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Forests account for 75% of the [[gross primary production]] of the Earth's [[biosphere]], and contain 80% of the Earth's plant [[biomass]]. [[Primary_production#Gross_primary_production_and_net_primary_production|Net primary production]] is estimated at 21.9 [[gigatonne]]s of biomass per year for [[tropical forest]]s, 8.1 for [[temperate forest]]s, and 2.6 for [[boreal forest]]s.<ref name="yude" />
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
[[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|date=6 January 2022 }}</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"/>
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