Agriculture: Difference between revisions

{{Use American English|date=March 2016}}

[[File:Farm in Hainan 01.jpg|thumb|upright=1.2|right|China has the largest agricultural output of any country.<ref name=UNCTAD2017 />]]

'''Agriculture''' or '''farming''' is the practice of cultivating [[plants]] and [[livestock]].<ref name="Office1999">{{cite book |title=Safety and health in agriculture |url={{google books|plainurl=y|id=GtBa6XIW_aQC|page=77}} |year=1999 |publisher=International Labour Organization |isbn=978-92-2-111517-5 |page=77 |access-date=13 September 2010 |url-status=live |archive-url=https://web.archive.org/web/20110722061757/http://books.google.com/books?id=GtBa6XIW_aQC |archive-date=22 July 2011|quote=defined agriculture as 'all forms of activities connected with growing, harvesting and primary processing of all types of crops, with the breeding, raising and caring for animals, and with tending gardens and nurseries'.}}</ref> Agriculture was the key development in the rise of [[sedentism|sedentary]] [[human civilization]], whereby farming of [[domestication|domesticated]] species created food [[economic surplus|surpluses]] that enabled people to live in cities. The [[history of agriculture]] began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs, sheep, and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. [[Industrial agriculture]] based on large-scale [[monoculture]] in the twentieth century came to dominate agricultural output, though about 2&nbsp;billion people still depended on [[subsistence agriculture]].

 

Modern [[agronomy]], [[plant breeding]], [[agrochemical]]s such as [[pesticide]]s and [[fertilizer]]s, and technological developments have sharply increased crop yields, but causing [[Environmental impact of agriculture|ecological and environmental damage]]. [[Selective breeding]] and modern practices in [[animal husbandry]] have similarly increased the output of meat, but have raised concerns about [[animal welfare]] and environmental damage. Environmental issues include contributions to [[global warming]], depletion of [[aquifer]]s, [[deforestation]], [[antibiotic resistance]], and [[growth hormone]]s in [[industrial meat production]]. Agriculture is both a cause of and sensitive to [[environmental degradation]], such as [[biodiversity loss]], [[desertification]], [[soil degradation]] and [[Effects of climate change on agriculture|global warming]], all of which can cause decreases in crop yield. [[Genetically modified organism]]s are widely used, although some are banned in certain countries.

It may also be broadly decomposed into '''plant agriculture''', which concerns the cultivation of useful plants,<ref name="Stevenson1971">{{cite journal | last=Stevenson | first=G. C. | title=Plant Agriculture Selected and introduced by Janick Jules and Others San Francisco: Freeman (1970), pp. 246, £2.10 | journal=Experimental Agriculture | publisher=Cambridge University Press (CUP) | volume=7 | issue=4 | year=1971 | issn=0014-4797 | doi=10.1017/s0014479700023371 | pages=363–363}}</ref> and '''animal agriculture''', the production of agricultural animals.<ref name="Herren2012">{{cite book | last=Herren | first=R.V. | title=Science of Animal Agriculture | publisher=Cengage Learning | year=2012 | isbn=978-1-133-41722-4 | url=https://books.google.com.br/books?id=-fQIAAAAQBAJ | access-date=2022-05-01 | page=}}</ref>

