Editing Extinction (section)

==Causes==
[[File:Ectopistes migratoriusMCN2P28CA.jpg|thumb|upright|The [[passenger pigeon]], one of the hundreds of species of extinct birds, was hunted to extinction over the course of a few decades.]]

As long as species have been evolving, species have been going extinct. It is estimated that over 99.9% of all species that ever lived are extinct. The average lifespan of a species is 1–10&nbsp;million years,<ref>{{Cite book |title=Conservation of Wildlife Populations: Demography, Genetics and Management |url=https://books.google.com/books?id=fVLEV64qYfcC |publisher=John Wiley & Sons |year=2009 |isbn=978-1-4443-0893-8 |language=en |first=L. Scott |last=Mills |page=13}}</ref> although this varies widely between taxa.
A variety of causes can contribute directly or indirectly to the extinction of a species or group of species. "Just as each species is unique", write Beverly and [[Stephen C. Stearns]], "so is each extinction&nbsp;... the causes for each are varied—some subtle and complex, others obvious and simple".<ref name="Stearns">{{cite book |last=Stearns |first=Beverly Peterson and Stephen C. |title=Watching, from the Edge of Extinction |publisher=Yale University Press |year=2000 |isbn=978-0-300-08469-6 |pages=x |chapter=Preface |url=https://archive.org/details/isbn_9780300084696}}</ref> Most simply, any species that cannot [[Survival skills|survive]] and [[reproduction|reproduce]] in its environment and cannot move to a new environment where it can do so, dies out and becomes extinct. Extinction of a species may come suddenly when an otherwise healthy species is wiped out completely, as when [[toxic]] [[pollution]] renders its entire [[habitat]] unliveable; or may occur gradually over thousands or millions of years, such as when a species gradually loses out in competition for food to better adapted competitors. Extinction may occur a long time after the events that set it in motion, a phenomenon known as [[extinction debt]].

Assessing the relative importance of genetic factors compared to environmental ones as the causes of extinction has been compared to the debate on [[nature and nurture]].<ref name="Raup">{{cite journal |last=Raup |first=David M. |author2=J. John Sepkoski Jr. |s2cid=43002817 |date=March 1982 |title=Mass extinctions in the marine fossil record |journal=Science |volume=215 |issue=4539 |pages=1501–1503 |doi=10.1126/science.215.4539.1501 |pmid=17788674 |bibcode=1982Sci...215.1501R}}</ref> The question of whether more extinctions in the [[fossil]] record have been caused by [[evolution]] or by competition or by predation or by disease or by catastrophe is a subject of discussion; Mark Newman, the author of ''Modeling Extinction'', argues for a mathematical model that falls in all positions.<ref name="Newman" /> By contrast, [[conservation biology]] uses the [[extinction vortex]] model to classify extinctions by cause. When concerns about [[human extinction]] have been raised, for example in Sir [[Martin Rees]]' 2003 book ''[[Our Final Hour]]'', those concerns lie with the effects of [[climate change]] or [[technology|technological]] disaster.

