User:Canhelp/sandbox/Invasive species
Organism occurring in a new habitat / From Wikipedia, the free encyclopedia
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An invasive species is a nonindigenous species that spreads from the point of introduction and becomes abundant.[2]
The invasive species label attaches only to populations of species whose impact upon introduction has altered their new environment.[3] Although this impact can be beneficial, the term as most often used applies to introduced species that affect the invaded habitats and bioregions adversely, causing ecological, environmental, or economic damage.[4] This includes plant species labeled as "exotic pest plants" and "invasive exotics" growing in native plant communities.[5][6][7] The term is also used by land managers, botanists, researchers, horticulturalists, conservationists, and the public for noxious weeds.[8]
The term "invasive" is poorly defined and often very subjective,[9] and some broaden the term to include indigenous or "native" species that have colonized natural areas[9] – for example deer considered by some to be overpopulating their native zones and adjacent suburban gardens in the Northeastern and Pacific Coast regions of the United States.[10] The definition of "native" is also sometimes controversial. For example, the ancestors of Equus ferus (modern horses) evolved in North America and radiated to Eurasia before becoming locally extinct. Upon returning to North America in 1493 during their human-assisted migration, it is debatable as to whether they were native or exotic to the continent of their evolutionary ancestors.[11]
Invasion of long-established ecosystems by organisms is a natural phenomenon, but human-facilitated introductions have increased massively the rate, scale, and geographic range of invasion. For millenia, humans have served as both accidental and deliberate dispersal agents, beginning with our earliest migrations, accelerating in the age of discovery, and accelerating again with international trade.[12][13] Notable examples of invasive plant species include the kudzu vine, Andean pampas grass, and yellow starthistle. Animal examples include the New Zealand mud snail, feral pigs, European rabbits, grey squirrels, domestic cats, carp and ferrets.[14][15][16] Some popular reference sources now name Homo sapiens, especially modern-age humans, as an invasive species,[17][18] but broad appreciation of human learning capacity and our behavioral potential and plasticity argues against any such fixed categorization.[19][20]