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A forest is an area of land dominated by
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondar ...

tree
s. 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' 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." Using this definition, '' Global Forest Resources Assessment 2020'' (FRA 2020) found that forests covered , or approximately 31 percent of the world's land area in 2020. Forests are the predominant terrestrial
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

ecosystem
of Earth, and are found around the globe. More than half of the world's forests are found in only five countries (Brazil, Canada, China, Russia, and the United States). The largest share of forests (45 percent) are in the tropical latitudes, followed by those in the boreal, temperate, and subtropic domains. Forests account for 75% of the gross primary production of the Earth's biosphere, and contain 80% of the Earth's plant
biomass
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 forest Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic languages, Mongolic and Turkic languages, Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by pinophyta, conifero ...
s. Forests at different latitudes and elevations, and with different precipitation and
evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of water to the air directly from soil, Canopy interception, ...
form distinctly different
biome A biome () is a biogeographical unit consisting of a biological community (ecology), community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. ...
s: boreal forests around the North Pole, tropical moist forests and tropical dry forests around the
Equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the ...
, and temperate forests at the
middle latitudes The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer (latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Caprico ...
. Areas at higher elevations tend to support forests similar to those at higher latitudes, and the amount of precipitation also affects forest composition. Almost half the 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 . The remaining 20 percent is located in more than 34 million patches around the world – the vast majority less than in size. Human society and forests influence each other in both positive and negative ways. Forests provide
ecosystem services Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. Th ...
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.


Definition

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. 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, or was legally designated as a forest regardless of vegetation type. There are three broad categories of definitions of forest in use: administrative,
land use Land use involves the management and modification of natural environment or wilderness into built environment such as Human settlement, settlements and semi-natural habitats such as Arable land, arable fields, pastures, and managed Woodland, woo ...
, and land cover. Administrative definitions are based primarily upon the legal designations of land, and commonly bear little relationship to its vegetation: land that is legally designated as a forest is defined as such even if no trees are growing on it. 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, cleared roads or infrastructure within an area used for forestry—or areas that have been cleared by harvesting, disease, or fire—are still considered 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 In biology, the canopy is the aboveground portion of a plant community, plant cropping or crop, formed by the collection of individual Crown (botany), plant crowns. In forest ecology, canopy also refers to the upper layer or habitat zone, ...
(canopy cover) or the section of land that is occupied by the cross-section of tree trunks (basal area). Under such land-cover definitions, an area of land can only be known as forest if it is growing trees. Areas that fail to meet the land-cover definition may be still included while immature trees are present that are expected to meet the definition at maturity. Under land-use definitions, there is considerable variation on where the cutoff points are between a forest,
woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
, and
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the Canopy (forest), canopy does not close. The open canopy allows sufficient light to rea ...
. Under some definitions, to be considered a forest requires very high levels of tree canopy cover, from 60% to 100%, which excludes woodlands and savannas, which have a lower canopy cover. Other definitions consider savannas to be a type of forest, and include all areas with tree canopies over 10%. Some areas covered with trees are legally defined as agricultural areas, e.g.
Norway spruce ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern Europe, Northern, Central Europe, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, ...
plantations, under Austrian forest law, when the trees are being grown as Christmas trees and are below a certain height.


