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==Human influence on extinction==
==Human influence on extinction==
Extinction of animals and plants caused by human actions may go as far back as the late [[Pleistocene]], over 12,000 years BP, but there is no direct evidence for this theory and it is more likely abrupt climate change played a much higher role in the extinction of larger mammals.<ref name=Zalasiewicz>{{cite journal|last=Zalasiewicz|first=Jan|coauthors=Williams, Mark; Smith, Alan; Barry, Tiffany L.; Coe, Angela L.; Bown, Paul R.; Brenchley, Patrick; Cantrill, David; Gale, Andrew; Gibbard, Philip; Gregory, F. John; Hounslow, Mark W.; Kerr, Andrew C.; Pearson, Paul; Knox, Robert; Powell, John; Waters, Colin; Marshall, John; Oates, Michael; Rawson, Peter; Stone, Philip|title=Are we now living in the Anthropocene|journal=GSA Today|year=2008|volume=18|issue=2|pages=4|doi=10.1130/GSAT01802A.1}}</ref> Extinctions that are due to human activity ([[human impact on the environment|anthropogenic]]), particularly hypothesized future events, have also been labelled the ''anthropocene extinction''.<ref name="wooldridge2008">{{cite journal|doi=10.5194/bgd-5-2401-2008|last=Wooldridge|first=S. A.|date=9 June 2008|title=Mass extinctions past and present: a unifying hypothesis|journal=Biogeosciences Discuss|publisher=Copernicus|volume=5|pages=2401–2423|url=http://www.biogeosciences-discuss.net/5/2401/2008/bgd-5-2401-2008.html|issue=3}}</ref><ref name="jackson2008">{{cite doi|10.1073/pnas.0802812105}}</ref> The [[Anthropocene]] is a term introduced in 2000.
Extinction of animals and plants caused by human actions may go as far back as the late [[Pleistocene]], over 12,000 years BP, but there is no direct evidence for this theory and it is more likely that abrupt climate change (which itself was perhaps human-caused) played a much higher role in the extinction of larger mammals.<ref name=Zalasiewicz>{{cite journal|last=Zalasiewicz|first=Jan|coauthors=Williams, Mark; Smith, Alan; Barry, Tiffany L.; Coe, Angela L.; Bown, Paul R.; Brenchley, Patrick; Cantrill, David; Gale, Andrew; Gibbard, Philip; Gregory, F. John; Hounslow, Mark W.; Kerr, Andrew C.; Pearson, Paul; Knox, Robert; Powell, John; Waters, Colin; Marshall, John; Oates, Michael; Rawson, Peter; Stone, Philip|title=Are we now living in the Anthropocene|journal=GSA Today|year=2008|volume=18|issue=2|pages=4|doi=10.1130/GSAT01802A.1}}</ref> While previous mass extinctions were due to natural environmental causes, research shows that wherever on Earth humans have migrated other species have become extinct. Human overpopulation especially in the past two centuries is said to be the underlying cause of the Sixth Extinction. At present, the rate of extinction of species is estimated 100 to 1000 times higher than the "base" or middle rate of extinction regarding the natural evolution of the planet<ref>{{cite journal|author=Lawton, J. H. and May, R. M.|work=Extinction Rates|journal=Journal of Evolutionary Biology|publisher=Oxford University Press|location=Oxford|year=1995}}</ref> and also the current rate of extinction is, therefore, 10 to 100 times higher than any of the previous mass extinctions in the history of Earth. On the other hand, this extinction concerns a large number of plants, different from previous extinctions.
Extinctions that are due to human activity ([[human impact on the environment|anthropogenic]]), particularly hypothesized future events, have also been labelled the ''anthropocene extinction''.<ref name="wooldridge2008">{{cite journal|doi=10.5194/bgd-5-2401-2008|last=Wooldridge|first=S. A.|date=9 June 2008|title=Mass extinctions past and present: a unifying hypothesis|journal=Biogeosciences Discuss|publisher=Copernicus|volume=5|pages=2401–2423|url=http://www.biogeosciences-discuss.net/5/2401/2008/bgd-5-2401-2008.html|issue=3}}</ref><ref name="jackson2008">{{cite doi|10.1073/pnas.0802812105}}</ref> The [[Anthropocene]] is a term introduced in 2000.