The development of agriculture enabled the human population to grow many times larger than could be sustained by [[hunter-gatherer|hunting and gathering]].<ref name=Bocquet-Appel>{{cite journal |author=Bocquet-Appel, Jean-Pierre |title=When the World's Population Took Off: The Springboard of the Neolithic Demographic Transition |journal=Science |date=29 July 2011 |volume=333 |issue=6042 |pages=560–561 |doi=10.1126/science.1208880 |pmid=21798934 |bibcode=2011Sci...333..560B |s2cid=29655920 }}</ref> Agriculture began independently in different parts of the globe,<ref name="Stephens 897–902">{{Cite journal |last1=Stephens |first1=Lucas |last2=Fuller |first2=Dorian |last3=Boivin |first3=Nicole |last4=Rick |first4=Torben |last5=Gauthier |first5=Nicolas |last6=Kay |first6=Andrea |last7=Marwick |first7=Ben |last8=Armstrong |first8=Chelsey Geralda |last9=Barton |first9=C. Michael|date=30 August 2019|title=Archaeological assessment reveals Earth's early transformation through land use |journal=Science |volume=365|issue=6456 |pages=897–902 |doi=10.1126/science.aax1192 |issn=0036-8075 |pmid=31467217 |hdl=10150/634688 |hdl-access=free |bibcode=2019Sci...365..897S |s2cid=201674203}}</ref> and included a diverse range of [[taxa]], in at least 11 separate [[centers of origin]].<ref name="Larson2014">{{cite journal |doi=10.1073/pnas.1323964111 |title=Current perspectives and the future of domestication studies |journal=PNAS |volume=111 |issue=17 |pages=6139–6146 |year=2014 |last1=Larson |first1=G. |last2=Piperno |first2=D. R. |last3=Allaby |first3=R. G. |last4=Purugganan |first4=M. D. |last5=Andersson |first5=L. |last6=Arroyo-Kalin |first6=M. |last7=Barton |first7=L. |last8=Climer Vigueira |first8=C. |last9=Denham |first9=T. |last10=Dobney |first10=K. |last11=Doust |first11=A. N. |last12=Gepts |first12=P. |last13=Gilbert |first13=M. T. P. |last14=Gremillion |first14=K. J. |last15=Lucas |first15=L. |last16=Lukens |first16=L. |last17=Marshall |first17=F. B. |last18=Olsen |first18=K. M. |last19=Pires |first19=J.C. |last20=Richerson |first20=P. J. |last21=Rubio De Casas |first21=R. |last22=Sanjur |first22=O.I. |last23=Thomas |first23=M. G. |last24=Fuller |first24=D.Q. |doi-access=free |pmid=24757054 |pmc=4035915 |bibcode=2014PNAS..111.6139L}}</ref> Wild grains were collected and eaten from at least 105,000 years ago.<ref>{{cite magazine |last1=Harmon |first1=Katherine |title=Humans feasting on grains for at least 100,000 years |url=http://blogs.scientificamerican.com/observations/humans-feasting-on-grains-for-at-least-100000-years/ |magazine=[[Scientific American]] |access-date=28 August 2016 |date=17 December 2009 |url-status=live |archive-url=https://web.archive.org/web/20160917013143/http://blogs.scientificamerican.com/observations/humans-feasting-on-grains-for-at-least-100000-years/ |archive-date=17 September 2016 }}</ref> In the Paleolithic levant, 23,000 years ago, cereals cultivation of [[emmer wheat|emmer]], [[barley]], and [[oats]] has been observed near the sea of Galilee. <ref>{{Cite journal |last=Snir |first=Ainit |last2=Nadel |first2=Dani |last3=Groman-Yaroslavski |first3=Iris |last4=Melamed |first4=Yoel |last5=Sternberg |first5=Marcelo |last6=Bar-Yosef |first6=Ofer |last7=Weiss |first7=Ehud |date=2015-07-22 |title=The Origin of Cultivation and Proto-Weeds, Long Before Neolithic Farming |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131422 |journal=PLOS ONE |language=en |volume=10 |issue=7 |pages=e0131422 |doi=10.1371/journal.pone.0131422 |issn=1932-6203 |pmc=4511808 |pmid=26200895}}</ref><ref>{{Cite web |title=First evidence of farming in Mideast 23,000 years ago: Evidence of earliest small-scale agricultural cultivation |url=https://www.sciencedaily.com/releases/2015/07/150722144709.htm |access-date=2022-04-23 |website=ScienceDaily |language=en}}</ref> Rice was [[Agriculture in China|domesticated in China]] between 11,500 and 6,200 BC with the earliest known cultivation from 5,700 BC,<ref>{{cite journal |pmid=17898767 |year=2007 |last1=Zong |first1=Y. |last2=When |first2=Z. |last3=Innes |first3=J. B. |last4=Chen |first4=C. |last5=Wang |first5=Z. |last6=Wang |first6=H. |title=Fire and flood management of coastal swamp enabled first rice paddy cultivation in east China |volume=449 |issue=7161 |pages=459–462 |doi=10.1038/nature06135 |journal=Nature |bibcode=2007Natur.449..459Z |s2cid=4426729 }}</ref> followed by [[mung bean|mung]], [[soy]] and [[Azuki bean|azuki]] beans. Sheep were domesticated in [[Mesopotamia]] between 13,000 and 11,000 years ago.<ref>{{cite book |title=Sheep and Goat Science |edition=Fifth |last=Ensminger |first=M. E. |author2=Parker, R. O. |year=1986 |publisher=Interstate Printers and Publishers |isbn=978-0-8134-2464-4}}</ref> Cattle were domesticated from the wild [[aurochs]] in the areas of modern Turkey and Pakistan some 10,500 years ago.<ref name="McTavish">{{cite journal |author=McTavish, E. J. |author2=Decker, J. E. |author3=Schnabel, R.D. |author4=Taylor, J. F. |author5=Hillis, D. M. |year=2013 |title=New World cattle show ancestry from multiple independent domestication events |journal=PNAS |volume=110 |issue=15 |pages=E1398–1406 |doi=10.1073/pnas.1303367110 |pmid=23530234 |pmc=3625352 |bibcode=2013PNAS..110E1398M |doi-access=free }}</ref> [[Domestic pig|Pig production]] emerged in Eurasia, including Europe, East Asia and Southwest Asia,<ref>{{Cite journal |last1=Larson |first1=Greger |last2=Dobney |first2=Keith |author-link2= Keith Dobney |last3=Albarella |first3=Umberto |last4=Fang |first4=Meiying |last5=Matisoo-Smith |first5=Elizabeth |last6=Robins |first6=Judith |last7=Lowden |first7=Stewart |last8=Finlayson |first8=Heather |last9=Brand |first9=Tina |date=11 March 2005 |title=Worldwide Phylogeography of Wild Boar Reveals Multiple Centers of Pig Domestication |journal=Science |volume=307 |issue=5715 |pages=1618–1621 |doi=10.1126/science.1106927 |pmid=15761152|bibcode=2005Sci...307.1618L |s2cid=39923483 }}</ref> where [[wild boar]] were first domesticated about 10,500 years ago.<ref>{{Cite journal |last1=Larson |first1=Greger |last2=Albarella |first2=Umberto |last3=Dobney |first3=Keith |last4=Rowley-Conwy |first4=Peter |last5=Schibler |first5=Jörg |last6=Tresset |first6=Anne |last7=Vigne |first7=Jean-Denis |last8=Edwards |first8=Ceiridwen J. |last9=Schlumbaum |first9=Angela |date=25 September 2007 |title=Ancient DNA, pig domestication, and the spread of the Neolithic into Europe |journal=PNAS |volume=104 |issue=39 |pages=15276–15281 |doi=10.1073/pnas.0703411104 |pmid=17855556 |pmc=1976408 |bibcode=2007PNAS..10415276L |doi-access=free }}</ref> In the [[Andes]] of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, [[coca]], [[llama]]s, [[alpaca]]s, and [[guinea pig]]s. [[Sugarcane]] and some [[List of root vegetables|root vegetables]] were domesticated in [[New Guinea]] around 9,000 years ago. [[Sorghum]] was domesticated in the [[Sahel]] region of Africa by 7,000 years ago. Cotton was domesticated in [[Peru]] by 5,600 years ago,<ref name="Broudy1979">{{cite book |last=Broudy |first=Eric |title=The Book of Looms: A History of the Handloom from Ancient Times to the Present |url={{google books|plainurl=y|id=shN5_-W1RzcC|page=81}} |year=1979 |publisher=UPNE |isbn=978-0-87451-649-4 |page=81 |url-status=live |archive-url=https://web.archive.org/web/20180210232500/{{google books|plainurl=y|id=shN5_-W1RzcC|page=81}} |archive-date=10 February 2018}}</ref> and was independently domesticated in Eurasia. [[Agriculture in Mesoamerica|In Mesoamerica]], wild [[teosinte]] was bred into maize by 6,000 years ago.<ref>Johannessen, S.; Hastorf, C. A. (eds.) ''Corn and Culture in the Prehistoric New World'', Westview Press, Boulder, Colorado.</ref>