Human-driven extinction started as humans migrated out of Africa more than 60,000 years ago.<ref>{{cite journal |editor1-last=Johns |editor1-first=David |editor2-last=Crist |editor2-first=Eileen |editor3-last=Sahgal |editor3-first=Bittu |date=2022 |title=Ending the Colonization of the Non-Human World |url=https://www.sciencedirect.com/journal/biological-conservation/special-issue/10574WDL8SQ |journal=[[Biological Conservation (journal)|Biological Conservation]] |volume= |issue= |pages= |doi= |access-date= |archive-date=18 November 2022 |archive-url=https://web.archive.org/web/20221118015916/https://www.sciencedirect.com/journal/biological-conservation/special-issue/10574WDL8SQ |url-status=live}}</ref> Currently, environmental groups and some governments are concerned with the extinction of species caused by humanity, and they try to prevent further extinctions through a variety of [[conservation movement|conservation]] programs.<ref name="MSNBC" /> Humans can cause extinction of a species through [[overharvesting]], [[pollution]], [[habitat destruction]], introduction of [[invasive species]] (such as new [[predator]]s and food [[competitors]]), overhunting, and other influences. Explosive, unsustainable human [[population growth]] and [[Overconsumption|increasing per capita consumption]] are essential drivers of the extinction crisis.<ref name="Ceballos2017"/><ref>{{cite journal |last1=Stokstad |first1=Erik |title=Landmark analysis documents the alarming global decline of nature |journal=Science |date=6 May 2019 |doi=10.1126/science.aax9287 |s2cid=166478506}}</ref><ref>{{cite journal |last1=Andermann |first1=Tobias |last2=Faurby |first2=Søren |last3=Turvey |first3=Samuel T. |last4=Antonelli |first4=Alexandre |last5=Silvestro |first5=Daniele |title=The past and future human impact on mammalian diversity |journal=Science Advances |date=1 September 2020 |volume=6 |issue=36 |pages=eabb2313 |doi=10.1126/sciadv.abb2313 |pmid=32917612 |s2cid=221498762 |doi-access=free |pmc=7473673 |bibcode=2020SciA....6.2313A}} [[File:CC-BY icon.svg|50px]]  Text and images are available under a [https://creativecommons.org/licenses/by/4.0/  Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=16 October 2017 }}.</ref><ref>{{cite news |last=Lewis |first=Sophie |date=September 9, 2020 |title=Animal populations worldwide have declined by almost 70% in just 50 years, new report says |url=https://www.cbsnews.com/news/biodiversity-endangered-species-animal-population-decline-world-wildlife-fund-report-2020-09-09/ |work=[[CBS News]] |access-date=October 22, 2020 |archive-date=10 September 2020 |archive-url=https://web.archive.org/web/20200910152119/https://www.cbsnews.com/news/biodiversity-endangered-species-animal-population-decline-world-wildlife-fund-report-2020-09-09/ |url-status=live}}</ref> According to the [[International Union for Conservation of Nature]] (IUCN), 784 extinctions have been recorded since the year 1500, the arbitrary date selected to define "recent" extinctions, up to the year 2004; with many more likely to have gone unnoticed. Several species have also been listed as extinct since 2004.<ref name="IUCNno">{{cite web |publisher=[[World Conservation Union]] |url=http://www.iucn.org/themes/ssc/red_list_2004/GSAexecsumm_EN.htm |archive-url=https://web.archive.org/web/20060827093621/http://www.iucn.org/themes/ssc/red_list_2004/GSAexecsumm_EN.htm |url-status=dead |archive-date=27 August 2006 |title=2004 Red List |work=IUCN Red List of Threatened Species |access-date=September 20, 2006}}</ref>

=== Genetics and demographic phenomena ===
{{See also|Extinction vortex|Genetic erosion|Mutational meltdown}}
If [[adaptation]] increasing population [[fitness (biology)|fitness]] is slower than [[environmental degradation]] plus the accumulation of slightly deleterious [[mutation]]s, then a population will go extinct.<ref>{{cite journal |last1=Bertram |first1=J |last2=Gomez |first2=K |last3=Masel |first3=J |title=Predicting patterns of long-term adaptation and extinction with population genetics |journal=Evolution |date=February 2017 |volume=71 |issue=2 |pages=204–214 |doi=10.1111/evo.13116 |pmid=27868195 |arxiv=1605.08717 |s2cid=4705439}}</ref> Smaller populations have fewer beneficial mutations entering the population each generation, slowing adaptation. It is also easier for slightly deleterious mutations to [[fixation (population genetics)|fix]] in small populations; the resulting positive feedback loop between small population size and low fitness can cause [[mutational meltdown]].