Recent extinctions described are well-documented,<ref name="Zalasiewicz"/> but the [[nomenclature]] used varies. The term [[Anthropocene]] is a term that is used by few scientists,<ref name=Zalasiewicz /> and some commentators may refer to the current and projected future extinctions as part of a longer Holocene extinction.<ref>{{cite book|last=Elewa|first=Ashraf M. T|editor-first=Ashraf M. T |editor-last=Elewa |title=Mass Extinction|pages=191–194|chapter=14. Current mass extinction|doi=10.1007/978-3-540-75916-4_14}}</ref> The Holocene–Anthropocene boundary is contested, with some commentators asserting significant human influence on climate for much of what is normally regarded as the [[Holocene]] [[Epoch (geology)|Epoch]].<ref>{{cite journal | doi = 10.1038/news031208-7 | first1= Betsy |last1= Mason | title = Man has been changing climate for 8,000 years | journal = Nature | date = 10 December 2003 }}</ref> Other commentators place the Holocene–Anthropocene boundary at the [[industrial revolution]] while also saying that "Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. "<ref name=Zalasiewicz />
Recent extinctions described are well-documented,<ref name="Zalasiewicz"/> but the [[nomenclature]] used varies. The term [[Anthropocene]] is a term that is used by few scientists,<ref name=Zalasiewicz /> and some commentators may refer to the current and projected future extinctions as part of a longer Holocene extinction.<ref>{{cite book|last=Elewa|first=Ashraf M. T|editor-first=Ashraf M. T |editor-last=Elewa |title=Mass Extinction|pages=191–194|chapter=14. Current mass extinction|doi=10.1007/978-3-540-75916-4_14}}</ref> The Holocene–Anthropocene boundary is contested, with some commentators asserting significant human influence on climate for much of what is normally regarded as the [[Holocene]] [[Epoch (geology)|Epoch]].<ref>{{cite journal | doi = 10.1038/news031208-7 | first1= Betsy |last1= Mason | title = Man has been changing climate for 8,000 years | journal = Nature | date = 10 December 2003 }}</ref> Other commentators place the Holocene–Anthropocene boundary at the [[industrial revolution]] while also saying that "Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. "<ref name=Zalasiewicz />

Revision as of 17:04, 16 February 2013

The dodo, a flightless bird of Mauritius, became extinct during the mid-late seventeenth century after humans destroyed the forests where the birds made their homes and introduced mammals that ate their eggs.

The Holocene extinction is the extinction of species during the present Holocene epoch (since around 10,000 BC). The large number of extinctions span numerous families of plants and animals including mammals, birds, amphibians, reptiles and arthropods. Although 875 extinctions occurring between 1500 and 2009 have been documented by the International Union for Conservation of Nature and Natural Resources,[1] the vast majority are undocumented. According to the species-area theory and based on upper-bound estimating, up to 140,000 species per year may be the present rate of extinction.[2]

The Holocene extinction includes the disappearance of large mammals known as megafauna, starting between 9,000 and 13,000 years ago, the end of the last Ice Age. Such disappearances are considered to be results of both climate change and the proliferation of modern humans. These extinctions, occurring near the Pleistocene–Holocene boundary, are sometimes referred to as the Quaternary extinction event or Ice Age extinction. The Holocene extinction continues into the 21st century.

There is no general agreement on whether to consider more recent extinctions as a distinct event, merely part of the Quaternary extinction event, or just a result of natural evolution on a non-geologic scale of time. Only during these most recent parts of the extinction have plants also suffered large losses. Overall, the Holocene extinction can be characterized by humanity's presence.