Etymology

The word ''
forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may ...
'' derives from the
Old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intel ...
''forest'' (also ''forès''), denoting "forest, vast expanse covered by trees"; ''forest'' was first introduced into English as the word denoting wild land set aside for hunting without necessarily having trees on the land. Possibly a borrowing, probably via
Frankish Frankish may refer to: * Franks, a Germanic tribe and their culture ** Frankish language or its modern descendants, Franconian languages * Francia, a post-Roman state in France and Germany * East Francia, the successor state to Francia in Germany ...
or
Old High German Old High German (OHG; german: Althochdeutsch (Ahd.)) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050. There is no standardised or supra-regional form of German at this period, and Old High ...
, of the
Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Church, Roman Catholic Western Europe during the Middle Ages. In this region it served as the primary written language, though local languages were also written to varying deg ...
, denoting "open wood",
Carolingian The Carolingian dynasty (; known variously as the Carlovingians, Carolingus, Carolings, Karolinger or Karlings) was a Franks, Frankish noble family named after Charlemagne, grandson of Mayor of the palace, mayor Charles Martel and a descendant ...
scribes first used ''foresta'' in the capitularies of
Charlemagne Charlemagne ( , ) or Charles the Great ( la, Carolus Magnus; german: Karl der Große; 2 April 747 – 28 January 814), a member of the Carolingian dynasty, was King of the Franks from 768, King of the Lombards from 774, and the first Holy ...
, specifically to denote the royal hunting grounds of the king. The word was not endemic to the Romance languages, e.g., native words for ''forest'' in the Romance languages derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
''silva'', which denoted "forest" and "wood(land)" ( cf. the English ''sylva'' and ''sylvan''; the Italian, Spanish, and Portuguese ''selva''; the Romanian ''silvă''; the Old French ''selve''). Cognates of forest in Romance languages—e.g., the Italian ''foresta'', Spanish and Portuguese ''floresta'', etc.—are all ultimately derivations of the French word. The precise origin of Medieval Latin is obscure. Some authorities claim the word derives from the
Late Latin Late Latin ( la, Latinitas serior) is the scholarly name for the form of Literary Latin of late antiquity.Roberts (1996), p. 537. English dictionary definitions of Late Latin date this period from the , and continuing into the 7th century in the ...
phrase ''forestam silvam'', denoting "the outer wood"; others claim the word is a latinisation of the Frankish *''forhist'', denoting "forest, wooded country", and was assimilated to ''forestam silvam'', pursuant to the common practice of Frankish scribes. The Old High German ''forst'' denoting "forest";
Middle Low German Middle Low German or Middle Saxon (autonym: ''Sassisch'', i.e. "Saxon", Standard German, Standard High German: ', Dutch language, Modern Dutch: ') is a developmental stage of Low German. It developed from the Old Saxon language in the Middle ...
''vorst'' denoting "forest";
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language English is a West Germanic languages, West Germanic language of the Indo-European language family, with its earliest forms spoken by the inhabita ...
''fyrhþ'' denoting "forest, woodland, game preserve, hunting ground" (English '' frith''); and
Old Norse Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and t ...
''fýri'', denoting "coniferous forest"; all of which derive from the
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the linguistic reconstruction, reconstructed proto-language of the Germanic languages, Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from ...
*''furhísa-'', *''furhíþija-'', denoting "a fir-wood, ''coniferous'' forest", from the
Proto-Indo-European Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo-E ...
*''perkwu-'', denoting "a ''coniferous'' or mountain forest, wooded height" all attest to the Frankish *''forhist''. Uses of ''forest'' in English to denote any uninhabited and unenclosed area are presently considered archaic. The Norman rulers of England introduced the word as a legal term, as seen in Latin texts such as the ''
Magna Carta (Medieval Latin for "Great Charter of Freedoms"), commonly called (also ''Magna Charta''; "Great Charter"), is a royal charter of rights agreed to by King John of England at Runnymede, near Windsor, Berkshire, Windsor, on 15 June 1215. ...
'', to denote uncultivated land that was legally designated for hunting by feudal
nobility Nobility is a social class found in many societies that have an aristocracy (class), aristocracy. It is normally ranked immediately below Royal family, royalty. Nobility has often been an Estates of the realm, estate of the realm with many e ...
(see
Royal Forest A royal forest, occasionally known as a kingswood (), is an area of land with different definitions in England, Wales, Scotland and Ireland. The term ''forest'' in the ordinary modern understanding refers to an area of wooded land; however, the ...
). These hunting forests did not necessarily contain any trees. Because that often included significant areas of woodland, "forest" eventually came to connote woodland in general, regardless of tree density. By the beginning of the fourteenth century, English texts used the word in all three of its senses: common, legal, and archaic. Other English words used to denote "an area with a high density of trees" are ''firth'', ''frith'', ''holt'', ''weald'', ''wold'', ''wood'', and ''woodland''. Unlike ''forest'', these are all derived from Old English and were not borrowed from another language. Some present classifications reserve ''woodland'' for denoting a locale with more open space between trees, and distinguish kinds of woodlands as ''open forests'' and ''closed forests'', premised on their crown covers. Finally, ''sylva'' (plural ''sylvae'' or, less classically, ''sylvas'') is a peculiar English spelling of the Latin ''silva'', denoting a "woodland", and has precedent in English, including its plural forms. While its use as a
synonym A synonym is a word, morpheme, or phrase In syntax and grammar, a phrase is a group of words or singular word acting as a grammatical unit. For instance, the English language, English expression "the very happy squirrel" is a noun phrase whi ...
of ''forest'', and as a
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
ate word denoting a woodland, may be admitted; in a specific technical sense it is restricted to denoting the ''species'' of trees that comprise the woodlands of a region, as in its sense in the subject of
silviculture Silviculture is the practice of controlling the growth, composition/structure, and quality of forests to meet values and needs, specifically lumber, timber production. The name comes from the Latin ('forest') and ('growing'). The study of forest ...
. The resorting to ''sylva'' in English indicates more precisely the denotation that the use of ''forest'' intends.