Limited geographic range is the most important determinant of [[genus]] extinction at background rates but becomes increasingly irrelevant as [[#Mass extinctions|mass extinction]] arises.<ref>{{cite journal |author1=Payne, J.L. |author2=S. Finnegan |year=2007 |title=The effect of geographic range on extinction risk during background and mass extinction |journal=[[PNAS|Proc. Natl. Acad. Sci.]] |volume=104 |issue=25 |pages=10506–10511 |doi=10.1073/pnas.0701257104 |pmid=17563357 |pmc=1890565 |bibcode=2007PNAS..10410506P |doi-access=free}}</ref> Limited geographic range is a cause both of small population size and of greater vulnerability to local environmental catastrophes.

Extinction rates can be affected not just by population size, but by any factor that affects [[evolvability]], including [[balancing selection]], [[cryptic genetic variation]], [[phenotypic plasticity]], and [[robustness (evolution)|robustness]]. A diverse or deep [[gene pool]] gives a population a higher chance in the short term of surviving an adverse change in conditions. Effects that cause or reward a loss in [[genetic diversity]] can increase the chances of extinction of a species. [[Population bottleneck]]s can dramatically reduce genetic diversity by severely limiting the number of reproducing individuals and make [[inbreeding]] more frequent.

=== Genetic pollution ===
{{Main|Genetic pollution}}
Extinction sometimes results for species evolved to specific ecologies<ref>{{cite journal |last=Mooney |first=H.A. |author2=Cleland, E.E. |year=2001 |title=The evolutionary impact of invasive species |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=98 |issue=10 |pages=5446–5451 |doi=10.1073/pnas.091093398 |pmid=11344292 |pmc=33232 |bibcode=2001PNAS...98.5446M |doi-access=free}}</ref> that are subjected to [[genetic pollution]]—i.e., uncontrolled [[Hybrid (biology)|hybridization]], [[introgression]] and genetic swamping that lead to homogenization or [[Fitness (biology)|out-competition]] from the introduced ([[Heterosis|or hybrid]]) species.<ref>{{cite web |url=http://www.nativeseednetwork.org/article_view?id=13 |title=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 |archive-url=https://web.archive.org/web/20060222092651/http://www.nativeseednetwork.org/article_view?id=13 |archive-date=22 February 2006 |url-status=dead}}</ref> Endemic populations can face such extinctions when new populations are imported or [[selective breeding|selectively bred]] by people, or when habitat modification brings previously isolated species into contact. Extinction is likeliest for [[rare species]] coming into contact with more abundant ones;<ref name="RareEucalypts"/> [[interbreeding]] can swamp the rarer gene pool and create hybrids, depleting the purebred gene pool (for example, the endangered [[wild water buffalo]] is most threatened with extinction by genetic pollution from [[Water buffalo|the abundant domestic water buffalo]]). Such extinctions are not always apparent from [[morphology (biology)|morphological]] (non-genetic) observations. Some degree of [[gene flow]] is a normal evolutionary process; nevertheless, hybridization (with or without introgression) threatens rare species' existence.<ref>{{cite journal |title=Extinction by Hybridization and Introgression |first1=J.M. |last1=Rhymer |first2=D. |last2=Simberloff |journal=Annual Review of Ecology and Systematics |date=November 1996 |volume=27 |issue=1 |pages=83–109 |doi=10.1146/annurev.ecolsys.27.1.83 |publisher=Annual Reviews |quote=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 |jstor=2097230 |bibcode=1996AnRES..27...83R}}</ref><ref>{{cite book |title=Genetic pollution from farm forestry using eucalypt species and hybrids : a report for the RIRDC/L&WA/FWPRDC Joint Venture Agroforestry Program |first1=Brad M. |last1=Potts |others=Robert C. Barbour, Andrew B. Hingston |date=September 2001 |isbn=978-0-642-58336-9 |publisher=Australian Government, Rural Industrial Research and Development Corporation}}</ref>

