An invasive species is a species, not native to a specific location, that has a tendency to spread to a degree believed to cause damage to the environment, human economy or human health. The criteria for invasive species has been controversial, as divergent perceptions exist among researchers as well as concerns with the subjectivity of the term "invasive". Several alternate usages of the term have been proposed; the term as most used applies to introduced species that adversely affect the habitats and bioregions they invade economically, environmentally, or ecologically. Such invasive species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland–urban interface land from loss of natural controls; this includes non-native invasive plant species labeled as exotic pest plants and invasive exotics growing in native plant communities. It has been used in this sense by government organizations as well as conservation groups such as the International Union for Conservation of Nature and the California Native Plant Society.
The European Union defines "Invasive Alien Species" as those that are, outside their natural distribution area, secondly, threaten biological diversity. The term is used by land managers, researchers, horticulturalists and the public for noxious weeds; the kudzu vine, Andean pampas grass, yellow starthistle are examples. An alternate usage broadens the term to include indigenous or "native" species along with non-native species, that have colonized natural areas. Deer are an example, considered to be overpopulating their native zones and adjacent suburban gardens, by some in the Northeastern and Pacific Coast regions of the United States. Sometimes the term is used to describe a non-native or introduced species that has become widespread. However, not every introduced. A nonadverse example is the common goldfish, found throughout the United States, but achieves high densities. Notable examples of invasive species include European rabbits, grey squirrels, domestic cats and ferrets. Dispersal and subsequent proliferation of species is not an anthropogenic phenomenon.
There are many mechanisms by which species from all Kingdoms have been able to travel across continents in short periods of time such as via floating rafts, or on wind currents. Charles Darwin, a British naturalist, performed many experiments to better understand long distance seed dispersal, was able to germinate seeds from insect frass, faeces of waterfowl, dirt clods on the feet of birds, all of which may have traveled significant distances under their own power, or be blown off course by thousands of miles. Invasion of long-established ecosystems by organisms from distant bio-regions is a natural phenomenon, accelerated via hominid-assisted migration although this has not been adequately directly measured; the definition of "native" is controversial in that there is no way to determine nativity. For example, the ancestors of Equus ferus evolved in North America and radiated to Eurasia before becoming locally extinct. Upon returning to North America in 1493 during their hominid-assisted migration, it is debatable as to whether they were native or exotic to the continent of their evolutionary ancestors.
Scientists include species and ecosystem factors among the mechanisms that, when combined, establish invasiveness in a newly introduced species. While all species compete to survive, 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 reproduction. In other cases, species interact with each other more directly. Researchers disagree about the usefulness of traits as invasiveness markers. One study found that of a list of invasive and noninvasive species, 86% of the invasive species could be identified from the traits alone. Another study found invasive species tended to have only a small subset of the presumed traits and that many similar traits were found in noninvasive species, requiring other explanations. Common invasive species traits include the following: Fast growth Rapid reproduction High dispersal ability Phenotype plasticity Tolerance of a wide range of environmental conditions Ability to live off of a wide range of food types Association with humans Prior successful invasionsTypically, 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. An introduced species might become invasive if it can outcompete native species for resources such as nutrients, physical space, water, or food. If these species evolved under great competition or predation the new environment may host fewer able competitors, allowing the invader to proliferate quickly. Ecosystems which are being 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, su
Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering 9.98 million square kilometres, making it the world's second-largest country by total area. Canada's southern border with the United States is the world's longest bi-national land border, its capital is Ottawa, its three largest metropolitan areas are Toronto and Vancouver. As a whole, Canada is sparsely populated, the majority of its land area being dominated by forest and tundra, its population is urbanized, with over 80 percent of its inhabitants concentrated in large and medium-sized cities, many near the southern border. Canada's climate varies across its vast area, ranging from arctic weather in the north, to hot summers in the southern regions, with four distinct seasons. Various indigenous peoples have inhabited what is now Canada for thousands of years prior to European colonization. Beginning in the 16th century and French expeditions explored, settled, along the Atlantic coast.
As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces; this began an accretion of provinces and territories and a process of increasing autonomy from the United Kingdom. This widening autonomy was highlighted by the Statute of Westminster of 1931 and culminated in the Canada Act of 1982, which severed the vestiges of legal dependence on the British parliament. Canada is a parliamentary democracy and a constitutional monarchy in the Westminster tradition, with Elizabeth II as its queen and a prime minister who serves as the chair of the federal cabinet and head of government; the country is a realm within the Commonwealth of Nations, a member of the Francophonie and bilingual at the federal level. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, education.