Evolutionary history

The first known forests on Earth arose in the
Late Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Dev ...
(approximately 380
million years ago The abbreviation Myr, "million years", is a unit of measurement, unit of a quantity of (i.e. ) years, or 31.556926 Terasecond and longer#Teraseconds, teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and co ...
), with the evolution of ''
Archaeopteris ''Archaeopteris'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the Endling, last individual of the ...
'', which was a plant that was both tree-like and fern-like, growing to in height. It quickly spread throughout the world, from the equator to subpolar latitudes; and it formed the first forest by being the first species known to cast shade due to its fronds and by forming soil from its roots. ''Archaeopteris'' was deciduous, dropping its fronds onto the forest floor, the shade, soil, and forest duff from the dropped fronds creating the first forest. The shed organic matter altered the freshwater environment, slowing its flow and providing food. This promoted freshwater fish.


Ecology

Forests account for 75% of the gross primary productivity of the Earth's biosphere, and contain 80% of the Earth's plant biomass. The world's forests contain about 606 gigatonnes of living biomass (above- and below-ground) and 59 gigatonnes of dead wood. The total biomass has decreased slightly since 1990, but biomass per unit area has increased. Forest ecosystems can be found in all regions capable of sustaining tree growth, at altitudes up to the
tree line The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snowp ...
, except where natural fire frequency or other disturbance is too high, or where the environment has been altered by human activity. The latitudes 10° north and south of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the ...
are mostly covered in
tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
, and the latitudes between 53°N and 67°N have
boreal forest Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic languages, Mongolic and Turkic languages, Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by pinophyta, conifero ...
. As a general rule, forests dominated by
angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
(''broadleaf forests'') are more species-rich than those dominated by
gymnosperms The gymnosperms ( Greek language, lit. revealed seeds) are a group of Spermatophyte, seed-producing plants that includes Pinophyta, conifers, cycads, ''Ginkgo'', and gnetophyta, gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm' ...
(''conifer'', ''montane'', or ''needleleaf forests''), although exceptions exist. Forests sometimes contain many tree species within a small area (as in
tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
s and
temperate deciduous forest Temperate deciduous or temperate broad-leaf forests are a variety of temperate forest 'dominated' by trees that lose their leaves each year. They are found in areas with warm moist summers and cool winters. The six major areas of this forest type ...
s), or relatively few species over large areas (e.g.,
taiga Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic languages, Mongolic and Turkic languages, Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by pinophyta, conifero ...
and arid
montane Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...
coniferous forests). Forests are often home to many animal and plant species, and
biomass Biomass is plant-based material used as a fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied ...
per unit area is high compared to other vegetation communities. Much of this biomass occurs below ground in the root systems and as partially decomposed plant
detritus In biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of Cell (biology), c ...
. The woody component of a forest contains
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...
, which is relatively slow to
decompose Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
compared with other organic materials such as
cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other ...
or carbohydrate. The biodiversity of forests varies considerably according to factors such as forest type, geography, climate, and soils – in addition to human use. Most forest habitats in temperate regions support relatively few animal and plant species, and species that tend to have large geographical distributions, while the montane forests of Africa, South America, Southeast Asia, and lowland forests of Australia, coastal Brazil, the Caribbean islands, Central America, and insular Southeast Asia have many species with small geographical distributions. Areas with dense human populations and intense agricultural land use, such as Europe, parts of Bangladesh, China, India, and North America, are less intact in terms of their biodiversity. Northern Africa, southern Australia, coastal Brazil, Madagascar, and South Africa are also identified as areas with striking losses in biodiversity intactness.