The gene pool of a [[species]] or a [[population]] is the variety of genetic information in its living members. A large gene pool (extensive [[genetic diversity]]) is associated with robust populations that can survive bouts of intense [[Selection (biology)|selection]]. Meanwhile, low genetic diversity (see [[inbreeding]] and [[population bottlenecks]]) reduces the range of adaptions possible.<ref>
{{cite web |url=http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |title=Genetic diversity |page=104 |year=2003 |access-date=2010-05-30 |quote=In other words, greater genetic diversity can offer greater resilience. In order to maintain the capacity of our forests to [[adaption|adapt]] to future changes, therefore, genetic diversity must be preserved |url-status=dead |archive-url=https://web.archive.org/web/20110313092336/http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |archive-date=2011-03-13}}</ref> Replacing native with alien genes narrows genetic diversity within the original population,<ref name="RareEucalypts">
{{cite web |url=http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |title=Australia's state of the forests report |page=107 |year=2003 |url-status=dead |archive-url=https://web.archive.org/web/20110313092336/http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |archive-date=2011-03-13}}</ref><ref>{{cite journal |last1=Lindenmayer |first1=D. B. |last2=Hobbs |first2=R. J. |last3=Salt |first3=D. |title=Plantation forests and biodiversity conservation |journal=Australian Forestry |date=January 2003 |volume=66 |issue=1 |pages=62–66 |doi=10.1080/00049158.2003.10674891 |bibcode=2003AuFor..66...62L |s2cid=53968395 |url=https://researchrepository.murdoch.edu.au/id/eprint/4637/1/plantation_forests.pdf |access-date=9 February 2022 |archive-date=17 February 2022 |archive-url=https://web.archive.org/web/20220217143102/https://researchrepository.murdoch.edu.au/id/eprint/4637/1/plantation_forests.pdf |url-status=live}}</ref> thereby increasing the chance of extinction.

=== Habitat degradation ===
{{Main|Habitat destruction}}
[[File:DirkvdM santa fe scorched.jpg|thumb|upright=1.2|Scorched land resulting from [[slash-and-burn]] agriculture]]
Habitat degradation is currently the main anthropogenic cause of species extinctions. The main cause of habitat degradation worldwide is agriculture, with [[urban sprawl]], logging, mining, and some fishing practices close behind. The degradation of a species' [[habitat (ecology)|habitat]] may alter the [[fitness landscape]] to such an extent that the species is no longer able to survive and becomes extinct. This may occur by direct effects, such as the environment becoming [[toxicity|toxic]], or indirectly, by limiting a species' ability to compete effectively for diminished resources or against new competitor species.

Habitat destruction, particularly the removal of vegetation that stabilizes soil, enhances erosion and diminishes nutrient availability in terrestrial ecosystems. This degradation can lead to a reduction in agricultural productivity. Furthermore, increased erosion contributes to poorer water quality by elevating the levels of sediment and pollutants in rivers and streams.<ref>{{Cite web |title=Habitat loss / restoration |url=https://ugc.berkeley.edu/background-content/habitat-loss-restoration/ |access-date=2024-04-12 |website=Understanding Global Change |language=en-US}}</ref>

Habitat degradation through toxicity can kill off a species very rapidly, by killing all living members through [[contamination]] or [[Sterilization (microbiology)|sterilizing]] them. It can also occur over longer periods at lower toxicity levels by affecting life span, reproductive capacity, or competitiveness.

Habitat degradation can also take the form of a physical destruction of niche habitats. The widespread destruction of [[tropical rainforest]]s and replacement with open pastureland is widely cited as an example of this;<ref name="Wilson" /> elimination of the dense forest eliminated the infrastructure needed by many species to survive. For example, a [[fern]] that depends on dense shade for protection from direct sunlight can no longer survive without forest to shelter it. Another example is the destruction of ocean floors by [[bottom trawling]].<ref>{{cite book |last=Clover |first=Charles |year=2004 |title=The End of the Line: How overfishing is changing the world and what we eat |publisher=Ebury Press |location=London |isbn=978-0-09-189780-2}}</ref>

Diminished resources or introduction of new competitor species also often accompany habitat degradation. [[Global warming]] has allowed some species to expand their range, bringing competition to other species that previously occupied that area. Sometimes these new competitors are predators and directly affect prey species, while at other times they may merely outcompete vulnerable species for limited resources. Vital resources including [[water]] and food can also be limited during habitat degradation, leading to extinction.

