Overpopulation: Difference between revisions
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{{see also|Human overpopulation}} |
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'''Overpopulation''' occurs when a [[population]] of a [[species]] exceeds the [[carrying capacity]] of its [[ecological niche]]. Overpopulation is a function of the number of individuals compared to the relevant resources, such as the water and essential nutrients they need to survive. It can result from an increase in [[List of countries and territories by fertility rate|births]], a decline in [[mortality rate]]s, an increase in [[immigration]], or an [[Sustainability|unsustainable]] [[biome]] and depletion of resources.<ref>{{cite web|title=Dhirubhai Ambani International Model United Nations 2013|url=http://www.daimun.org/pdf/ecosoc3_taraparambi.pdf|website=Daimun|accessdate=29 September 2014}}</ref> |
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==Animal overpopulation== |
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In the wilderness, the problem of overpopulation of species is often solved by growth in the population of [[predator]]s. Predators tend to look for signs of weakness in their prey, and therefore usually first eat the old or sick animals. This has the side effects of controlling the prey population and ensuring its [[evolution]] in favor of genetic characteristics that enhance escape from predation (and the predator may [[co-evolution|co-evolve]], in response).<ref>{{cite web|last1=Scott|first1=Joe|title=Predators and their prey - why we need them both|url=http://www.conservationnw.org/what-we-do/predators-and-prey/carnivores-predators-and-their-prey|website=Conservation Northwest|accessdate=30 September 2014}}</ref> |
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In the absence of predators, species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation, at least in the short term. An abundant supply of resources can produce a ''population boom'' that ends up with more individuals than the environment can support. In this case, starvation, thirst and sometimes violent competition for scarce resources may affect a sharp reduction in population in a very short lapse (a ''population crash''). [[Lemming]]s, as well as other species of [[rodent]]s, are known to have such cycles of rapid population growth and subsequent decrease. |
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Some species seem to have a measure of self-control, by which individuals refrain from mating when they find themselves in a crowded environment. This voluntary abstinence may be induced by stress or by [[pheromone]]s. |
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In an ideal setting, when animal populations grow, so do the number of predators that feed on that particular animal. Animals that have [[birth defect]]s or weak [[gene]]s (such as the runt of the litter) are unable to compete over food with stronger, healthier animals. |
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In reality, an animal that is not native to an environment may have advantages over the native ones, such being unsuitable for the local predators. If left uncontrolled, such an animal can quickly overpopulate and ultimately destroy its environment. |
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==Examples== |
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Examples of overpopulation caused by '''introduction of a foreign species''' abound: <!-- this deserves an entire article, if there is none --> |
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* In the [[Argentina|Argentine]] [[Patagonia]], for example, European species such as the [[trout]] and the [[deer]] were introduced into the local streams and forests, respectively, and quickly became a plague, competing with and sometimes driving away the local species of fish and [[ruminant]]s.<ref>{{cite web|last1=Speziale|first1=Karina|last2=Sergio|first2=Lambertucci|last3=Jose´|first3=Tella|last4=Martina|first4=Carrete|title=Dealing with Non-native Species: what makes the Difference in South America?|url=http://digital.csic.es/bitstream/10261/64587/1/biolInv.pdf|website=Digital.CSIC Open Science|accessdate=2 October 2014}}</ref> |
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* In [[Australia]], when [[Rabbits in Australia|rabbits were introduced by European immigrants]], they bred out of control and ate the farm crops and food that both native and farm animals needed. Farmers hunted the rabbits, and also brought cats in to guard against rabbits and rats. These introduced cats created another problem, becoming predators of local species.<ref>{{cite web|last1=Zukerman|first1=Wendy|title=Australia's Battle with the Bunny|url=http://www.abc.net.au/science/articles/2009/04/08/2538860.htm|website=ABC Science|date=2009}}</ref> |
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Examples of overpopulation caused by '''natural cyclic variations''' include: |
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*the [[2004 Locust Outbreak]] in West and North Africa. |
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*the [[Australian Plague Locust Commission|Australian locust plagues]]. |
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*[[Palestine (region)|Palestine]]'s eight-month-long [[1915 locust plague]]. |
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==Human overpopulation== |
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{{main|Human overpopulation}} |
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The [[human population]] has been growing continuously since the end of the [[Black Death]], around the year 1400, although the most significant increase has been in the last 50 years, mainly due to [[History of medicine#Modern medicine|medical advancements]], increases in agricultural productivity and the historically unique availability of abundant cheap energy. The rate of population growth has been declining since the 1980s. Most contemporary{{clarify|Within this generation, 1/2 billion is also suggested|date=April 2015}} estimates for the carrying capacity of the [[Earth]] under existing conditions are between 4 billion and 16 billion.{{citation needed|reason=Is there someone proposing the earth can sustain 16 billion? Who?|date=April 2015}} In 2013 the human population was 7 billion. By 2025 the world population is expected to grow by an additional 1 billion.<ref>{{cite web|title=What’s Next for Our Increasingly Overpopulated World?|url=http://diplomacy.norwich.edu/overpopulated-world/|website=Norwich University|accessdate=29 September 2014}}</ref> Depending on which estimate of overpopulation is used, human overpopulation may or may not have already occurred. |
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The [[IAP statement on population growth|InterAcademy Panel Statement on Population Growth]], circa 1994, has stated that many environmental problems, such as rising levels of [[atmospheric carbon dioxide]], [[global warming]], and [[pollution]], are aggravated by the population expansion.<ref>[https://web.archive.org/web/20100210203604/http://www.interacademies.net/?id=3547 Joint statement by fifty-eight of the world's scientific academies]. interacademies.net</ref> Other problems associated with overpopulation include the increased demand for resources such as fresh water and food, [[starvation]] and [[malnutrition]], consumption of natural resources (such as [[fossil fuels]]) faster than the rate of regeneration, and a deterioration in living conditions.<ref>Zinkina J., Korotayev A. [http://cliodynamics.ru/index.php?option=com_content&task=view&id=360&Itemid=1 Explosive Population Growth in Tropical Africa: Crucial Omission in Development Forecasts (Emerging Risks and Way Out). ''World Futures'' 70/2 (2014): 120–139].</ref> However, some believe that [[waste]] and [[over-consumption]], especially by wealthy nations, is putting more strain on the environment than overpopulation.<ref>{{cite web|url=http://e360.yale.edu/feature/consumption_dwarfs_population_as_main_environmental_threat/2140/ |title=Consumption Dwarfs Population as Main Environmental Threat|author=Fred Pearce|publisher=Yale University |date=2009-04-13|accessdate=2012-11-12}}</ref> |
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==Overpopulation in domestic animals== |
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{{main|Overpopulation in domestic animals}} |
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Ethical issues of humaneness arise also from the unintended population growth of dogs, cats, and other domestic animals. Outcomes include [[euthanization]] of former pets and release of former pets to the wild. |
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==See also== |
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*[[Animal population control]] |
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*[[Culling]] |
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*[[Cascade effect]] |
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*[[Overexploitation]] |
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==References== |
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{{reflist}} |
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{{modelling ecosystems|expanded=other}} |
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[[Category:Population ecology]] |
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[[Category:Population density]] |
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[[Category:Zoology]] |
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Revision as of 00:07, 2 October 2015
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