Components

A forest consists of many components that can be broadly divided into two categories: biotic (living) and abiotic (non-living). The living parts include
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondar ...

tree
s,
shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
s,
vine A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth Habit (biology), habit of trailing or wikt:scandent, scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to ...
s,
grass Poaceae () or Gramineae () is a large and nearly ubiquitous Family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species culti ...
es and other herbaceous (non-woody) plants,
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to ...
es,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
,
fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
,
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (ins ...
s,
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...
s,
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s,
reptile Reptiles, as most commonly defined are the animals in the Class (biology), class Reptilia ( ), a paraphyletic grouping comprising all sauropsid, sauropsids except birds. Living reptiles comprise turtles, crocodilians, Squamata, squamates (lizar ...
s,
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s, and microorganisms living on the plants and animals and in the soil, connected by
mycorrhizal network A Mycorrhizal network (also known as a common mycorrhizal network or CMN) is an underground network found in forests and other plant communities, created by the hypha A hypha (; ) is a long, branching, filamentous structure of a fungus ...
s.


Layers

A forest is made up of many layers. The main layers of all forest types are the forest floor, the understory, and the canopy. The emergent layer, above the canopy, exists in tropical rainforests. Each layer has a different set of plants and animals, depending upon the availability of sunlight, moisture, and food. * Forest floor contains decomposing leaves, animal droppings, and dead trees. Decay on the forest floor forms new soil and provides nutrients to the plants. The
forest floor The forest floor, also called detritus, wikt:duff#Noun 2, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shed vegetative parts, such as leaves, branches, bark, and stems, existing ...
supports ferns, grasses, mushroom, and tree seedlings. * Understory is made up of bushes, shrubs, and young trees that are adapted to living in the shade of the canopy. * Canopy is formed by the mass of intertwined branches, twigs, and leaves of mature trees. The crowns of the dominant trees receive most of the sunlight. This is the most productive part of the trees, where maximum food is produced. The canopy forms a shady, protective "umbrella" over the rest of the forest. * Emergent layer exists in a tropical rain forest and is composed of a few scattered trees that tower over the canopy. In botany and countries like Germany and Poland, a different classification of forest vegetation is often used: tree, shrub, herb, and moss layers (see
stratification (vegetation) Stratification in the field of ecology refers to the vertical layering of a habitat; the arrangement of vegetation in layers. It classifies the layers (sing. ''stratum'', pl. ''strata'') of vegetation largely according to the different heights to w ...
).


