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Adding more info about the relationship between forests and climate. I removed the sentence stating the countries where the most forest is found, since the countries mentioned were just the five largest countries by land area, and because of this the statement didn't seem particularly illustrative of anything about forests (other than the obvious connection between forest land area and land area)
More summary on deforestation and made the section under definitions clearer and easier to read
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Forests form distinctly different [[biome]]s at different latitudes and elevations, and with different precipitation and [[evapotranspiration]] rates. <ref>{{Cite book|last=Holdridge |first=L.R. |url=http://reddcr.go.cr/sites/default/files/centro-de-documentacion/holdridge_1966_-_life_zone_ecology.pdf |archive-url=https://web.archive.org/web/20161005035018/http://reddcr.go.cr/sites/default/files/centro-de-documentacion/holdridge_1966_-_life_zone_ecology.pdf |archive-date=5 October 2016 |url-status=live |title=Life zone ecology |publisher=Tropical Science Center |location=San Jose, Costa Rica}}</ref> These biomes include [[boreal]] forests in subarctic climates, [[tropical and subtropical moist broadleaf forests|tropical moist forests]] and [[tropical and subtropical dry broadleaf forests|tropical dry forests]] around the [[tropics|Equator]], and [[temperate forest]]s at the [[middle latitudes]]. Forests form in areas of the Earth with high rainfall, while drier conditions produce a transition to [[savanna]]. However, in areas with intermediate rainfall levels, forest transitions to savanna rapidly when the percentage of land that is covered by trees drops below 40 to 45 percent.<ref>{{cite web |last1=Edwards |first1=Lin |title=Forest and savanna can switch quickly |url=https://phys.org/news/2011-10-forest-savanna-quickly.html |website=Phys.org}}</ref> Research conducted in the [[Amazon rainforest]] shows that trees can alter rainfall rates across a region, releasing water from their leaves in anticipation of seasonal rains to trigger the wet season early. Because of this, seasonal rainfall in the Amazon begins 2 to 3 months earlier than the climate would otherwise allow.<ref>{{cite web |last1=Rasmussen |first1=Carol |title=New study shows the Amazon makes its own rainy season |url=https://climate.nasa.gov/news/2608/new-study-shows-the-amazon-makes-its-own-rainy-season/ |website=nasa.gov}}</ref><ref>{{cite web |last1=Loomis |first1=Ilima |title=Trees in the Amazon make their own rain |url=https://www.science.org/content/article/trees-amazon-make-their-own-rain}}</ref> [[Deforestation]] in the Amazon and anthropogenic [[climate change]] hold the potential to interfere with this process, causing the forest to pass a threshold where it transitions into savanna.<ref>{{cite web |last1=Kimbrough |first1=Liz |title=More droughts are coming, and the Amazon can't keep up: Study |url=https://news.mongabay.com/2022/09/more-droughts-are-coming-and-the-amazon-isnt-ready-study/ |website=Mongabay}}</ref>
 
[[Deforestation]] threatens many forest ecosystems. Deforestation occurs when humans remove trees from a forested area by cutting or burning, either to harvest [[timber]] or to make way for farming. Most deforestation today occurs in tropical forests. The vast majority of this deforestation is because of the production of four commodities: [[wood]], [[beef]], [[soy]], and [[palm oil]].<ref>{{cite web |last1=Derouin |first1=Sarah |title=Deforestation: facts, causes & effects |url=https://www.livescience.com/27692-deforestation.html |website=Live Science}}</ref> Over the past 2,000 years, the area of land covered by forest in [[Europe]] has been reduced from 80% to 34%. Large areas of forest have also been cleared in [[China]] and in the eastern [[United States]]<ref>{{cite web |title=Deforestation |url=https://education.nationalgeographic.org/resource/deforestation/ |publisher=National Geographic}}</ref>, in which only 0.1% of land was left undisturbed.<ref>{{cite web |title=Eastern Deciduous Forest (U.S. National Park Service) |url=https://www.nps.gov/im/ncrn/eastern-deciduous-forest.htm |website=nps.gov}}</ref> Almost half of Earth's forest area (49 percent) is relatively intact, while 9 percent is found in fragments with little or no connectivity. Tropical rainforests and boreal coniferous forests are the least fragmented, whereas subtropical dry forests and temperate oceanic forests are among the most fragmented. Roughly 80 percent of the world's forest area is found in patches larger than {{convert|1|e6ha|abbr=off}}. The remaining 20 percent is located in more than 34 million patches around the world – the vast majority less than {{convert|1000|ha}} in size.<ref name="auto"/>
 
Human society and forests influencecan eachaffect otherone inanother bothpositively positiveor and negative waysnegatively.<ref>{{cite book |chapter=Global Societies and Forest Legacies Creating Today's Forest Landscapes |pages=30–59 |title=Forests and Society: Sustainability and Life Cycles of Forests in Human Landscapes |editor-last=Vogt |editor-first=Kristina A |year=2007 |publisher=CABI |isbn=978-1-84593-098-1}}</ref> Forests provide [[ecosystem services]] to humans and serve as tourist attractions. Forests can also affect people's health.<!--Specific statements supported by refs in "Relationship to human society" section--> Human activities, including unsustainable use of forest resources, can negatively affect forest ecosystems.<!--See same section for refs--><ref>{{Cite web|date=7 February 2019 |title=Deforestation and Its Effect on the Planet |url=https://www.nationalgeographic.com/environment/article/deforestation |access-date=21 July 2021 |website=[[National Geographic]] Environment |language=en}}</ref>
 