In Eurasia, the [[Sumer]]ians started to live in villages from about 8,000 BC, relying on the [[Tigris]] and [[Euphrates]] rivers and a canal system for irrigation. Ploughs appear in [[pictograph]]s around 3,000 BC; seed-ploughs around 2,300 BC. Farmers grew wheat, barley, vegetables such as lentils and onions, and fruits including dates, grapes, and figs.<ref name=BritMus>{{cite web |title=Farming |url=http://www.mesopotamia.co.uk/staff/resources/background/bg08/home.html |publisher=[[British Museum]] |access-date=15 June 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160616222522/http://www.mesopotamia.co.uk/staff/resources/background/bg08/home.html |archive-date=16 June 2016 }}</ref> [[Ancient Egyptian agriculture]] relied on the [[Nile River]] and its seasonal flooding. Farming started in the predynastic period at the end of the [[Paleolithic]], after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as [[flax]] and [[papyrus]].<ref name=Janick>{{cite journal |author=Janick, Jules |title=Ancient Egyptian Agriculture and the Origins of Horticulture |journal=Acta Hort. |volume=583 |pages=23–39 |url=https://www.hort.purdue.edu/newcrop/Hort_306/text/lec06.pdf}}</ref><ref>{{cite book |author=Kees, Herman |title=Ancient Egypt: A Cultural Topography |url=https://archive.org/details/ancientegyptcult0000kees |url-access=registration |publisher=University of Chicago Press |date=1961 |isbn=9780226429144 }}</ref> In [[Agriculture in India|India]], wheat, barley and [[jujube]] were domesticated by 9,000 BC, soon followed by sheep and goats.<ref name=gupta>{{cite journal |author=Gupta, Anil K. |title=Origin of agriculture and domestication of plants and animals linked to early Holocene climate amelioration |url=http://repository.ias.ac.in/21961/1/333.pdf |journal=Current Science |volume=87 |issue=1 |year=2004 |page=59 |jstor=24107979}}</ref> Cattle, sheep and goats were domesticated in [[Mehrgarh]] culture by 8,000–6,000 BC.<ref name=Baber>Baber, Zaheer (1996). ''The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India''. State University of New York Press. 19. {{ISBN|0-7914-2919-9}}.</ref><ref name=harrisandgosden385>Harris, David R. and Gosden, C. (1996). ''The Origins and Spread of Agriculture and Pastoralism in Eurasia: Crops, Fields, Flocks And Herds''. Routledge. p. 385. {{ISBN|1-85728-538-7}}.</ref><ref name=Possehl>Possehl, Gregory L. (1996). ''Mehrgarh'' in ''Oxford Companion to Archaeology'', Ed. Brian Fagan. Oxford University Press.</ref> Cotton was cultivated by the 5th–4th millennium BC.<ref>Stein, Burton (1998). ''A History of India''. Blackwell Publishing. p. 47. {{ISBN|0-631-20546-2}}.</ref> Archeological evidence indicates an animal-drawn [[plough]] from 2,500 BC in the [[Indus Valley Civilisation]].<ref name=lal>{{Cite journal |title=Thematic evolution of ISTRO: transition in scientific issues and research focus from 1955 to 2000 |first=R. |last=Lal |journal=Soil and Tillage Research |volume=61 |issue=1–2 |date=2001 |pages=3–12 |doi=10.1016/S0167-1987(01)00184-2}}</ref>