It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Canada's long and complex relationship with the United States has had a significant impact on its economy and culture. A developed country, Canada has the sixteenth-highest nominal per capita income globally as well as the twelfth-highest ranking in the Human Development Index, its advanced economy is the tenth-largest in the world, relying chiefly upon its abundant natural resources and well-developed international trade networks. Canada is part of several major international and intergovernmental institutions or groupings including the United Nations, the North Atlantic Treaty Organization, the G7, the Group of Ten, the G20, the North American Free Trade Agreement and the Asia-Pacific Economic Cooperation forum. While a variety of theories have been postulated for the etymological origins of Canada, the name is now accepted as coming from the St. Lawrence Iroquoian word kanata, meaning "village" or "settlement".
In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona. Cartier used the word Canada to refer not only to that particular village but to the entire area subject to Donnacona. From the 16th to the early 18th century "Canada" referred to the part of New France that lay along the Saint Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named the Canadas. Upon Confederation in 1867, Canada was adopted as the legal name for the new country at the London Conference, the word Dominion was conferred as the country's title. By the 1950s, the term Dominion of Canada was no longer used by the United Kingdom, which considered Canada a "Realm of the Commonwealth"; the government of Louis St. Laurent ended the practice of using'Dominion' in the Statutes of Canada in 1951. In 1982, the passage of the Canada Act, bringing the Constitution of Canada under Canadian control, referred only to Canada, that year the name of the national holiday was changed from Dominion Day to Canada Day.
The term Dominion was used to distinguish the federal government from the provinces, though after the Second World War the term federal had replaced dominion. Indigenous peoples in present-day Canada include the First Nations, Métis, the last being a mixed-blood people who originated in the mid-17th century when First Nations and Inuit people married European settlers; the term "Aboriginal" as a collective noun is a specific term of art used in some legal documents, including the Constitution Act 1982. The first inhabitants of North America are hypothesized to have migrated from Siberia by way of the Bering land bridge and arrived at least 14,000 years ago; the Paleo-Indian archeological sites at Old Crow Flats and Bluefish Caves are two of the oldest sites of human habitation in Canada. The characteristics of Canadian indigenous societies included permanent settlements, complex societal hierarchies, trading networks; some of these cultures had collapsed by the time European explorers arrived in the late 15th and early 16th centuries and have only been discovered through archeological investigations.
The indigenous population at the time of the first European settlements is estimated to have been between 200,000
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl
Transport or transportation is the movement of humans and goods from one location to another. In other words the action of transport is defined as a particular movement of an organism or thing from a point A to the Point B. Modes of transport include air, water, cable and space; the field can be divided into infrastructure and operations. Transport is important because it enables trade between people, essential for the development of civilizations. Transport infrastructure consists of the fixed installations, including roads, airways, waterways and pipelines and terminals such as airports, railway stations, bus stations, trucking terminals, refueling depots and seaports. Terminals may be used both for maintenance. Vehicles traveling on these networks may include automobiles, buses, trucks, watercraft and aircraft. Operations deal with the way the vehicles are operated, the procedures set for this purpose, including financing and policies. In the transport industry and ownership of infrastructure can be either public or private, depending on the country and mode.
Passenger transport may be public. Freight transport has become focused on containerization, although bulk transport is used for large volumes of durable items. Transport plays an important part in economic growth and globalization, but most types cause air pollution and use large amounts of land. While it is subsidized by governments, good planning of transport is essential to make traffic flow and restrain urban sprawl. Humans' first means of transport involved walking and swimming; the domestication of animals introduced a new way to lay the burden of transport on more powerful creatures, allowing the hauling of heavier loads, or humans riding animals for greater speed and duration. Inventions such as the wheel and the sled helped make animal transport more efficient through the introduction of vehicles. Water transport, including rowed and sailed vessels, dates back to time immemorial, was the only efficient way to transport large quantities or over large distances prior to the Industrial Revolution.
The first forms of road transport involved animals, such as horses, oxen or humans carrying goods over dirt tracks that followed game trails. Many early civilizations, including those in Mesopotamia and the Indus Valley, constructed paved roads. In classical antiquity, the Persian and Roman empires built stone-paved roads to allow armies to travel quickly. Deep roadbeds of crushed stone underneath kept such roads dry; the medieval Caliphate built tar-paved roads. The first watercraft were canoes cut out from tree trunks. Early water transport was accomplished with ships that were either rowed or used the wind for propulsion, or a combination of the two; the importance of water has led to most cities that grew up as sites for trading being located on rivers or on the sea-shore at the intersection of two bodies of water. Until the Industrial Revolution, transport remained slow and costly, production and consumption gravitated as close to each other as feasible; the Industrial Revolution in the 19th century saw a number of inventions fundamentally change transport.