Types

Forests are classified differently and to different degrees of specificity. One such classification is in terms of the
biome A biome () is a biogeographical unit consisting of a biological community (ecology), community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. ...
s in which they exist, combined with leaf longevity of the dominant species (whether they are
evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, ...
or
deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, af ...
). Another distinction is whether the forests are composed predominantly of broadleaf trees,
conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...
ous (needle-leaved) trees, or mixed. *
Boreal forest Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic languages, Mongolic and Turkic languages, Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by pinophyta, conifero ...
s occupy the
subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of Hemiboreal, humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms ...
zone and are generally evergreen and coniferous. *
Temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
zones support both broadleaf deciduous forests (e.g.,
temperate deciduous forest Temperate deciduous or temperate broad-leaf forests are a variety of temperate forest 'dominated' by trees that lose their leaves each year. They are found in areas with warm moist summers and cool winters. The six major areas of this forest type ...
) and evergreen coniferous forests (e.g.,
temperate coniferous forests Temperate coniferous forest is a terrestrial ecoregion, terrestrial biome defined by the World Wide Fund for Nature. Temperate coniferous forests are found predominantly in areas with warm summers and cool winters, and vary in their kinds of plant ...
and
temperate rainforest Temperate rainforests are coniferous or Broad-leaved tree, broadleaf forests that occur in the temperate zone and receive heavy rain. Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of N ...
s). Warm temperate zones support broadleaf evergreen forests, including
laurel forest Laurel forest, also called laurisilva or laurissilva, is a type of Subtropics, subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glo ...
s. * Tropical and
subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
forests include tropical and subtropical moist forests, tropical and subtropical dry forests, and
tropical and subtropical coniferous forests Tropical and subtropical coniferous forests are a tropical forest habitat (ecology), habitat type defined by the World Wide Fund for Nature. These forests are found predominantly in North America, North and Central America and experience low level ...
. * Forests are classified according to physiognomy based on their overall physical structure or developmental stage (e.g.
old growth An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance (ecology), disturbance, and thereby exhibits un ...
vs. second growth). * Forests can also be classified more specifically based on the climate and the dominant tree species present, resulting in numerous different forest types (e.g.,
Ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large Pinus, pine tree species of variable habitat native plant, native to mountainous regions of western Nor ...
/
Douglas fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native plant, native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. Ther ...
forest). The number of trees in the world, according to a 2015 estimate, is 3 trillion, of which 1.4 trillion are in the tropics or sub-tropics, 0.6 trillion in the temperate zones, and 0.7 trillion in the coniferous boreal forests. The 2015 estimate is about eight times higher than previous estimates, and is based on tree densities measured on over 400,000 plots. It remains subject to a wide margin of error, not least because the samples are mainly from Europe and North America. Forests can also be classified according to the amount of human alteration.
Old-growth forest An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance (ecology), disturbance, and thereby exhibits un ...
contains mainly natural patterns of biodiversity in established seral patterns, and they contain mainly species native to the region and habitat. In contrast,
secondary forest A secondary forest (or second-growth forest) is a forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branch ...
is forest regrowing following timber harvest and may contain species originally from other regions or habitats. Different global forest classification systems have been proposed, but none has gained universal acceptance.
UNEP The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
- WCMC's forest category classification system is a simplification of other, more complex systems (e.g.
UNESCO The United Nations Educational, Scientific and Cultural Organization is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) aimed at promoting world peace and security through international coope ...
's forest and woodland 'subformations'). This system divides the world's forests into 26 major types, which reflect climatic zones as well as the principal types of trees. These 26 major types can be reclassified into 6 broader categories: temperate needleleaf, temperate broadleaf and mixed, tropical moist, tropical dry, sparse trees and parkland, and forest plantations. Each category is described in a separate section below.


Temperate needleleaf

Temperate needleleaf forests mostly occupy the higher latitudes of the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North ...
, as well as some warm temperate areas, especially on nutrient-poor or otherwise unfavourable
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organism In biology, an organism () is any life, living system that functions as an individual entity. All organi ...
s. These forests are composed entirely, or nearly so, of coniferous species (
Coniferophyta Conifers are a group of cone-bearing seed plants, a subset of gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gym ...
). In the Northern Hemisphere,
pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family (biology), family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanic ...
s ''Pinus'',
spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Earth. ''Picea'' is the sole gen ...
s ''Picea'',
larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains furth ...
es ''Larix'', firs ''Abies'', Douglas firs ''
Pseudotsuga ''Pseudotsuga'' is a genus of evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm cl ...
'', and hemlocks ''
Tsuga ''Tsuga'' (, from Japanese Japanese may refer to: * Something from or related to Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is b ...
'' make up the canopy; but other taxa are also important. In the Southern Hemisphere, most coniferous trees (members of
Araucariaceae Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods and the early Cenozoic, when it was distributed almost worldw ...
and
Podocarpaceae Podocarpaceae is a large Family (biology), family of mainly Southern Hemisphere conifers, known in English as podocarps, comprising about 156 species of evergreen trees and shrubs.James E. Eckenwalder. 2009. ''Conifers of the World''. Portland, O ...
) occur mixed with broadleaf species, and are classed as broadleaf-and-mixed forests.


