Global InformationForest information
A forest is an ecosystem characterized by a dense community of trees.[1] 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.[2][3][4] 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 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."[5] Using this definition, Global Forest Resources Assessment 2020 (FRA 2020) 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.[6]
Forests are the largest terrestrial ecosystems of Earth by area, and are found around the globe.[7] 45 percent of forest land is in the tropical latitudes. The next largest share of forests are found in subarctic climates, followed by temperate, and subtropical zones.[8]
Forests account for 75% of the gross primary production of the Earth's biosphere, and contain 80% of the Earth's plant biomass. Net primary production is estimated at 21.9 gigatonnes of biomass per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.[7]
Forests form distinctly different biomes at different latitudes and elevations, and with different precipitation and evapotranspiration rates.[9] These biomes include boreal forests in subarctic climates, tropical moist forests and tropical dry forests around the Equator, and temperate forests 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.[10] 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 two to three months earlier than the climate would otherwise allow.[11][12] 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.[13]
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.[14] 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,[15] in which only 0.1% of land was left undisturbed.[16] 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.[8]
Human society and forests can affect one another positively or negatively.[17] Forests provide ecosystem services 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.[18]
- ^ "Forest". Dictionary.com. Archived from the original on 19 October 2014. Retrieved 16 November 2014.
- ^ Schuck, Andreas; Päivinen, Risto; Hytönend, Tuomo; Pajari, Brita (2002). "Compilation of Forestry Terms and Definitions" (PDF). Joensuu, Finland: European Forest Institute. Archived (PDF) from the original on 5 June 2015. Retrieved 16 November 2014.
- ^ "Definitions: Indicative definitions taken from the Report of the ad hoc technical expert group on forest biological diversity". Convention on Biological Diversity. 30 November 2006. Archived from the original on 19 December 2014. Retrieved 16 November 2014.
- ^ "Forest definition and extent" (PDF). United Nations Environment Programme. 27 January 2010. Archived from the original (PDF) on 26 July 2010. Retrieved 16 November 2014.
- ^ Global Forest Resources Assessment 2020 – Terms and definitions (PDF). Rome: Food and Agriculture Organization. 2018. Archived (PDF) from the original on 9 August 2019.
- ^ The State of the World's Forests 2020. In brief – Forests, biodiversity and people. Rome: FAO & UNEP. 2020. doi:10.4060/ca8985en. ISBN 978-92-5-132707-4. S2CID 241416114.
- ^ a b Pan, Yude; Birdsey, Richard A.; Phillips, Oliver L.; Jackson, Robert B. (2013). "The Structure, Distribution, and Biomass of the World's Forests" (PDF). Annu. Rev. Ecol. Evol. Syst. 44: 593–62. doi:10.1146/annurev-ecolsys-110512-135914. Archived (PDF) from the original on 7 August 2016.
- ^ a b The State of the World's Forests 2020. In brief – Forests, biodiversity and people. Rome, Italy: FAO & UNEP. 2020. doi:10.4060/ca8985en. ISBN 978-92-5-132707-4. S2CID 241416114.
- ^ Holdridge, L.R. Life zone ecology (PDF). San Jose, Costa Rica: Tropical Science Center. Archived (PDF) from the original on 5 October 2016.
- ^ Edwards, Lin. "Forest and savanna can switch quickly". Phys.org.
- ^ Rasmussen, Carol. "New study shows the Amazon makes its own rainy season". nasa.gov.
- ^ Loomis, Ilima. "Trees in the Amazon make their own rain".
- ^ Kimbrough, Liz (16 September 2022). "More droughts are coming, and the Amazon can't keep up: Study". Mongabay.
- ^ Derouin, Sarah (6 January 2022). "Deforestation: facts, causes & effects". Live Science.
- ^ "Deforestation". National Geographic.
- ^ "Eastern Deciduous Forest (U.S. National Park Service)". nps.gov.
- ^ Vogt, Kristina A, ed. (2007). "Global Societies and Forest Legacies Creating Today's Forest Landscapes". Forests and Society: Sustainability and Life Cycles of Forests in Human Landscapes. CABI. pp. 30–59. ISBN 978-1-84593-098-1.
- ^ "Deforestation and Its Effect on the Planet". National Geographic Environment. 7 February 2019. Archived from the original on 19 February 2021. Retrieved 21 July 2021.