Forest

A forest is an <a href="/facts/Ecosystem/kVE8mSmR">ecosystem</a> characterized by a dense <a href="/facts/Ecological_community/HnQwVCdz">community</a> of <a href="/facts/Tree/HVVn3srN">trees</a>. 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. The United Nations' <a href="/facts/Food_and_Agriculture_Organization/13WV8JJK">Food and Agriculture Organization</a> (FAO) defines a forest as, "Land spanning more than 0.5 hectares with trees higher than 5 meters and a <a href="/facts/Canopy_(biology)/P1C0uxKl">canopy</a> cover of more than 10 percent, or trees able to reach these thresholds <a href="/facts/In_situ/YolKlaCC">in situ</a>. It does not include land that is predominantly under agricultural or urban use." Using this definition, <a href="/facts/Global_Forest_Resources_Assessment_(FRA)/sYfo1rMT">Global Forest Resources Assessment 2020</a> found that forests covered 4.06 billion hectares (10.0 billion acres; 40.6 million square kilometres; 15.7 million square miles), or approximately 31 percent of the world's land area in 2020.
Forests are the largest <a href="/facts/Terrestrial_ecosystem/CsE4XjgP">terrestrial ecosystems</a> of <a href="/facts/Earth/HLLmDfj0">Earth</a> by area, and are found around the globe. 45 percent of forest land is in the <a href="/facts/Tropical_forest/dyjPSoGS">tropical latitudes</a>. The next largest share of forests are found in <a href="/facts/Subarctic_climate/xW83IXdL">subarctic climates</a>, followed by <a href="/facts/Temperate_rainforest/8BMvlVUN">temperate</a>, and <a href="/facts/Subtropic/gK0KyFUD">subtropical</a> zones.
Forests account for 75% of the <a href="/facts/Gross_primary_production/14RzcF5E">gross primary production</a> of the Earth's <a href="/facts/Biosphere/P1ltA4sb">biosphere</a>, and contain 80% of the Earth's plant <a href="/facts/Biomass/4VHjaya3">biomass</a>. <a href="/facts/Primary_production/14RzcF5E">Net primary production</a> is estimated at 21.9 <a href="/facts/Gigatonne/gMymLmWv">gigatonnes</a> of biomass per year for <a href="/facts/Tropical_forest/dyjPSoGS">tropical forests</a>, 8.1 for <a href="/facts/Temperate_forest/aw95pQVu">temperate forests</a>, and 2.6 for <a href="/facts/Boreal_forest/xjkPQRJs">boreal forests</a>.
Forests form distinctly different <a href="/facts/Biome/cl4X36GB">biomes</a> at different latitudes and elevations, and with different precipitation and <a href="/facts/Evapotranspiration/q1h1G3XI">evapotranspiration</a> rates. These biomes include boreal forests in subarctic climates, <a href="/facts/Tropical_and_subtropical_moist_broadleaf_forests/yR0TXBHb">tropical moist forests</a> and <a href="/facts/Tropical_and_subtropical_dry_broadleaf_forests/o88ufPT5">tropical dry forests</a> around the <a href="/facts/Tropics/Iv1es8Ih">Equator</a>, and <a href="/facts/Temperate_forest/aw95pQVu">temperate forests</a> at the <a href="/facts/Middle_latitudes/spJe2FNR">middle latitudes</a>. Forests form in areas of the Earth with high rainfall, while drier conditions produce a transition to <a href="/facts/Savanna/M0tPdd1l">savanna</a>. 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. Research conducted in the <a href="/facts/Amazon_rainforest/MGVatclX">Amazon rainforest</a> 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 two to three months earlier than the climate would otherwise allow. <a href="/facts/Deforestation/L1TNhN9p">Deforestation</a> in the Amazon and anthropogenic <a href="/facts/Climate_change/rEN4BDE7">climate change</a> hold the potential to interfere with this process, causing the forest to pass a threshold where it transitions into savanna.
Deforestation threatens many forest ecosystems. Deforestation occurs when humans remove trees from a forested area by cutting or burning, either to harvest <a href="/facts/Timber/jJfdSlJ6">timber</a> 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: <a href="/facts/Wood/z13NpHPl">wood</a>, <a href="/facts/Beef/yAvkT7Nq">beef</a>, <a href="/facts/Soy/reNwxvo2">soy</a>, and <a href="/facts/Palm_oil/n8zHXqoG">palm oil</a>. Over the past 2,000 years, the area of land covered by forest in <a href="/facts/Europe/DTAtrKfh">Europe</a> has been reduced from 80% to 34%. Large areas of forest have also been cleared in <a href="/facts/China/lTjIXY5p">China</a> and in the eastern <a href="/facts/United_States/P0sCdLe5">United States</a>, in which only 0.1% of land was left undisturbed. 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 1 million hectares (2.5 million acres). The remaining 20 percent is located in more than 34 million patches around the world – the vast majority less than 1,000 hectares (2,500 acres) in size.
Human society and forests can affect one another positively or negatively. Forests provide <a href="/facts/Ecosystem_services/Fm4owYGV">ecosystem services</a> to humans and serve as tourist attractions. Forests can also affect people's health. Human activities, including unsustainable use of forest resources, can negatively affect forest ecosystems.

Forest open-in-new

Forest