=== Predation, competition, and disease ===
{{See also|Island restoration}}
[[File:Bufo periglenes2.jpg|thumb|The [[golden toad]] was last seen on May 15, 1989. [[Decline in amphibian populations]] is ongoing worldwide.]]
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, [[interspecific 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 geological time, humans have become an additional cause of extinction of some species, either as a new mega-predator or by [[introduced species|transporting]] [[animal]]s and [[plant]]s from one part of the world to another. Such introductions have been occurring for thousands of years, sometimes intentionally (e.g. [[livestock]] released by sailors on islands as a future source of food) and sometimes accidentally (e.g. [[rat]]s escaping from boats). In most cases, the introductions are unsuccessful, but when an [[Invasive species|invasive alien species]] does become established, the consequences can be catastrophic. Invasive alien species can affect [[Endemic (ecology)|native]] species directly by eating them, competing with them, and introducing [[pathogen]]s or [[parasite]]s 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 America|North]] and [[South America]] (12,000 years before present), [[Madagascar]], [[Hawaii]] (AD 300–1000), and New Zealand (AD 1300–1500), 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.<ref name="Lee">Lee, Anita. "[http://geography.berkeley.edu/ProgramCourses/CoursePagesFA2002/geog148/Term%20Papers/Anita%20Lee/THEPLE~1.html The Pleistocene Overkill Hypothesis] {{webarchive |url=https://web.archive.org/web/20061014100508/http://geography.berkeley.edu/ProgramCourses/CoursePagesFA2002/geog148/Term%20Papers/Anita%20Lee/THEPLE~1.html |date=October 14, 2006 }}." ''University of California at Berkeley Geography Program.'' Retrieved January 11, 2007.</ref>

=== Coextinction ===
{{Main|Coextinction}}
[[File:Giant Haasts eagle attacking New Zealand moa.jpg|thumb|The large [[Haast's eagle]] and [[moa]] from New Zealand]]

Coextinction refers to the loss of a species due to the extinction of another; for example, the extinction of [[parasitism|parasitic]] insects following the loss of their hosts. Coextinction can also occur when a species loses its [[pollinator]], or to [[predator]]s in a [[food chain]] who lose their prey. "Species coextinction is a manifestation of one of the interconnectednesses of organisms in complex ecosystems&nbsp;... While coextinction may not be the most important cause of species extinctions, it is certainly an insidious one."<ref name="Koh">{{cite journal |last1=Koh |first1=Lian Pin |last2=Dunn |first2=Robert R. |last3=Sodhi |first3=Navjot S. |last4=Colwell |first4=Robert K. |last5=Proctor |first5=Heather C. |last6=Smith |first6=Vincent S. |title=Species Coextinctions and the Biodiversity Crisis |journal=Science |date=10 September 2004 |volume=305 |issue=5690 |pages=1632–1634 |doi=10.1126/science.1101101 |pmid=15361627 |bibcode=2004Sci...305.1632K |s2cid=30713492}}</ref> Coextinction is especially common when a [[keystone species]] goes extinct. Models suggest that coextinction is the most common form of [[biodiversity loss]]. There may be a cascade of coextinction across the [[trophic level]]s. Such effects are most severe in [[mutualism (biology)|mutualistic]] and parasitic relationships. An example of coextinction is the [[Haast's eagle]] and the [[moa]]: the Haast's eagle was a predator that became extinct because its food source became extinct. The moa were several species of flightless birds that were a food source for the Haast's eagle.<ref>{{cite journal |last1=Dunn |first1=Robert R. |last2=Harris |first2=Nyeema C. |last3=Colwell |first3=Robert K. |last4=Koh |first4=Lian Pin |last5=Sodhi |first5=Navjot S. |title=The sixth mass coextinction: are most endangered species parasites and mutualists? |journal=Proceedings of the Royal Society B: Biological Sciences |date=7 September 2009 |volume=276 |issue=1670 |pages=3037–3045 |doi=10.1098/rspb.2009.0413 |pmid=19474041 |pmc=2817118}}</ref>