With telegraphy, communication became independent of the transport of physical objects. The invention of the steam engine followed by its application in rail transport, made land transport independent of human or animal muscles. Both speed and capacity increased allowing specialization through manufacturing being located independently of natural resources; the 19th century saw the development of the steam ship, which sped up global transport. With the development of the combustion engine and the automobile around 1900, road transport became more competitive again, mechanical private transport originated; the first "modern" highways were constructed during the 19th century with macadam. Tarmac and concrete became the dominant paving materials. In 1903 the Wright brothers demonstrated the first successful controllable airplane, after World War I aircraft became a fast way to transport people and express goods over long distances. After World War II the automobile and airlines took higher shares of transport, reducing rail and water to freight and short-haul passenger services.
Scientific spaceflight began in the 1950s, with rapid growth until the 1970s, when interest dwindled. In the 1950s the introduction of containerization gave massive efficiency gains in freight transport, fostering globalization. International air travel became much more accessible in the 1960s with the commercialization of the jet engine. Along with the growth in automobiles and motorways and water transport declined in relative importance. After the introduction of the Shinkansen in Japan in 1964, high-speed rail in Asia and Europe started attracting passengers on long-haul routes away from the airlines. Early in U. S. history, private joint-stock corporations owned most aqueducts, canals, railroads and tunnels. Most such transport infrastructure came under government control in the late 19th and early 20th centuries, culminating in the nationalization of inter-city passenger rail-service with the establishment of Amtrak. However, a movement to privatize roads and other infrastructure has gained some ground and adherents.
A mode of transport is a solution that makes use of a particular type of vehicle and operation. The transport of a person or of cargo may invol
Borders are geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states, other subnational entities. Borders are established through agreements between political or social entities that control those areas; some borders—such as a state's internal administrative border, or inter-state borders within the Schengen Area—are open and unguarded. Other borders are or controlled, may be crossed only at designated border checkpoints and border zones may be controlled. Borders may foster the setting up of buffer zones. A difference has been established in academic scholarship between border and frontier, the latter denoting a state of mind rather than state boundaries. In the past, many borders were not defined lines. Special cases in modern times were the Saudi Arabian–Iraqi neutral zone from 1922 to 1981 and the Saudi–Kuwaiti neutral zone from 1922 until 1970. In modern times, marchlands have been replaced by defined and demarcated borders.
For the purposes of border control and seaports are classed as borders. Most countries have some form of border control to regulate or limit the movement of people and goods into and out of the country. Under international law, each country is permitted to legislate the conditions that have to be met in order to cross its borders, to prevent people from crossing its borders in violation of those laws; some borders require presentation of legal paperwork like passports and visas, or other identity documents, for persons to cross borders. To stay or work within a country's borders aliens may need special immigration documents or permits. Moving goods across a border requires the payment of excise tax collected by customs officials. Animals moving across borders may need to go into quarantine to prevent the spread of exotic infectious diseases. Most countries prohibit carrying endangered animals across their borders. Moving goods, animals, or people illegally across a border, without declaring them or seeking permission, or deliberately evading official inspection, constitutes smuggling.
Controls on car liability insurance validity and other formalities may take place. In places where smuggling and infiltration are a problem, many countries fortify borders with fences and barriers, institute formal border control procedures; these can extend inland, as in the United States where the U. S. Customs and Border Protection service has jurisdiction to operate up to 100 miles from any land or sea boundary. On the other hand, some borders are signposted; this is common in countries within the European Schengen Area and on rural sections of the Canada–United States border. Borders may be unmarked in remote or forested regions. Migration within territorial borders, outside of them, represented an old and established pattern of movement in African countries, in seeking work and food, to maintain ties with kin who had moved across the porous borders of their homelands; when the colonial frontiers were drawn, Western countries attempted to obtain a monopoly on the recruitment of labor in many African countries, which altered the practical and institutional context in which the old migration patterns had been followed, some might argue, are still followed today.
The frontiers were porous for the physical movement of migrants, people living in borderlands maintained transnational cultural and social networks. A border may have been: Agreed by the countries on both sides Imposed by the country on one side Imposed by third parties, e.g. an international conference Inherited from a former state, colonial power or aristocratic territory Inherited from a former internal border, such as within the former Soviet Union Never formally defined. In addition, a border may be a de facto military ceasefire line. Political borders are imposed on the world through human agency; that means that although a political border may follow a river or mountain range, such a feature does not automatically define the political border though it may be a major physical barrier to crossing. Political borders are classified by whether or not they follow conspicuous physical features on the earth. Natural borders are geographical features that present natural obstacles to communication and transport.