Prehistoric extinctions

See also: Megafaunal mass extinctions

North and South America

There was a debate as to the extent to which the disappearance of megafauna at the end of the last glacial period can be attributed to human activities, directly, by hunting, or indirectly, by decimation of prey populations. Recent discoveries at Monte Verde in South America, and at Meadowcroft Rock Shelter in Pennsylvania have effectively ended the "clovis first" position of American Archaeology and pushed the arrival of humans in the Americas back many thousands of years. This coupled with a more complete fossil record of the extinct animals has weakened the correlation between human occupation and mega-fauna extinction in the Americas. However around the world there is often a very strong correlation between human arrival and mega-fauna extinction, an example being Wrangle Island in Siberia, where the extinction of Mammoths (approximately 2000 bce) coincided directly with the arrival of humans. Further more, the success of mega-fauna in surviving previous more severe periods of climate change suggest natural events were not entirely to blame.

The ongoing extinction seems more outstanding in light of separating recent extinctions (approximately since the industrial revolution) from the Pleistocene extinction near the end of the last glacial period. The latter is exemplified by the extinction of large herbivores such as the woolly mammoth and the carnivores that preyed on them. Therefore, the logical basis for the theory may be flawed, since it presumes that early Americans, despite being only a slight fraction of the population of industrial era America and armed with rudimentary tools, were many times more destructive than later historic humans who engaged in the often deliberate eradication of species. However it should be considered that the ecosystems encountered by the first Americans had not been exposed to human interaction and were far less resilient to man made changes than the ecosystems encountered by industrial era humans, those environments seasoned as they were, having been exposed to over 10,000 years of human interaction. Therefore the actions of the Clovis people and likewise, despite seeming insignificant by today's standards could indeed have had a profound effect on the ecosystems and wild life which was entirely unused to human influence.

New Zealand

c. 1500, several species became extinct after Polynesian settlers arrived, including:

Pacific, including Hawaii

Recent research, based on archaeological and paleontological digs on 70 different islands, has shown that numerous species went extinct as people moved across the Pacific, starting 30,000 years ago in the Bismarck Archipelago and Solomon Islands.[3] It is currently estimated that among the bird species of the Pacific some 2000 species have gone extinct since the arrival of humans.[4] Among the extinctions were:

Ten species or subspecies of birds have disappeared from the Hawaiian islands since the 1980s. These include the Kaua'i O'o, Nukupu'u, 'Akialoa, Kama'o, Po'ouli, and others.

Madagascar

Starting with the arrival of humans around 2000 years ago, nearly all of the island's megafauna became extinct, including:

Indian Ocean Islands

Starting c. 1500, a number of species became extinct upon human settlement of the islands, including:

Ongoing Holocene extinction

One scientist estimates the extinction may be 10,000 times the background extinction rate (the average between mass extinction events).[5][6] Nevertheless most scientists predict a much lower extinction rate than this outlying estimate.[7] Stuart Pimm stated "the current rate of species extinction is about 100 times the natural rate" for plants.[8]

Megafaunal extinctions continue into the 21st century. Modern extinctions are more directly attributable to human influences. Extinction rates are minimized in the popular imagination by the survival of captive populations of animals that are extinct in the wild (Père David's Deer, etc.), by marginal survivals of highly publicized megafauna that are ecologically extinct (the Giant Panda, Sumatran Rhinoceros, North American Black-Footed Ferret, etc.) and by extinctions among arthropods. Some examples of modern extinctions of "charismatic" mammal fauna include:

Many birds have become extinct as a result of human activity, especially birds endemic to islands, including many flightless birds (see a more complete list under extinct birds). Notable extinct birds include:

A 1998 poll conducted by the American Museum of Natural History found that seventy percent of biologists believe that we are in the midst of an anthropogenic extinction.[10] Numerous scientific studies—such as a 2004 report published in Nature,[11] and papers authored by the 10,000 scientists who contribute to the IUCN's annual Red List of threatened species—have since reinforced this conviction. In The Future of Life (2002), E.O. Wilson of Harvard calculated that, if the current rate of human disruption of the biosphere continues, one-half of Earth's higher lifeforms will be extinct by 2100.