[[Subsistence farming]] is practiced to satisfy family or local needs alone, with little left over for transport elsewhere. It is intensively practiced in Monsoon Asia and South-East Asia.<ref>{{cite book |author=Waters, Tony |title=The Persistence of Subsistence Agriculture: life beneath the level of the marketplace |publisher=Lexington Books |date=2007}}</ref> An estimated 2.5&nbsp;billion subsistence farmers worked in 2018, cultivating about 60% of the earth's [[arable land]].<ref>{{Cite journal |last=<!--no byline--> |date=7 March 2018 |title=Chinese project offers a brighter farming future |department=Editorial |journal=Nature |volume=555 |issue=7695 |page=141 |doi=10.1038/d41586-018-02742-3 |pmid=29517037 |bibcode=2018Natur.555R.141. |doi-access=free }}</ref>

[[Intensive farming]] is cultivation to maximise productivity, with a low fallow ratio and a high use of inputs (water, fertilizer, pesticide and automation). It is practiced mainly in developed countries.<ref>{{Cite web|url=http://www.britannica.com/eb/article-9042533|archive-url=https://web.archive.org/web/20060705221311/http://www.britannica.com/eb/article-9042533|url-status=dead|title=Encyclopædia Britannica's definition of Intensive Agriculture|archive-date=5 July 2006}}</ref><ref name="bbcFactSheet">{{Cite web|url=http://www.bbc.co.uk/schools/gcsebitesize/biology/livingthingsenvironment/4foodandsustainabilityrev5.shtml|archive-url=https://web.archive.org/web/20070503035007/http://www.bbc.co.uk/schools/gcsebitesize/biology/livingthingsenvironment/4foodandsustainabilityrev5.shtml|url-status=dead|title=BBC School fact sheet on intensive farming|archive-date=3 May 2007}}</ref>

