Invasive Species

A invasive species or invading species is an exotic species which becomes an agent of disturbance Nuisible with the biodiversity indigenous of the natural ecosystem S natural or semi among which it was established. The phenomena of biological Invasion are regarded today by UNO as one of the great causes of regression of the Biodiversité, with the Pollution, the ecological Fragmentation of the ecosystems and hunting/fishing/overexploitation of certain species.

Qualifier of species invasive is associated with Species, with Subspecies or with entity of level taxonomic lower which is outside its surface of Répartition or of its surface of Dispersion potential (i.e. out of the geographical field that it occupies naturally or can occupy without human interventions by particular introduction or steps) and is applicable to very part of an individual (Gamète or Propagule) likely to survive and to reproduce

Actually, it would be necessary to speak about “ invasive population ” and not about invasive species.

Appearance of the concept

The concept of invasive species is a recent concept. To include/understand it, it should be known that balances between Espèce S within the ecosystem S, on human scale of time, relatively are at least well established. In the absence of human intervention, the phenomena of brutal extension of the surface of distribution of a species (known as invasive) are extremely rare. The man, since it developed the Chasse, the Agriculture and the breeding, and more still since it has average techniques allowing him to be present and to move quickly on all the continents, became a very important vector of displacement of species out of their ecosystems of origin, voluntarily or accidentally. Species become also spontaneously invasive because hunting made disappear their predator or that the man their offered a new medium easy to colonize for them (monospecific cultures and forests in particular). Sometimes they colonize simply the surface of distribution and the ecological niche of species which the man made disappear or weakened. Many introduced species were it involuntarily, the Ballastage and déballastage of the tradind ships, transport by the hulls of barges and of ships for example, is vectors of introduction of species which was initially ignored, then underestimated, and against which few measurements are taken. Some as Charles-François Boudouresque prefers speech of introduced species to mark this fact, but all the introduced species do not become naturalized species nor do not produce a biological Invasion. Some remain very dependant on the artificial conditions caused by the man.

The populations which are naturalized often escape human control but all are not invasive . It is estimated that approximately a species introduced on thousand becomes invasive, i.e. presents an ecological impact (cf definition) but this concept first of all was a anthropic concept parce these are the economic impacts or social serious that the human ones noticed initially.

See also: invading Plant

The role of long-distance transport

The invasive species introduced with water of ballast or under the ship hulls are increasingly numerous. The trains, trucks and cars transport from there too. And a study of 2007 of the university of Oxford showed that in areas with the comparable climate, more one approaches a zone served by air lines, more increases the risk of invasion by animal foreign species, with a “window of invasion” in June - August, a priori because of the number of flights and passengers which increases and favorable climatic conditions. 800 air lines were studied from May 1st, 2005 to April 30th, 2006 (either 3 million flights approximately).

Examples

The examples of invasive species having caused more or less important economic crises do not miss:
  • Mushroom Phytophtora infestans on the potato culture in Ireland causing the great famine in 1845
  • Phylloxéra Viteus vitifoliae on the European vines at the end of the 19th century
  • Jellyfish Mnemiopsis leidyi in Black Sea having weakened considerably the streaked fishing resource
  • Mussel which can stop drains, obstruct navigation and decrease the biodiversity
  • common Guêpe Vespula vulgaris in Australia and in New Zealand
  • without speaking about the older cases like the introduction of the black rat Rattus rattus and the gray rat Rattus norvegicus in Europe with the the Middle Ages
  • Scorpion in certain forests drômoises having deeply upset the ecosystem and which can appear dangerous for the man.
  • Homo sapiens can be regarded as an invasive species because of an uncontrolled demography, significant and harmful impacts on the total environment (flora, fauna, climates…),
--> In a context where human displacements are increasingly more numerous, the climatic impact of the human activities always more extremely and the temptation of recourse to the organizations genetically modified increasingly larger, the risk of an increase in the phenomena of invasive species with its consequences on the biodiversity is quite real. It started besides to be taken into account during the Conférence of Rio in 1992. They are today the second cause of regression of the biodiversity.

Examples of case of invasions by introduced species

See too

Random links:Joachim Camerarius the Young person | Edmond Charlot | Valley Park (Missouri) | In situ | Standardization and standardization of the orthography (Zaire) | Logiciel_de_MontaVista