Peter Raven, past President of the American Association for the Advancement of Science (AAAS), states in the foreword to their publication AAAS Atlas of Population and Environment:[12] "We have driven the rate of biological extinction, the permanent loss of species, up several hundred times beyond its historical levels, and are threatened with the loss of a majority of all species by the end of the 21st century."[13] Some of the human causes of the current extinctions include deforestation, hunting, pollution, climate change,[14] and the introduction of non-native species.

The Golden Toad of Costa Rica, extinct since around 1989. Its disappearance has been attributed to a confluence of several factors, including El Niño warming, fungus, and the introduction of invasive species.

189 countries which are signatory to the Convention on Biological Diversity (Rio Accord) have committed to preparing a Biodiversity Action Plan, a first step at identifying specific endangered species and habitats, country by country.

Various species are predicted to go extinct in the near future.[15][16][17][18]

Human influence on extinction

Extinction of animals and plants caused by human actions may go as far back as the late Pleistocene, over 12,000 years BP, but there is no direct evidence for this theory and it is more likely that abrupt climate change (which itself was perhaps human-caused) played a much higher role in the extinction of larger mammals.[19] While previous mass extinctions were due to natural environmental causes, research shows that wherever on Earth humans have migrated other species have become extinct. Human overpopulation especially in the past two centuries is said to be the underlying cause of the Sixth Extinction. At present, the rate of extinction of species is estimated 100 to 1000 times higher than the "base" or middle rate of extinction regarding the natural evolution of the planet[20] and also the current rate of extinction is, therefore, 10 to 100 times higher than any of the previous mass extinctions in the history of Earth. On the other hand, this extinction concerns a large number of plants, different from previous extinctions.

Extinctions that are due to human activity (anthropogenic), particularly hypothesized future events, have also been labelled the anthropocene extinction.[21][22] The Anthropocene is a term introduced in 2000.

Recent extinctions described are well-documented,[19] but the nomenclature used varies. The term Anthropocene is a term that is used by few scientists,[19] and some commentators may refer to the current and projected future extinctions as part of a longer Holocene extinction.[23] The Holocene–Anthropocene boundary is contested, with some commentators asserting significant human influence on climate for much of what is normally regarded as the Holocene Epoch.[24] Other commentators place the Holocene–Anthropocene boundary at the industrial revolution while also saying that "Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. "[19]

Three hypotheses have been proposed to explain the extinction of megafauna in the late Pleistocene. Of these, only two have much scientific credibility. Although Ross McPhee proposed that a hyper-disease may have been the cause of the extinction,[25] the study by Lyons et al., demonstrated conclusively that a hyperdisease was unlikely to have caused the extinction.[26] The two main theories to the extinction are climate change and human hunting. The climate change theory has suggested that a change in climate near the end of the late Pleistocene stressed the megafauna to the point of extinction.[27] Most scientists favor abrupt climate change as the catalyst for the extinction of the mega-fauna at the end of the Pleistocene, but there are many who believe increased hunting from early modern humans also played a part.[28][29]