Temperate broadleaf and mixed

Temperate broadleaf and mixed forest Temperate broadleaf and mixed forest is a temperate climate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth ...
s include a substantial component of trees of the
Anthophyta The anthophytes are a grouping of plant taxa bearing flower-like reproductive structures. They were formerly thought to be a clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, m ...
group. They are generally characteristic of the warmer temperate latitudes, but extend to cool temperate ones, particularly in the southern hemisphere. They include such forest types as the mixed deciduous forests of the United States and their counterparts in China and Japan; the broadleaf evergreen
rainforest Rainforests are characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or tem ...
s of Japan,
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
, and
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
; the
sclerophyllous Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaf, leaves, short Internode (botany), internodes (the distance between leaves along the stem) and leaf orientation which is paral ...
forests of Australia, central Chile, the
Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
, and California; and the southern beech
Nothofagus ''Nothofagus'', also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere in southern South America (Chile, Argentina) and Australasia (east and southeast Australia, New Zealand, New Gui ...
forests of Chile and New Zealand.


Tropical moist

There are many different types of tropical moist forests, with lowland evergreen broad-leaf
tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
s: for example várzea and igapó forests and the terra firme forests of the
Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countrie ...
; the
peat swamp forest Peat swamp forests are tropical and subtropical moist broadleaf forests, tropical moist forests where waterlogged soil prevents dead leaves and wood from fully decomposing. Over time, this creates a thick layer of acidic peat. Large areas of th ...
s;
dipterocarp Dipterocarpaceae is a family (biology), family of 16 genera and about 695 known species of mainly tropical lowland rainforest trees. The family name, from the type genus ''Dipterocarpus'', is derived from Greek language, Greek (''di'' = two, ''pt ...
forests of
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
; and the high forests of the
Congo Basin The Congo Basin (french: Bassin du Congo) is the sedimentary basin of the Congo River. The Congo Basin is located in Central Africa, in a region known as west equatorial Africa. The Congo Basin region is sometimes known simply as the Congo. It con ...
.
Seasonal tropical forest Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forests, typically contain a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropic ...
s, perhaps the best description for the colloquial term "
jungle A jungle is land covered with dense tropical forest, forest and tangled vegetation, usually in tropical climates. Application of the term has varied greatly during the past recent century. Etymology The word ''jungle'' originates from the Sans ...
", typically range from the rainforest zone 10 degrees north or south of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the ...
, to the
Tropic of Cancer The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be subsolar point, directly overhead. This occurs on the June solstice, when the Northern Hemisphere i ...
and
Tropic of Capricorn The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reach ...
. Forests located on mountains are also included in this category, divided largely into upper and lower
montane Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...
formations, on the basis of the variation of physiognomy corresponding to changes in altitude.


Tropical dry

Tropical dry forests are characteristic of areas in the tropics affected by seasonal drought. The seasonality of rainfall is usually reflected in the deciduousness of the forest canopy, with most trees being leafless for several months of the year. Under some conditions, such as less fertile soils or less predictable drought regimes, the proportion of evergreen species increases and the forests are characterised as "
sclerophyllous Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaf, leaves, short Internode (botany), internodes (the distance between leaves along the stem) and leaf orientation which is paral ...
". Thorn forest, a dense forest of low stature with a high frequency of thorny or spiny species, is found where drought is prolonged, and especially where grazing animals are plentiful. On very poor soils, and especially where fire or herbivory are recurrent phenomena,
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the Canopy (forest), canopy does not close. The open canopy allows sufficient light to rea ...
s develop.


Sparse trees and savanna

Sparse trees and
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the Canopy (forest), canopy does not close. The open canopy allows sufficient light to rea ...
are forests with sparse tree- canopy cover. They occur principally in areas of transition from forested to non-forested landscapes. The two major zones in which these
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

ecosystem
s occur are in the
boreal Boreal may refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernander sequence of northern Europe, during the Holocene epoch *Boreal climate, a climate characterized by long winters and short, cool to mild ...
region and in the seasonally dry tropics. At high latitudes, north of the main zone of boreal forestland, growing conditions are not adequate to maintain a continuously closed
forest cover Forest cover is the amount of forest that covers a particular area of land. It may be measured as relative (in percent) or absolute (in square kilometres/square miles). Around a third of the world's surface is covered with forest, with closed-canop ...
, so tree cover is both sparse and discontinuous. This vegetation is variously called open
taiga Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic languages, Mongolic and Turkic languages, Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by pinophyta, conifero ...
, open
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among hypha, filaments of multiple fungus, fungi species in a mutualism (biology), mutualistic relationship.woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other Herbaceous plant, herbs. Grassl ...
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

