[[File:Adirondacks in May 2008.jpg|thumb|300px|The [[Adirondack Mountains]] of [[Upstate New York]] form the southernmost part of the [[Eastern forest-boreal transition]] [[ecoregion]].]]
A '''forest''' is an area[[ecosystem]] ofcharacterized by land dominated by [[tree]]s.<ref>{{cite web |url=http://dictionary.reference.com/browse/forest |title=Forest |website=Dictionary.com |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141019171930/http://dictionary.reference.com/browse/forest |archive-date=19 October 2014}}</ref> Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function.<ref>{{cite web |url=http://www.efi.int/files/attachments/publications/ir_06.pdf |title=Compilation of Forestry Terms and Definitions |first1=Andreas |last1=Schuck |first2=Risto |last2=Päivinen |first3=Tuomo |last3=Hytönend |first4=Brita |last4=Pajari |publisher=[[European Forest Institute]] |location=Joensuu, Finland |year=2002 |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20150605064820/http://www.efi.int/files/attachments/publications/ir_06.pdf |archive-date=5 June 2015}}</ref><ref name="cbd">{{cite web |url=http://www.cbd.int/forest/definitions.shtml |title=Definitions: Indicative definitions taken from the Report of the ad hoc technical expert group on forest biological diversity |date=30 November 2006 |publisher=[[Convention on Biological Diversity]] |access-date=16 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141219030427/http://www.cbd.int/forest/definitions.shtml |archive-date=19 December 2014}}</ref><ref name="unep">{{cite web |url = http://www.unep.org/vitalforest/Report/VFG-01-Forest-definition-and-extent.pdf |archive-url=https://web.archive.org/web/20100726140947/http://www.unep.org/vitalforest/Report/VFG-01-Forest-definition-and-extent.pdf |url-status=dead |archive-date=26 July 2010 |title=Forest definition and extent |date=27 January 2010 |publisher=United Nations Environment Programme |access-date=16 November 2014}}</ref> The United Nations' [[Food and Agriculture Organization]] (FAO) defines a forest as, "Land spanning more than 0.5 hectares with trees higher than 5 meters and a [[Canopy (biology)|canopy]] cover of more than 10 percent, or trees able to reach these thresholds ''in situ''. It does not include land that is predominantly under agricultural or urban use."<ref>{{Cite book|url=http://www.fao.org/3/I8661EN/i8661en.pdf |archive-url=https://web.archive.org/web/20190809045851/http://www.fao.org/3/I8661EN/i8661en.pdf |archive-date=9 August 2019 |url-status=live |title=Global Forest Resources Assessment 2020 – Terms and definitions |publisher=[[Food and Agriculture Organization]] |year=2018 |location=Rome}}</ref> Using this definition, ''[[Global Forest Resources Assessment (FRA)|Global Forest Resources Assessment]] 2020'' (FRA 2020) found that forests covered {{convert|4.06|e9ha|e9acre e6sqkm e6sqmi|abbr=off}}, or approximately 31 percent of the world's land area in 2020.<ref>{{Cite book |url=https://doi.org/10.4060/ca8985en |title=The State of the World's Forests 2020. In brief – Forests, biodiversity and people |publisher=[[Food and Agriculture Organization|FAO]] & UNEP |year=2020 |isbn=978-92-5-132707-4 |location=Rome |doi=10.4060/ca8985en |s2cid=241416114}}</ref>
Forests are the largest terrestrial [[ecosystem]] of Earth by area, and are found around the globe.<ref name=yude>{{cite journal |title=The Structure, Distribution, and Biomass of the World's Forests |first1=Yude |last1=Pan |first2=Richard A. |last2=Birdsey |first3=Oliver L. |last3=Phillips |first4=Robert B. |last4=Jackson |journal=Annu. Rev. Ecol. Evol. Syst. |year=2013 |volume=44 |pages=593–62 |url=http://www.nrs.fs.fed.us/pubs/jrnl/2013/nrs_2013_pan_001.pdf |doi=10.1146/annurev-ecolsys-110512-135914 |url-status=live |archive-url=https://web.archive.org/web/20160807012240/http://www.nrs.fs.fed.us/pubs/jrnl/2013/nrs_2013_pan_001.pdf |archive-date=7 August 2016}}</ref> 45 percent of forest land is in the [[Tropical forest|tropical latitudes]]. The next largest share of forests are found in [[subarctic climate]]s, followed by [[Temperate rainforest|temperate]], and [[subtropic]]al zones<ref name="auto">{{Cite book |url=https://doi.org/10.4060/ca8985en |title=The State of the World's Forests 2020. In brief – Forests, biodiversity and people |publisher=[[Food and Agriculture Organization|FAO]] & UNEP |year=2020 |isbn=978-92-5-132707-4 |location=Rome, Italy |doi=10.4060/ca8985en |s2cid=241416114}}</ref>