=== Climate change ===
{{Main|Extinction risk from climate change}}
{{See also|Effect of climate change on plant biodiversity|Effects of climate change on marine mammals}}

Extinction as a result of [[climate change]] has been confirmed by fossil studies.<ref name="SahneyBentonFalconLang 2010RainforestCollapse">{{cite journal |url=http://geology.geoscienceworld.org/cgi/content/abstract/38/12/1079 |last1=Sahney |first1=S. |last2=Benton |first2=M.J. |last3=Falcon-Lang |first3=H.J. |year=2010 |title=Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica |journal=Geology |doi=10.1130/G31182.1 |volume=38 |pages=1079–1082 |format=PDF |issue=12 |bibcode=2010Geo....38.1079S |access-date=28 August 2011 |archive-date=11 October 2011 |archive-url=https://web.archive.org/web/20111011144357/http://geology.geoscienceworld.org/cgi/content/abstract/38/12/1079 |url-status=live|url-access=subscription }}</ref> Particularly, the extinction of amphibians during the [[Carboniferous Rainforest Collapse]], 305&nbsp;million years ago.<ref name="SahneyBentonFalconLang 2010RainforestCollapse" /> A 2003 review across 14 biodiversity research centers predicted that, because of climate change, 15–37% of land species would be "committed to extinction" by 2050.<ref>{{cite journal |last1=Thomas |first1=Chris D. |last2=Cameron |first2=Alison |last3=Green |first3=Rhys E. |last4=Bakkenes |first4=Michel |last5=Beaumont |first5=Linda J. |last6=Collingham |first6=Yvonne C. |last7=Erasmus |first7=Barend F. N. |last8=de Siqueira |first8=Marinez Ferreira |last9=Grainger |first9=Alan |last10=Hannah |first10=Lee |last11=Hughes |first11=Lesley |last12=Huntley |first12=Brian |last13=van Jaarsveld |first13=Albert S. |last14=Midgley |first14=Guy F. |last15=Miles |first15=Lera |last16=Ortega-Huerta |first16=Miguel A. |last17=Townsend Peterson |first17=A. |last18=Phillips |first18=Oliver L. |last19=Williams |first19=Stephen E. |title=Extinction risk from climate change |journal=Nature |date=January 2004 |volume=427 |issue=6970 |pages=145–148 |doi=10.1038/nature02121 |pmid=14712274 |bibcode=2004Natur.427..145T |s2cid=969382 |url=https://pure.qub.ac.uk/ws/files/733227/Thomas%26Cameron_Extinctions_Cover%26Article_Nature_2004.pdf |access-date=30 November 2019 |archive-date=29 April 2019 |archive-url=https://web.archive.org/web/20190429130413/https://pure.qub.ac.uk/ws/files/733227/Thomas%26Cameron_Extinctions_Cover%26Article_Nature_2004.pdf |url-status=live}}</ref><ref name="Bhattacharya">{{cite magazine |url=https://www.newscientist.com/article/dn4545-global-warming-threatens-millions-of-species.html |title=Global warming threatens millions of species |date=7 January 2004 |magazine=[[New Scientist]] |access-date=2010-05-28 |last=Bhattacharya |first=Shaoni |quote=the effects of climate change should be considered as great a threat to biodiversity as the "Big Three"—[[habitat destruction]], [[Invasive species|invasions by alien species]] and overexploitation by humans. |archive-date=21 April 2010 |archive-url=https://web.archive.org/web/20100421082210/http://www.newscientist.com/article/dn4545-global-warming-threatens-millions-of-species.html |url-status=live}}</ref> The ecologically rich areas that would potentially suffer the heaviest losses include the [[Cape Floristic Region]] and the [[Caribbean Basin]]. These areas might see a doubling of present carbon dioxide levels and rising temperatures that could eliminate 56,000 plant and 3,700 animal species.<ref>{{cite web |last1=Handwerk |first1=Brian |last2=Hendwerk |first2=Brian |title=Global Warming Could Cause Mass Extinctions by 2050, Study Says |publisher=National Geographic News |date=April 2006 |url=https://news.nationalgeographic.com/news/2006/04/0412_060412_global_warming.html |access-date=27 October 2017 |archive-date=12 June 2017 |archive-url=https://web.archive.org/web/20170612161507/http://news.nationalgeographic.com/news/2006/04/0412_060412_global_warming.html |url-status=dead}}</ref> Climate change has also been found to be a factor in [[habitat loss]] and [[desertification]].<ref>{{cite journal |last1=Gibbon |first1=J. Whitfield |last2=Scott |first2=David E. |last3=Ryan |first3=Travis J. |last4=Buhlmann |first4=Kurt A. |last5=Tuberville |first5=Tracey D. |last6=Metts |first6=Brian S. |last7=Greene |first7=Judith L. |last8=Mills |first8=Tony |last9=Leiden |first9=Yale |last10=Poppy |first10=Sean |last11=Winne |first11=Christopher T. |title=The Global Decline of Reptiles, Déjà Vu Amphibians |journal=BioScience |date=2000 |volume=50 |issue=8 |pages=653 |doi=10.1641/0006-3568(2000)050[0653:TGDORD]2.0.CO;2 |s2cid=12094030 |url=https://digitalcommons.butler.edu/facsch_papers/536 |access-date=14 July 2019 |archive-date=13 December 2019 |archive-url=https://web.archive.org/web/20191213114220/https://digitalcommons.butler.edu/facsch_papers/536/ |url-status=live|url-access=subscription }}</ref>