ecosystem
characterized by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken
herbaceous Herbaceous plants are vascular plants that have no persistent wood, woody stems above ground. This broad category of plants includes many perennial plant, perennials, and nearly all Annual plant, annuals and Biennial plant, biennials. Definition ...
layer that consists primarily of grasses. Savannas maintain an open canopy despite a high tree density.


Plantations

Forest plantations are generally intended for the production of timber and
pulpwood Pulpwood is timber with the principal use of making wood pulp for paper production. Applications * Trees raised specifically for pulp production account for 15% of world pulp production, old growth forests 9% and second- and third- and more gener ...
. Commonly mono-specific, planted with even spacing between the trees, and intensively managed, these forests are generally important as habitat for native
biodiversity Biodiversity or biological diversity is the variety and variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem d ...
. Some are managed in ways that enhance their biodiversity protection functions and can provide ecosystem services such as nutrient capital maintenance, watershed and soil structure protection and carbon storage.


Area

The annual net loss of forest area has decreased since 1990, but the world is not on track to meet the target of the United Nations Strategic Plan for Forests to increase forest area by 3 percent by 2030. While
deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then land conversion, converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban area, urban ...
is taking place in some areas, new forests are being established through natural expansion or deliberate efforts in other areas. As a result, the net loss of forest area is less than the rate of deforestation; and it, too, is decreasing: from per year in the 1990s to per year during 2010–2020. In absolute terms, the global forest area decreased by between 1990 and 2020, which is an area about the size of Libya.


Societal significance

Forests provide a diversity of
ecosystem services Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. Th ...
including: * Converting
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetraval ...
into
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...
and biomass. A full-grown tree produces about of net oxygen per year. * Acting as a
carbon sink A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere. Globally, the two most important carbon si ...
. Therefore, they are necessary to mitigate climate change. According to the Special Report on Global Warming of 1.5 °C of the
Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to advance scientific knowledge about climate change Attribution of recent climate change, caused by human activities. The Worl ...
, to avoid temperature rise by more than 1.5 degrees above pre-industrial levels, there will need to be an increase in global forest cover equal to the land area of Canada () by 2050. * Aiding in regulating
climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
. For example, research from 2017 shows that forests induce rainfall. If the forest is cut, it can lead to
drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D.  Jiang, A.  Khan, W.  Pokam Mba, D.  Rosenfeld, J. Tierney, an ...
, and in the tropics to occupational heat stress of outdoor workers. * Purifying
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
. * Mitigating natural hazards such as
flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study o ...
s. * Serving as a genetic reserve. * Serving as a source of
lumber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...
and as
recreation Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for happiness, enjoyment, amusement, ...
al areas. * Serving as a source of woodlands and trees for millions of people dependent almost entirely on forests for subsistence for their essential fuelwood, food, and fodder needs. Some researchers state that forests do not only provide benefits, but can in certain cases also incur costs to humans. Forests may impose an economic burden, diminish the enjoyment of natural areas, reduce the food-producing capacity of grazing land and cultivated land, reduce biodiversity, reduce available water for humans and wildlife, harbour dangerous or destructive wildlife, and act as reservoirs of human and livestock disease.