From the twentieth century, intensive agriculture increased productivity. It substituted synthetic fertilizers and pesticides for labour, but caused increased water pollution, and often involved farm subsidies. In recent years there has been a backlash against the [[environmental awareness|environmental effects]] of conventional agriculture, resulting in the [[organic farming|organic]], [[Regenerative agriculture|regenerative]], and [[sustainable agriculture]] movements.<ref name="motherjones1" /><ref>{{cite web |publisher=The World Bank |year=1995 |url=http://econ.worldbank.org/external/default/main?pagePK=64165259&theSitePK=469372&piPK=64165421&menuPK=64166093&entityID=000009265_3970311122936 |title=Overcoming agricultural pollution of water: the challenge of integrating agricultural and environmental policies in the European Union, Volume 1 |access-date=15 April 2013 |author=Scheierling, Susanne M. |url-status=dead |archive-url=https://web.archive.org/web/20130605112426/http://econ.worldbank.org/external/default/main?pagePK=64165259&theSitePK=469372&piPK=64165421&menuPK=64166093&entityID=000009265_3970311122936 |archive-date=5 June 2013}}</ref> One of the major forces behind this movement has been the [[European Union]], which first certified [[organic food]] in 1991 and began reform of its [[Common Agricultural Policy]] (CAP) in 2005 to phase out commodity-linked farm subsidies,<ref>{{cite web |publisher=European Commission |year=2003 |url=http://ec.europa.eu/agriculture/capreform/index_en.htm |title=CAP Reform |access-date=15 April 2013 |url-status=live |archive-url=https://web.archive.org/web/20101017124251/http://ec.europa.eu/agriculture/capreform/index_en.htm |archive-date=17 October 2010}}</ref> also known as [[Decoupling and re-coupling|decoupling]]. The growth of organic farming has renewed research in alternative technologies such as [[integrated pest management]], selective breeding,<ref>{{Cite book |last1=Poincelot |first1=Raymond P. |title=Toward a More Sustainable Agriculture |chapter=Organic Farming |journal=Towards a More Sustainable Agriculture |pages=14–32 |doi=10.1007/978-1-4684-1506-3_2 |year=1986 |isbn=978-1-4684-1508-7 }}</ref> and [[controlled-environment agriculture]].<ref name=":1">{{Cite news |url=http://www.agweek.com/business/agriculture/4527042-cutting-edge-technology-will-change-farming |title=The cutting-edge technology that will change farming |work=Agweek |date=9 November 2018 |access-date=23 November 2018 |archive-url=https://web.archive.org/web/20181117020138/http://www.agweek.com/business/agriculture/4527042-cutting-edge-technology-will-change-farming |archive-date=17 November 2018}}</ref><ref>{{Cite news |author=Charles, Dan |url=https://www.npr.org/sections/thesalt/2017/11/02/561462293/hydroponic-veggies-are-taking-over-organic-and-a-move-to-ban-them-fails |title=Hydroponic Veggies Are Taking Over Organic, And A Move To Ban Them Fails |work=[[NPR]] |date=3 November 2017 |access-date=24 November 2018}}</ref> Recent mainstream technological developments include [[genetically modified food]].<ref>[http://www.bis.gov.uk/files/file15655.pdf GM Science Review First Report] {{webarchive |url=https://web.archive.org/web/20131016100707/http://www.bis.gov.uk/files/file15655.pdf |date=16 October 2013 }}, Prepared by the UK GM Science Review panel (July 2003). Chairman David King, p. 9</ref> Demand for non-food biofuel crops,<ref>{{cite journal |author1=Smith, Kate |author2=Edwards, Rob |date=8 March 2008 |url=http://www.heraldscotland.com/2008-the-year-of-global-food-crisis-1.828546 |title=2008: The year of global food crisis |journal=The Herald |url-status=live |archive-url=https://web.archive.org/web/20130411220739/http://www.heraldscotland.com/2008-the-year-of-global-food-crisis-1.828546 |archive-date=11 April 2013}}</ref> development of former farm lands, rising transportation costs, [[Greenhouse gas emissions from agriculture|climate change]], growing consumer demand in China and India, and [[population growth]],<ref>{{cite journal |url=http://www.csmonitor.com/2008/0118/p08s01-comv.html |title=The global grain bubble |journal=The Christian Science Monitor |date=18 January 2008 |access-date=26 September 2013 |url-status=live |archive-url=https://web.archive.org/web/20091130063759/http://www.csmonitor.com/2008/0118/p08s01-comv.html |archive-date=30 November 2009}}</ref> are threatening [[food security]] in many parts of the world.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/world/7284196.stm |title=The cost of food: Facts and figures |publisher=BBC |date=16 October 2008 |access-date=26 September 2013 |url-status=live |archive-url=https://web.archive.org/web/20090120025945/http://news.bbc.co.uk/1/hi/world/7284196.stm |archive-date=20 January 2009}}</ref><ref>{{cite magazine |author=Walt, Vivienne |date=27 February 2008 |url=http://www.time.com/time/world/article/0,8599,1717572,00.html |title=The World's Growing Food-Price Crisis |magazine=Time |url-status=dead |archive-url=https://web.archive.org/web/20111129211855/http://www.time.com/time/world/article/0,8599,1717572,00.html |archive-date=29 November 2011 }}</ref><ref name="guardian.co.uk">Watts, Jonathan (4 December 2007). [https://www.theguardian.com/world/2007/dec/04/china.business "Riots and hunger feared as demand for grain sends food costs soaring"] {{webarchive|url=https://web.archive.org/web/20130901074034/http://www.theguardian.com/world/2007/dec/04/china.business |date=1 September 2013 }}, ''The Guardian'' (London).</ref><ref name="timesonline.co.uk">Mortished, Carl (7 March 2008).[http://www.timesonline.co.uk/tol/news/environment/article3500975.ece "Already we have riots, hoarding, panic: the sign of things to come?"] {{webarchive|url=https://web.archive.org/web/20110814134028/http://www.timesonline.co.uk/tol/news/environment/article3500975.ece |date=14 August 2011}}, ''The Times'' (London).</ref><ref name="ReferenceA">Borger, Julian (26 February 2008). [https://www.theguardian.com/environment/2008/feb/26/food.unitednations "Feed the world? We are fighting a losing battle, UN admits"] {{webarchive|url=https://web.archive.org/web/20161225150554/https://www.theguardian.com/environment/2008/feb/26/food.unitednations |date=25 December 2016}}, ''The Guardian'' (London).</ref> The [[International Fund for Agricultural Development]] posits that an increase in [[smallholding|smallholder agriculture]] may be part of the solution to concerns about [[food prices]] and overall food security, given the favorable experience of Vietnam.<ref>{{cite web |url=http://www.ifad.org/operations/food/farmer.htm |title=Food prices: smallholder farmers can be part of the solution |publisher=International Fund for Agricultural Development |access-date=24 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130505224355/http://www.ifad.org/operations/food/farmer.htm |archive-date=5 May 2013 }}</ref> [[soil retrogression and degradation|Soil degradation]] and diseases such as [[stem rust]] are major concerns globally;<ref>{{cite web |url=http://www.fao.org/agriculture/crops/rust/stem/rust-report/stem-ug99racettksk/en/ |title=Wheat Stem Rust – UG99 (Race TTKSK)|publisher=FAO|access-date=6 January 2014|url-status=live|archive-url=https://web.archive.org/web/20140107064545/http://www.fao.org/agriculture/crops/rust/stem/rust-report/stem-ug99racettksk/en/|archive-date=7 January 2014}}</ref> approximately 40% of the world's agricultural land is seriously degraded.<ref>Sample, Ian (31 August 2007). [https://www.theguardian.com/environment/2007/aug/31/climatechange.food "Global food crisis looms as climate change and population growth strip fertile land"] {{webarchive |url=https://web.archive.org/web/20160429094959/https://www.theguardian.com/environment/2007/aug/31/climatechange.food |date=29 April 2016}}, ''The Guardian'' (London).</ref><ref>{{cite news |url=http://news.mongabay.com/2006/1214-unu.html |title=Africa may be able to feed only 25% of its population by 2025 |archive-url=https://web.archive.org/web/20111127175559/http://news.mongabay.com/2006/1214-unu.html |archive-date=27 November 2011 |work=[[Mongabay]] |date=14 December 2006 |access-date=15 July 2016 |url-status=dead }}</ref> By 2015, the agricultural output of China was the largest in the world, followed by the European Union, India and the United States.<ref name=UNCTAD2017 /> Economists measure the [[total factor productivity]] of agriculture and by this measure agriculture in the United States is roughly 1.7 times more productive than it was in 1948.<ref>{{cite web |publisher=USDA Economic Research Service |url=http://www.ers.usda.gov/data/agproductivity/ |title=Agricultural Productivity in the United States |date=5 July 2012 |access-date=22 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130201021133/http://www.ers.usda.gov/Data/AgProductivity/ |archive-date=1 February 2013 }}</ref>