=== Sexual selection and male investment ===
Studies of fossils following species from the time they evolved to their extinction show that species with high [[sexual dimorphism]], especially characteristics in males that are used to compete for mating, are at a higher risk of extinction and die out faster than less sexually dimorphic species, the least sexually dimorphic species surviving for millions of years while the most sexually dimorphic species die out within mere thousands of years. Earlier studies based on counting the number of currently living species in modern taxa have shown a higher number of species in more sexually dimorphic taxa which have been interpreted as higher survival in taxa with more sexual selection, but such studies of modern species only measure indirect effects of extinction and are subject to error sources such as dying and doomed taxa speciating more due to splitting of habitat ranges into more small isolated groups during the habitat retreat of taxa approaching extinction. Possible causes of the higher extinction risk in species with more sexual selection shown by the comprehensive fossil studies that rule out such error sources include expensive sexually selected ornaments having negative effects on the ability to survive [[natural selection]], as well as [[sexual selection]] removing a diversity of genes that under current ecological conditions are neutral for natural selection but some of which may be important for surviving climate change.<ref>{{cite journal |last1=Martins |first1=Maria João Fernandes |last2=Puckett |first2=T. Markham |last3=Lockwood |first3=Rowan |last4=Swaddle |first4=John P. |last5=Hunt |first5=Gene |title=High male sexual investment as a driver of extinction in fossil ostracods |journal=Nature |date=April 2018 |volume=556 |issue=7701 |pages=366–369 |doi=10.1038/s41586-018-0020-7 |pmid=29643505 |bibcode=2018Natur.556..366M |s2cid=4925632 |url=https://aquila.usm.edu/cgi/viewcontent.cgi?article=17927&context=fac_pubs |access-date=16 September 2022 |archive-date=2 October 2022 |archive-url=https://web.archive.org/web/20221002122147/https://aquila.usm.edu/cgi/viewcontent.cgi?article=17927&context=fac_pubs |url-status=live|url-access=subscription }}</ref>