Existing political borders are a formalization of such historical, natural obstacles. Some geographical features that constitute natural borders are: Oceans: oceans create costly natural borders. Few countries span more than one continent. Only large and resource-rich states are able to sustain the costs of governance across oceans for longer periods of time. Rivers: some political borders have been formalized along natural borders formed by rivers; some examples are: the Niagara River, the Rio Grande, the Rhine, the Mekong. If a precise line is desired, it is drawn along the thalweg, the deepest line along the river. In the Hebrew Bible, Moses defined the middle of the river Arnon as the border between Moab and the Israelite tribes settling east of the Jordan; the United States Supreme Court ruled in 1910 that the boundary between the American states of Maryland and West Virginia is the south bank of the Potoma
An ecoregion is an ecologically and geographically defined area, smaller than a bioregion, which in turn is smaller than an ecozone. All three of these are either greater than an ecosystem. Ecoregions cover large areas of land or water, contain characteristic, geographically distinct assemblages of natural communities and species; the biodiversity of flora and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are large areas of land or water where the probability of encountering different species and communities at any given point remains constant, within an acceptable range of variation. Three caveats are appropriate for all bio-geographic mapping approaches. Firstly, no single bio-geographic framework is optimal for all taxa. Ecoregions reflect the best compromise for as many taxa as possible. Secondly, ecoregion boundaries form abrupt edges. Thirdly, most ecoregions contain habitats. Biogeographic provinces may originate due to various barriers.
Some physical, some climatic and some ocean chemical related. The history of the term is somewhat vague, it had been used in many contexts: forest classifications, biome classifications, biogeographic classifications, etc; the concept of ecoregion of Bailey gives more importance to ecological criteria, while the WWF concept gives more importance to biogeography, that is, distribution of distinct biotas. An ecoregion is a "recurring pattern of ecosystems associated with characteristic combinations of soil and landform that characterise that region". Omernik elaborates on this by defining ecoregions as: "areas within which there is spatial coincidence in characteristics of geographical phenomena associated with differences in the quality and integrity of ecosystems". "Characteristics of geographical phenomena" may include geology, vegetation, hydrology and aquatic fauna, soils, may or may not include the impacts of human activity. There is significant, but not absolute, spatial correlation among these characteristics, making the delineation of ecoregions an imperfect science.
Another complication is that environmental conditions across an ecoregion boundary may change gradually, e.g. the prairie-forest transition in the midwestern United States, making it difficult to identify an exact dividing boundary. Such transition zones are called ecotones. Ecoregions can be categorized using an algorithmic approach or a holistic, "weight-of-evidence" approach where the importance of various factors may vary. An example of the algorithmic approach is Robert Bailey's work for the U. S. Forest Service, which uses a hierarchical classification that first divides land areas into large regions based on climatic factors, subdivides these regions, based first on dominant potential vegetation, by geomorphology and soil characteristics; the weight-of-evidence approach is exemplified by James Omernik's work for the United States Environmental Protection Agency, subsequently adopted for North America by the Commission for Environmental Cooperation. The intended purpose of ecoregion delineation may affect the method used.
For example, the WWF ecoregions were developed to aid in biodiversity conservation planning, place a greater emphasis than the Omernik or Bailey systems on floral and faunal differences between regions. The WWF classification defines an ecoregion as: A large area of land or water that contains a geographically distinct assemblage of natural communities that: Share a large majority of their species and ecological dynamics. According to WWF, the boundaries of an ecoregion approximate the original extent of the natural communities prior to any major recent disruptions or changes. WWF has identified 867 terrestrial ecoregions, 450 freshwater ecoregions across the Earth; the use of the term ecoregion is an outgrowth of a surge of interest in ecosystems and their functioning. In particular, there is awareness of issues relating to spatial scale in the study and management of landscapes, it is recognized that interlinked ecosystems combine to form a whole, "greater than the sum of its parts". There are many attempts to respond to ecosystems in an integrated way to achieve "multi-functional" landscapes, various interest groups from agricultural researchers to conservationists are using the "ecoregion" as a unit of analysis.
The "Global 200" is the list of ecoregions identified by WWF as priorities for conservation. Ecologically based movements like bioregionalism maintain that ecoregions, rather than arbitrarily defined political boundaries, provide a better foundation for the formation and governance of human communities, have proposed ecoregions and watersheds as the basis for bioregional democracy initiatives. Terrestrial ecoregions are land ecoregions, as distinct from marine ecoregions. In this context, terrestrial is used to mean "of land", rather than the more general sense "of Earth". WWF ecologists divide the land surface of the Earth into 8 major ecozones containing 867 smaller terrestrial ecoregions; the WWF effort is a synthesis of