Livestock production systems can be defined based on feed source, as grassland-based, mixed, and landless.<ref name="FAO lps">{{cite web |author1=Sere, C. |author2=Steinfeld, H. |author3=Groeneweld, J. |year=1995 |url=http://www.fao.org/WAIRDOCS/LEAD/X6101E/x6101e00.htm#Contents|title=Description of Systems in World Livestock Systems – Current status issues and trends |publisher=U.N. Food and Agriculture Organization |access-date=8 September 2013 |url-status=live |archive-url=https://web.archive.org/web/20121026004040/http://www.fao.org/WAIRDOCS/LEAD/X6101E/X6101E00.HTM#Contents |archive-date=26 October 2012 }}</ref> {{as of|2010}}, 30% of Earth's ice- and water-free area was used for producing livestock, with the sector employing approximately 1.3&nbsp;billion people. Between the 1960s and the 2000s, there was a significant increase in livestock production, both by numbers and by carcass weight, especially among beef, pigs and chickens, the latter of which had production increased by almost a factor of 10. Non-meat animals, such as milk cows and egg-producing chickens, also showed significant production increases. Global cattle, sheep and goat populations are expected to continue to increase sharply through 2050.<ref name=LP>{{cite journal |title=Livestock production: recent trends, future prospects |author=Thornton, Philip K. |doi=10.1098/rstb.2010.0134 |pmid=20713389 |journal=Philosophical Transactions of the Royal Society B |date=27 September 2010 |volume=365 |issue=1554 |pages=2853–2867 |doi-access=free |pmc=2935116 }}</ref> [[Aquaculture]] or fish farming, the production of fish for human consumption in confined operations, is one of the fastest growing sectors of food production, growing at an average of 9% a year between 1975 and 2007.<ref>{{cite magazine |url=http://content.time.com/time/health/article/0,8599,1663604,00.html |title=Fish Farming's Growing Dangers |magazine=Time |author=Stier, Ken |date=19 September 2007|url-status=live |archive-url=https://web.archive.org/web/20130907071708/http://content.time.com/time/health/article/0,8599,1663604,00.html |archive-date=7 September 2013 }}</ref>