See also

References

  1. ^ "Extinction continues apace". International Union for Conservation of Nature. 03 November 2009. Retrieved 18 October 2012. {{cite web}}: Check date values in: |date= (help)
  2. ^ S.L. Pimm, G.J. Russell, J.L. Gittleman and T.M. Brooks, The Future of Biodiversity, Science 269: 347–350 (1995)
  3. ^ Steadman & Martin 2003
  4. ^ Steadman 1995
  5. ^ Wilson, Edward O. (2003). The Future of life (1st Vintage Books ed. ed.). New York: Vintage Books. ISBN 9780679768111. {{cite book}}: |edition= has extra text (help)
  6. ^ C.Michael Hogan. 2010. Edenic Period. Encyclopedia of Earth. National Council for Science and Environment. ed. Galal Hassan, ed in chief Cutler Cleveland, Washington DC
  7. ^ J.H.Lawton and R.M.May, Extinction Rates, Oxford University Press, Oxford, UK
  8. ^ Has Plant Life Reached Its Limits? September 20, 2012
  9. ^ Rubinkam, Michael (02 March 2011). "Federal researchers declare eastern cougar extinct". Salon.com. Retrieved 18 October 2012. {{cite news}}: Check date values in: |date= (help)
  10. ^ American Museum of Natural History Press Release
  11. ^ Study sees mass extinctions via warming. MSNBC. URL accessed July 26, 2006.
  12. ^ "Atlas of Population and Environment". AAAS. 2000. Retrieved 2008-02-12.
  13. ^ "Atlas of Population and Environment, Foreword". American Association for the Advancement of Science (AAAS). 2000. Retrieved 2008-02-12.
  14. ^ "Measuring extinction, species by species". The Economic Times. 2008-11-06. Retrieved 2010-05-20.
  15. ^ Lions, tigers, big cats may face extinction in 20 years by Dan Vergano, USA Today
  16. ^ Exotic animals: 18 tiger deaths a cruel blow to imperiled species October 20, 2011 LA Times
  17. ^ Jaguars cling to survival in Argentina's forests by Kylie Stott Tue Oct 11, 2011 Reuters
  18. ^ Poachers Drive Javan Rhino to Extinction in Vietnam by John R. Platt October 25, 2011 Scientific American
  19. ^ a b c d Zalasiewicz, Jan (2008). "Are we now living in the Anthropocene". GSA Today. 18 (2): 4. doi:10.1130/GSAT01802A.1. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  20. ^ Lawton, J. H. and May, R. M. (1995). Journal of Evolutionary Biology. Oxford: Oxford University Press. {{cite journal}}: Missing or empty |title= (help); More than one of |work= and |journal= specified (help)CS1 maint: multiple names: authors list (link)
  21. ^ Wooldridge, S. A. (9 June 2008). "Mass extinctions past and present: a unifying hypothesis". Biogeosciences Discuss. 5 (3). Copernicus: 2401–2423. doi:10.5194/bgd-5-2401-2008.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  22. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1073/pnas.0802812105, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1073/pnas.0802812105 instead.
  23. ^ Elewa, Ashraf M. T. "14. Current mass extinction". In Elewa, Ashraf M. T (ed.). Mass Extinction. pp. 191–194. doi:10.1007/978-3-540-75916-4_14.
  24. ^ Mason, Betsy (10 December 2003). "Man has been changing climate for 8,000 years". Nature. doi:10.1038/news031208-7.
  25. ^ MacPhee and Marx published their hyperdisease hypothesis in 1997. "The 40,000-year plague: Humans, hyperdisease, and first-contact extinctions." In S. M. Goodman and B. D. Patterson (eds), Natural Change and Human Impact in Madagascar, pp 169-217, Smithsonian Institution Press: Washington DC.
  26. ^ Lyons, S. Kathleen (2004). "Was a 'hyperdisease' responsible for the late Pleistocene megafaunal extinction?". Ecology Letters. 7 (9): 859–868. doi:10.1111/j.1461-0248.2004.00643.x. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  27. ^ Graham, R. W. and Mead, J. I. 1987. Environmental fluctuations and evolution of mammalian faunas during the last deglaciation in North America. In: Ruddiman, W. F. and H.E. Wright, J., editors. North America and Adjacent Oceans During the Last Deglaciation. Volume K-3. The Geology of North America, Geological Society of America
  28. ^ Martin P. S. (1967). Prehistoric overkill. In Pleistocene extinctions: The search for a cause (ed. P.S. Martin and H.E. Wright). New Haven: Yale University Press. ISBN 0-300-00755-8.
  29. ^ "Of mice, mastodons and men: human-mediated extinctions on four continents" (PDF). Evolutionary Ecology Research. 6: 339–358. 2004. Retrieved 18 October 2012. {{cite journal}}: Unknown parameter |authors= ignored (help)

Further reading


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