and Simón Bolívar took place along

8256-461: The river rather than being absorbed by the ground. If the surface is impermeable the precipitation will create surface run-off which will lead to higher risk of flooding; if the ground is permeable, the precipitation will infiltrate the soil. Land use can contribute to the volume of water reaching the river, in a similar way to clay soils. For example, rainfall on roofs, pavements , and roads will be collected by rivers with almost no absorption into

8352-412: The situation. Invasive species may drive local native species to extinction via competitive exclusion, niche displacement, or hybridisation with related native species. Therefore, besides their economic ramifications, alien invasions may result in extensive changes in the structure, composition and global distribution of the biota at sites of introduction, leading ultimately to the homogenisation of

8448-418: The speed with which the runoff reaches a river. A long thin catchment will take longer to drain than a circular catchment. Size will help determine the amount of water reaching the river, as the larger the catchment the greater the potential for flooding. It is also determined on the basis of length and width of the drainage basin. Soil type will help determine how much water reaches the river. The runoff from

8544-499: The spread of biological invasions, mitigate further impacts, and restore affected ecosystems. For example, the damage caused by 79 invasive species between 1906 and 1991 in the United States has been estimated at US$ 120 billion. Similarly, in China , invasive species have been reported to reduce the country's gross domestic product (GDP) by 1.36% per year. The management of biological invasions can be costly. In Australia , for instance,

8640-415: The time taken for rain to reach the river, while catchment size, soil type, and development determine the amount of water to reach the river. Generally, topography plays a big part in how fast runoff will reach a river. Rain that falls in steep mountainous areas will reach the primary river in the drainage basin faster than flat or lightly sloping areas (e.g., > 1% gradient). Shape will contribute to

8736-477: The time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. Drainage basins are the principal hydrologic unit considered in fluvial geomorphology . A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms. Drainage basins are important in ecology . As water flows over

8832-502: The work has been influenced by Charles Elton's 1958 book The Ecology of Invasion by Animals and Plants which creates a generalized picture of biological invasions. Studies remained sparse until the 1990s. This research, largely field observational studies, has disproportionately been concerned with terrestrial plants . The rapid growth of the field has driven a need to standardize the language used to describe invasive species and events. Despite this, little standard terminology exists;

8928-405: The world's fauna and flora and the loss of biodiversity . It is difficult to unequivocally attribute extinctions to a species invasion, though there is for example strong evidence that the extinction of about 90 amphibian species was caused by the chytrid fungus spread by international trade. Multiple successive introductions of different non-native species can worsen the total effect, as with

9024-673: The world's land drains to the Atlantic Ocean . In North America , surface water drains to the Atlantic via the Saint Lawrence River and Great Lakes basins, the Eastern Seaboard of the United States, the Canadian Maritimes , and most of Newfoundland and Labrador . Nearly all of South America east of the Andes also drains to the Atlantic, as does most of Western and Central Europe and

9120-416: Was estimated to exceed $ 423 billion annually as of 2019. This cost has exhibited a significant increase, quadrupling every decade since 1970, underscoring the escalating financial implications of these biological invasions. Invasive species contribute to ecological degradation , altering ecosystem functionality and reducing the services ecosystems provide. This necessitates additional expenditures to control

9216-470: Was introduced in the San Francisco Bay and hybridized with native Spartina foliosa . The higher pollen count and male fitness of the invading species resulted in introgression that threatened the native populations due to lower pollen counts and lower viability of the native species. Reduction in fitness is not always apparent from morphological observations alone. Some degree of gene flow

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