Grassland based livestock production relies upon plant material such as [[shrubland]], [[rangeland]], and [[managed intensive rotational grazing|pastures]] for feeding [[ruminant]] animals. Outside nutrient inputs may be used, however manure is returned directly to the grassland as a major nutrient source. This system is particularly important in areas where crop production is not feasible because of climate or soil, representing 30–40&nbsp;million pastoralists.<ref name="CS" /> Mixed production systems use grassland, [[fodder]] crops and grain feed crops as feed for ruminant and monogastric (one stomach; mainly chickens and pigs) livestock. Manure is typically recycled in mixed systems as a fertilizer for crops.<ref name="FAO lps" />

Agriculture imposes multiple external costs upon society through effects such as pesticide damage to nature (especially herbicides and insecticides), nutrient runoff, excessive water usage, and loss of natural environment. A 2000 assessment of agriculture in the UK determined total external costs for 1996 of £2,343&nbsp;million, or £208 per hectare.<ref name=Pretty2000>{{cite journal |last1=Pretty |year=2000 |title=An assessment of the total external costs of UK agriculture |journal=Agricultural Systems |volume=65 |issue=2 |pages=113–136 |doi=10.1016/S0308-521X(00)00031-7 |first1=J. |display-authors=1 |last2=Brett |first2=C. |last3=Gee |first3=D. |last4=Hine |first4=R. E. |last5=Mason |first5=C. F. |last6=Morison |first6=J. I. L. |last7=Raven |first7=H. |last8=Rayment |first8=M. D. |last9=Van Der Bijl |first9=G. |url=https://www.researchgate.net/publication/222549141 |url-status=live |archive-url=https://web.archive.org/web/20170113233847/https://www.researchgate.net/publication/222549141 |archive-date=13 January 2017}}</ref> A 2005 analysis of these costs in the US concluded that cropland imposes approximately $5 to $16&nbsp;billion ($30 to $96 per hectare), while livestock production imposes $714&nbsp;million.<ref name=Tegtmeier2005>{{cite journal |last1=Tegtmeier |first1=E. M. |last2=Duffy |first2=M. |year=2005 |title=External Costs of Agricultural Production in the United States |journal=The Earthscan Reader in Sustainable Agriculture |url=http://www.organicvalley.coop/fileadmin/pdf/ag_costs_IJAS2004.pdf |url-status=live |archive-url=https://web.archive.org/web/20090205134016/http://www.organicvalley.coop/fileadmin/pdf/ag_costs_IJAS2004.pdf |archive-date=5 February 2009}}</ref> Both studies, which focused solely on the fiscal impacts, concluded that more should be done to internalize external costs. Neither included subsidies in their analysis, but they noted that subsidies also influence the cost of agriculture to society.<ref name=Pretty2000 /><ref name=Tegtmeier2005 />

Land transformation, the use of land to yield goods and services, is the most substantial way humans alter the Earth's ecosystems, and is the driving force causing [[biodiversity loss]]. Estimates of the amount of land transformed by humans vary from 39 to 50%.<ref name="Vitousek">{{cite journal |author1=Vitousek, P. M. |author2=Mooney, H. A. |author3=Lubchenco, J. |author4=Melillo, J. M. |year=1997 |title=Human Domination of Earth's Ecosystems |journal=Science |volume=277 |pages=494–499 |doi=10.1126/science.277.5325.494 |issue=5325 |citeseerx=10.1.1.318.6529 }}</ref> Land degradation, the long-term decline in ecosystem function and productivity, is estimated to be occurring on 24% of land worldwide, with cropland overrepresented.<ref name="FAO GLADA">{{cite web|author=Bai, Z.G. |author2=D.L. Dent |author3=L. Olsson |author4=M.E. Schaepman |name-list-style=amp |date=November 2008 |title=Global assessment of land degradation and improvement: 1. identification by remote sensing |publisher=FAO/ISRIC |url=http://www.isric.org/isric/webdocs/docs/Report%202008_01_GLADA%20international_REV_Nov%202008.pdf |access-date=24 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131213041558/http://www.isric.org/isric/webdocs/docs/Report%202008_01_GLADA%20international_REV_Nov%202008.pdf |archive-date=13 December 2013 }}</ref> Land management is the driving factor behind degradation; 1.5&nbsp;billion people rely upon the degrading land. Degradation can be through deforestation, [[desertification]], [[soil erosion]], mineral depletion, [[soil acidification|acidification]], or [[Soil salinity|salinization]].<ref name="CS" />