== DefinitionDefinitions ==
[[File:Gate in the forest - geograph.org.uk - 1726119.jpg|thumb|Forest in the [[Scottish Highlands]] ]]
 
Although the word ''forest'' is commonly used, there is no universally recognised precise definition, with more than 800 definitions of forest used around the world.<ref name="unep"/> Although a forest is usually defined by the presence of trees, under many definitions an area completely lacking trees may still be considered a forest if it grew trees in the past, will grow trees in the future,<ref name="ap862">{{cite web |url=http://www.fao.org/docrep/017/ap862e/ap862e00.pdf |title=Forest Resources Assessment Working Paper 180 |first1=Kenneth |last1=MacDicken |publisher=[[Food and Agriculture Organization]] of the United Nations Forestry Department |location=Rome |date=15 March 2013 |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20150924131113/http://www.fao.org/docrep/017/ap862e/ap862e00.pdf |archive-date=24 September 2015}}</ref> or was legally designated as a forest regardless of vegetation type.<ref name="ipcc">{{cite web |url=http://www.ipcc.ch/ipccreports/sres/land_use/index.php?idp=46|title=Land Use, Land-Use Change and Forestry |editor1-first=Robert T. |editor1-last=Watson |editor2-first=David J. |editor2-last=Verardo |editor3-first=Ian R. |editor3-last=Noble |editor4-first=Bert |editor4-last=Bolin |editor5-first=N.H. |editor5-last=Ravindranath |editor6-first=David J. |editor6-last=Dokken |publisher=[[Intergovernmental Panel on Climate Change]] |year=2000 |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141129020202/http://www.ipcc.ch/ipccreports/sres/land_use/index.php?idp=46 |archive-date=29 November 2014}}</ref><ref>{{cite web |url=http://www.forestfacts.org/l_3/forests_1.htm#1p1 |title=Facts on Forests and Forestry |first1=Nicholas |last1=Menzies |first2=Elisabeth |last2=Grinspoon |publisher= ForestFacts.org, a subsidiary of GreenFacts.org |date=22 October 2007 |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20150508030720/http://www.forestfacts.org/l_3/forests_1.htm#1p1 |archive-date=8 May 2015}}</ref>
 
There are three broad categories of definitions of forest in use: administrative, [[land use]], and land cover.<ref name="ipcc"/> Administrative definitions are based primarily upon the legal designations of land, and commonlymay bearnot littlereflect relationshipthe totype itsof vegetation: land that isgrows legallyupon designatedthe asland; aan forestarea iscan definedbe aslegally suchdesignated "forest" even if no trees are growinggrow on it.<ref name="ipcc"/> Land-use definitions are based on the primary purpose that the land serves. For example, a forest may be defined as any land that is used primarily for production of timber. Under such a land-use definition, clearedany roadsarea orused infrastructureprimarily withinfor anharvesting areatimber, used for forestry—orincluding areas that have been cleared by harvesting, disease, fire, or fire—arefor the construction of roads and infrastructure, are still considereddefined as forests, even if they contain no trees. Land-cover definitions define forests based upon the type and density of vegetation growing on the land. Such definitions typically define a forest as an area growing trees above some threshold. These thresholds are typically the number of trees per area (density), the area of ground under the [[tree canopy]] (canopy cover), or the sectionarea of the land that is occupied by the cross-section of tree trunks (basal area) meeting a particular threshold.<ref name="ipcc"/> UnderThis such land-cover definitions, an areatype of landdefinition candepends onlyupon bethe knownpresence as forest if it is growingof trees. Areas that failsufficient to meet the land-coverthreshold, definitionor mayat beleast still included whileof immature trees are present that are expected to meet the definitionthreshold atonce they maturitymature.<ref name="ipcc"/>
 
Under land-usecover definitions, there is considerable variation on where the cutoff points are between a forest, [[woodland]], and [[savanna]]. Under some definitions, to be considered a forest requires very high levels of tree canopy cover, from 60% to 100%,<ref>{{cite web |url=http://www.museum.state.il.us/muslink/forest/htmls/intro_def.html |title=Introduction: Definition of a Forest |publisher=MuseumLink Illinois |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141029231145/http://www.museum.state.il.us/muslink/forest/htmls/intro_def.html |archive-date=29 October 2014}}</ref> which excludes woodlands and savannas, which have a lower [[crown closure|canopy cover]]. Other definitions consider savannas to be a type of forest, and include all areas with tree canopies over 10%.<ref name="ap862"/>
 
Some areas covered with trees are legally defined as agricultural areas, e.g.for example [[Norway spruce]] plantations, under Austrian forest law, when the trees are being grown as Christmas trees and are below a certain height.
 
== Etymology ==
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