In the natural course of events, species become extinct
for a number of reasons, including but not limited to, extinction
of a necessary host, prey or pollinator, inter-species competition,
inability to deal with evolving diseases and changing environmental
conditions (particularly sudden changes) which can act to
introduce novel predators, or to remove prey. Recently in
geologic time, humans have become an additional cause of
extinction (many people would say premature extinction)
for some species, either as a new mega-predator or by transporting
animals and plants from one part of the world to another.
The later has been occurring for thousands of years, sometimes
deliberately (e.g., livestock released by sailors onto islands
as a source of future food) and sometimes accidentally (e.g.,
rats escaping from boats). In most cases, such introductions
are unsuccessful, but when they do become established as
an invasive alien species, the consequences can be catastrophic.
Invasive alien species can affect native species directly
by eating them, competing with them, and introducing pathogens
or parasites that sicken or kill them or, indirectly, by
destroying or degrading their habitat. Human populations
may themselves act as invasive predators. According to the
"overkill hypothesis", the swift extinction of the megafauna
in areas such as Australia (40,000 years before present),
North and South America (12,000 years before present), Madagascar,
Hawaii (300-1000 CE), and New Zealand (1300-1500 CE), resulted
from the sudden introduction of human beings to environments
full of animals that had never seen them before, and were
therefore completely unadapted to their predation techniques.
Diamond, Jared (1999). "Up to the Starting Line".
Guns, Germs, and Steel. W. W. Norton. pp. 43–44. ISBN
Sahney, S., Benton, M.J. and Ferry, P.A. (2010).
"Links between global taxonomic diversity, ecological
diversity and the expansion of vertebrates on land"
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Newman, Mark. "A Mathematical Model for Mass Extinction".
Cornell University. May 20, 1994. Retrieved July 30,
Raup, David M. Extinction: Bad Genes or Bad Luck?
W.W. Norton and Company. New York. 1991. pp. 3–6, ISBN
Species disappearing at an alarming rate, report
says. MSNBC. Retrieved July 26, 2006.
Wilson, E.O., The Future of Life (2002) (ISBN 0-679-76811-4).
See also: Leakey, Richard, The Sixth Extinction : Patterns
of Life and the Future of Humankind, ISBN 0-385-46809-1
Davis, Paul and Kenrick, Paul. Fossil Plants. Smithsonian
Books, Washington D.C. (2004). Morran, Robin, C.; A
Natural History of Ferns. Timber Press (2004). ISBN
See: Niles Eldredge, Time Frames: Rethinking of Darwinian
Evolution and the Theory of Punctuated Equilibria, 1986,
Heinemann ISBN 0-434-22610-6
Maas, Peter. "Extinct in the Wild" The Extinction
Website. URL accessed January 26 2007.
Quince, C. et al. (PDF). Deleting species from model
food webs. Archived from the original on 2006-09-25.
Stearns, Beverly Peterson and Stephen C. (2000).
"Preface". Watching, from the Edge of Extinction. Yale
University Press. pp. x. ISBN 0-300-08469-2.
"Population Bomb Author's Fix For Next Extinction:
Educate Women". Scientific American. August 12, 2008.
"2004 Red List". IUCN Red List of Threatened Species.
World Conservation Union. Archived from the original
on 12 February 2008. Retrieved September 20, 2006.
Payne, J.L. & S. Finnegan (2007). "The effect of
geographic range on extinction risk during background
and mass extinction". Proc. Nat. Acad. Sci. 104 (25):
10506–11. doi:10.1073/pnas.0701257104. PMC 1890565.
Mooney, H. A.; Cleland, E. E. (2001). "The evolutionary
impact of invasive species". PNAS 98 (10): 5446–5451.
doi:10.1073/pnas.091093398. PMC 33232. PMID 11344292.
Glossary: definitions from the following publication:
Aubry, C., R. Shoal and V. Erickson. 2005. Grass cultivars:
their origins, development, and use on national forests
and grasslands in the Pacific Northwest. USDA Forest
Service. 44 pages, plus appendices.; Native Seed Network
(NSN), Institute for Applied Ecology, 563 SW Jefferson
Ave, Corvallis, OR 97333, USA
"Australia's state of the forests report". 2003.
Rhymer, J. M.; Simberloff, D. (November 1996). "Extinction
by Hybridization and Introgression". Annual Review of
Ecology and Systematics (Annual Reviews) 27: 83–109.
doi:10.1146/annurev.ecolsys.27.1.83. "Introduced species,
in turn, are seen as competing with or preying on native
species or destroying their habitat. Introduces species
(or subspecies), however, can generate another kind
of extinction, a genetic extinction by hybridization
and introgression with native flora and fauna."
Potts, Brad M. (September 2001). Robert C. Barbour,
Andrew B. Hingston. Genetic pollution from farm forestry
using eucalypt species and hybrids : a report for the
RIRDC/L&WA/FWPRDC Joint Venture Agroforestry Program
(Australian Government, Rural Industrial Research and
Development Corporation). ISBN 0-642-58336-6.
"GENETIC DIVERSITY". 2003. p. 104. Retrieved 2010-05-30.
"In other words, greater genetic diversity can offer
greater resilience. In order to maintain the capacity
of our forests to adapt to future changes, therefore,
genetic diversity must be preserved"
Lindenmayer, D. B.; Hobbs, R. J.; Salt, D. (2003-01-06).
"Plantation forests and biodiversity conservation".
Australian Forestry 66 (1): 64. "there may be genetic
invasion from pollen dispersal and subsequent hybridisation
between eucalypt tree species used to establish plantations
and eucalypts endemic to an area (Potts et al. 2001).
This may, in turn, alter natural patterns of genetic
Clover, Charles (2004). The End of the Line: How
overfishing is changing the world and what we eat. London:
Ebury Press. ISBN 0-09-189780-7.
Lee, Anita. "The Pleistocene Overkill Hypothesis."
University of California at Berkeley Geography Program.'.'
Retrieved January 11, 2007.
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Dunn, Robert; Nyeema Harris, Robert Colwell, Lian
Pin Koh, Navjot Sodhi (2009). "Proceedings of the Royal
Society". The sixth mass coextinction: are most endangered
species parasites and mutualists?. The Royal Society.
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Sahney, S., Benton, M.J. & Falcon-Lang, H.J. (2010).
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Thomas, C. D.; et al. (2004-01-08). "Extinction risk
from climate change". Nature 427 (6970): 145–148. doi:10.1038/nature02121.
PMID 14712274. Retrieved 2010-05-28. "minimal climate-warming
scenarios produce lower projections of species committed
to extinction (approx18%)" (Letter to Nature received
10 September 2003.)
Battachatya, Shaoni. ." Retrieved September 15,
Bhattacharya, Shaoni (7 January 2004). "Global warming
threatens millions of species". New Scientist. Retrieved
2010-05-28. "the effects of climate change should be
considered as great a threat to biodiversity as the
"Big Three" - habitat destruction, invasions by alien
species and overexploitation by humans."
Handwerk, Brian, and Brian Hendwerk. "Global Warming
Could Cause Mass Extinctions by 2050, Study Says." National
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