[[Eutrophication]], excessive nutrient enrichment in [[aquatic ecosystem]]s resulting in [[algal bloom]]s and [[anoxic waters|anoxia]], leads to [[fish kill]]s, loss of biodiversity, and renders water unfit for drinking and other industrial uses. Excessive fertilization and manure application to cropland, as well as high livestock stocking densities cause nutrient (mainly [[nitrogen]] and [[phosphorus]]) [[surface runoff|runoff]] and [[leaching (agriculture)|leaching]] from agricultural land. These nutrients are major [[nonpoint source pollution|nonpoint pollutants]] contributing to [[eutrophication]] of aquatic ecosystems and pollution of groundwater, with harmful effects on human populations.<ref name="Eutr">{{cite journal |author=Carpenter, S. R. |author2=Caraco, N. F. |author3=Correll, D. L. |author4=Howarth, R. W. |author5=Sharpley, A. N. |author6=Smith, V. H. |year=1998 |title=Nonpoint Pollution of Surface Waters with Phosphorus and Nitrogen |journal=Ecological Applications |volume=8 |pages=559–568 |doi=10.1890/1051-0761(1998)008[0559:NPOSWW]2.0.CO;2 |issue=3 |hdl=1808/16724 |hdl-access=free}}</ref> Fertilisers also reduce terrestrial biodiversity by increasing competition for light, favouring those species that are able to benefit from the added nutrients.<ref name="Hautier Niklaus Hector">{{cite journal |last1=Hautier |first1=Y. |last2=Niklaus |first2=P. A. |last3=Hector |first3=A. |title=Competition for Light Causes Plant Biodiversity Loss After Eutrophication |journal=Science |volume=324 |issue=5927 |date=2009 |doi=10.1126/science.1169640 |pmid=19407202 |pages=636–638|bibcode=2009Sci...324..636H |s2cid=21091204 |url=https://www.zora.uzh.ch/id/eprint/18666/2/Hautier_2009.pdf |type=Submitted manuscript }}</ref>

Pesticide use has increased since 1950 to 2.5{{nbsp}}million short tons annually worldwide, yet crop loss from pests has remained relatively constant.<ref name="Pimentel pesticide">{{cite web |author1=Pimentel, D. |author2=Culliney, T. W. |author3=Bashore, T. |year=1996 |url=http://ipmworld.umn.edu/chapters/pimentel.htm |archive-url=https://web.archive.org/web/19990218073023/http://ipmworld.umn.edu/chapters/pimentel.htm |url-status=dead |archive-date=18 February 1999 |title=Public health risks associated with pesticides and natural toxins in foods |website=Radcliffe's IPM World Textbook |access-date=7 May 2013}}</ref> The World Health Organization estimated in 1992 that three million pesticide poisonings occur annually, causing 220,000 deaths.<ref name="WHO">''Our planet, our health: Report of the WHO commission on health and environment''. Geneva: [[World Health Organization]] (1992).</ref> Pesticides select for [[pesticide resistance]] in the pest population, leading to a condition termed the "pesticide treadmill" in which pest resistance warrants the development of a new pesticide.<ref name="CS Pest">"Strategies for Pest Control", pp. 355–383 in [[#Chrispeels|Chrispeels]]</ref>

{{Main|Plastic pollution}}

The total amount of plastics used in agriculture is difficult to quantify. A 2012 study reported that almost 6.5 million tonnes per year were consumed globally while a later study estimated that global demand in 2015 was between 7.3 million and 9 million tonnes. Widespread use of plastic mulch and lack of systematic collection and management have led to the generation of large amounts of mulch residue.Weathering and degradation eventually cause the mulch to fragment. These fragments and larger pieces of plastic accumulate in soil. Mulch residue has been measured at levels of 50 to 260&nbsp;kg per hectare in topsoil in areas where the mulch has been used for more than 10 years, which confirms that mulching is a major source of both microplastic and macroplastic contamination of soil.<ref name=":0" />

* {{NYTtopic|subjects/a/agriculture}}

* {{Guardian topic |science/agriculture}}

 

[[Category:Agriculture|Agriculture]]