Holocene extinction

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 refers to 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, 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.

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 climate change or the proliferation of modern humans, or both. 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 climate change and humanity's presence.

In research published in the Proceedings of the National Academy of Sciences the Lead author Larry Gorenflo from Penn State University stated "Biologists estimate annual loss of species at 1,000 times or more greater than historic rates, and linguists predict that 50-90% of the world's languages will disappear by the end of the century," claiming that there is a link between the loss of biodiversity and the disappearance of endangered languages and cultures.

Findings show the rate of what is called the sixth extinction event, the fifth being the Cretaceous–Paleogene extinction event, is accelerating.

The prehistoric extinction events

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 demonstrates that there is no longer any correlation between human occupation and mega-fauna extinction in the Americas.

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 is deeply 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.

Younger extinctions

Main articles: Oldest Dryas, Older Dryas, and Younger Dryas

New Zealand

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

• Ten species of Moa, giant flightless ratite birds.
• The giant Haast's Eagle, Harpagornis
• The flightless predatory Adzebills.

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 (Steadman & Martin 2003). It is currently estimated that among the bird species of the Pacific some 2000 species have gone extinct since the arrival of humans (Steadman 1995). Among the extinctions were:

• The Moa-nalos, grazing ducks from Hawaii.
• The Nēnē-nui, or Woodwalking Goose, an extinct species of goose that once inhabited Maui.
• A giant megapode from New Caledonia.
• Mekosuchine crocodiles from New Caledonia, Fiji and Samoa.

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:

• Eight or more species of elephant birds, giant flightless ratites in the genera Aepyornis and Mullerornis.
• 17 species of lemur, known as giant, subfossil lemurs, including:
  • Giant Aye-aye (Daubentonia robusta)
  • Sloth lemurs, including chimpanzee-sized Palaeopropithecus and gorilla-sized Archaeoindris
  • Koala lemurs (Megaladapis), a koala-like, orangutan-sized arboreal lemur
  • Monkey lemurs, most terrestrial of lemurs, often compared to baboons or macaques.
  • Pachylemur, a genus of giant ruffed lemurs
• Giant Fossa
• Plesiorycteropus, a genus containing two species of digging mammal unlike anything alive today
• Two species of Malagasy Hippopotamus

Indian Ocean Islands

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

• several species of giant tortoise on Seychelles and Mascarene Islands
• 14 species of birds on the Mascarene Islands, including the Dodo, the Rodrigues Solitaire, and the unrelated Réunion Solitaire.

Ongoing Holocene extinction

One scientist estimates the extinction may be 10,000 times the background extinction rate (the average between mass extinction events). Nevertheless, in earlier studies, most scientists predicted a much lower extinction rate than this outlying estimate.

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:

• Aurochs, Europe
• Tarpan, Europe
• Thylacine or Tasmanian Tiger, Thylacinus cynocephalus, Tasmania
• Quagga, a zebra subspecies, Southeast Africa
• Steller's Sea Cow
• Bluebuck
• Pyrenean Ibex
• Falkland Islands Wolf
• Atlas Bear
• Caribbean Monk Seal
• The closely related Bali Tiger and Javan Tiger
• Eastern Cougar
• Western Black Rhinoceros

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:

• the Dodo, the giant flightless pigeon of Mauritius, Indian Ocean
• the Great Auk of islands in the north Atlantic
• the Passenger Pigeon of North America
• several species of Moa, giant flightless birds from New Zealand
• the Carolina Parakeet of the American southeast

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. Numerous scientific studies—such as a 2004 report published in Nature, 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: "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." Some of the human causes of the current extinctions include deforestation, hunting, pollution, climate change, 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.

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

Recent extinctions described are well-documented, but the nomenclature used varies. The term Anthropocene is a term that is used by few scientists, and some commentators may refer to the current and projected future extinctions as part of a longer Holocene extinction. 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. 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. "

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, the study by Lyons et al., demonstrated conclusively that a hyperdisease was unlikely to have caused the extinction. 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. 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.

See also

• Ape extinction
• Biodiversity
• Effects of global warming
• Holocene extinctions (category)
• List of extinct animals
• List of extinct plants
• Timeline of extinctions

Further reading

• Kolbert, Elizabeth (2009). "The Sixth Extinction? There have been five great die-offs in history. This time, the cataclysm is us". The New Yorker. Retrieved May 2012. {{cite journal}}: Check date values in: |accessdate= (help); Unknown parameter |month= ignored (help)
• Leakey, Richard (1996). The Sixth Extinction: Patterns of Life and the Future of Humankind. New York: Anchor Books. ISBN 0-385-46809-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Martin, P. S. (1967). Pleistocene Extinctions: The Search for a Cause. New Haven: Yale University Press. ISBN 0-300-00755-8. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Ted Oakes (2003). Land of Lost Monsters: Man Against Beast--The Prehistoric Battle for the Planet. Hylas Publishing. ISBN 1-59258-005-X.
• Steadman, D. W. (1995). "Prehistoric extinctions of Pacific island birds: biodiversity meets zooarchaeology". Science. 267 (5201): 1123–1131. doi:10.1126/science.267.5201.1123. PMID 17789194. {{cite journal}}: Cite has empty unknown parameters: |month= and |coauthors= (help)
• Steadman, D. W. (2003). "The late Quaternary extinction and future resurrection of birds on Pacific islands" (– ^{Scholar search}). Earth Science Reviews. 61 (1–2): 133–147. Bibcode:2003ESRv...61..133S. doi:10.1016/S0012-8252(02)00116-2. {{cite journal}}: Cite has empty unknown parameter: |month= (help); External link in |format= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)

External links

• World facing 'extinction crisis' by Margaret Munro, Postmedia News October 27, 2010
• Species Selection Maintains Self-Incompatibility by Goldberg et al. Science 22 October 2010: 493-49
• The extinction risk for birds, mammals and amphibian by Ariel Zirulnick in The Christian Science Monitor
• 2010 may be the worst year ever for coral death in the Caribbean, Science 22 October 2010:Vol. 330. no. 6003, p. 437
• Early Warning for Endangered Species? by Erik Stokstad on 8 September 2010
• Climate Change Causing Lizards to 'Wink Out of Existence' by Michael Price on 13 May 2010 Science (journal)
• "NATIONAL SURVEY REVEALS BIODIVERSITY CRISIS - SCIENTIFIC EXPERTS BELIEVE WE ARE IN MIDST OF FASTEST MASS EXTINCTION IN EARTH'S HISTORY". Retrieved 2008-08-03.
• "An Interview with Dr. Peter Raven, director of the Missouri Botanical Garden". Retrieved 2008-08-03.
• "Mass Extinction underway". This web site, updated regularly, provides many hundreds of links to articles in scientific journals and major news media about the current anthropogenic mass extinction. Retrieved 2010-09-05.
• Firestone RB, West A, Kennett JP; et al. (2007). "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling". Proceedings of the National Academy of Sciences of the United States of America. 104 (41): 16016–21. doi:10.1073/pnas.0706977104. PMC 1994902. PMID 17901202. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)