Management

The management of forests is often referred to as
forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests, woodlands, and associated resources for human and environmental benefits. Forestry is practiced in plantations and natural Stand level ...
. Forest management has changed considerably over the last few centuries, with rapid changes from the 1980s onward, culminating in a practice now referred to as
sustainable forest management Sustainable forest management (SFM) is the Forest management, management of forests according to the principles of sustainable development. Sustainable forest management has to keep the balance between three main pillars: Natural environment, eco ...
. Forest ecologists concentrate on forest patterns and processes, usually with the aim of elucidating cause-and-effect relationships.
Forester A forester is a person who practises forestry, the science, art, and profession of managing forests. Foresters engage in a broad range of activities including Restoration ecology, ecological restoration and management of Protected forest, protec ...
s who practice sustainable forest management focus on the integration of ecological, social, and economic values, often in consultation with local communities and other stakeholders. Humans have generally decreased the amount of forest worldwide. Anthropogenic factors that can affect forests include logging,
urban sprawl Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city." Urban sprawl has been described as the unrestricted growt ...
, human-caused
forest fire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
s,
acid rain Acid rain is rain or any other form of Precipitation (meteorology), precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists b ...
,
invasive species An invasive species otherwise known as an alien is an introduced species, introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, i ...
, and the
slash and burn Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a Field (agriculture), field called a swidden. The method begins by cutting down the trees and woody plants in an ar ...
practices of swidden agriculture or
shifting cultivation Shifting cultivation is an agricultural Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Dome ...
. The loss and re-growth of forests lead to a distinction between two broad types of forest: primary or
old-growth forest An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance (ecology), disturbance, and thereby exhibits un ...
and
secondary forest A secondary forest (or second-growth forest) is a forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branch ...
. There are also many natural factors that can cause changes in forests over time, including
forest fires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
,
insects Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (ins ...
,
diseases A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medica ...
, weather, competition between species, etc. In 1997, the
World Resources Institute The World Resources Institute (WRI) is a global research non-profit organization established in 1982 with funding from the MacArthur Foundation The John D. and Catherine T. MacArthur Foundation is a private foundation that makes grants and ...
recorded that only 20% of the world's original forests remained in large intact tracts of undisturbed forest. More than 75% of these intact forests lie in three countries: the boreal forests of Russia and Canada, and the rainforest of Brazil. According to Food and Agriculture Organization's (FAO) ''Global Forest Resources Assessment 2020'', an estimated of forest have been lost worldwide through deforestation since 1990, but the rate of forest loss has declined substantially. In the most recent five-year period (2015–2020), the annual rate of deforestation was estimated at , down from annually in 2010–2015. China instituted a ban on logging, beginning in 1998, due to the erosion and flooding that it caused. In addition, ambitious tree-planting programmes in countries such as China, India, the United States, and Vietnam – combined with natural expansion of forests in some regions – have added more than of new forests annually. As a result, the net loss of forest area was reduced to per year between 2000 and 2010, down from annually in the 1990s. In 2015, a study for ''
Nature Climate Change ''Nature Climate Change'' is a monthly peer-reviewed scientific journal published by Nature Publishing Group covering all aspects of research on global warming, the current climate change, especially effects of global warming, its effects. It was e ...
'' showed that the trend has recently been reversed, leading to an "overall gain" in global biomass and forests. This gain is due especially to
reforestation Reforestation (occasionally, reafforestation) is the natural or intentional restocking of existing forests and woodlands (forestation) that have been depleted, usually through deforestation, but also after clearcutting. Management A debate ...
in China and Russia. New forests are not equivalent to old growth forests in terms of species diversity, resilience, and carbon capture. On 7 September 2015, the FAO released a new study stating that over the last 25 years the global
deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then land conversion, converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban area, urban ...
rate has decreased by 50% due to improved management of forests and greater government protection. There is an estimated of forest in protected areas worldwide. Of the six major world regions, South America has the highest share of forests in protected areas, at 31 percent. The area of such areas globally has increased by since 1990, but the rate of annual increase slowed in 2010–2020. Smaller areas of
woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
in cities may be managed as
urban forestry Urban forestry is the care and management of single trees and tree populations in Urban area, urban settings for the purpose of improving the urban environment. Urban forestry involves both planning and management, including the programming o ...
, sometimes within public parks. These are often created for human benefits; Attention Restoration Theory argues that spending time in nature reduces stress and improves health, while forest schools and
kindergartens Kindergarten is a preschool educational approach based on playing, singing, practical activities such as drawing, and social interaction as part of the transition from home to school. Such institutions were originally made in the late 18th cent ...
help young people to develop social as well as scientific skills in forests. These typically need to be close to where the children live.


Canada

Canada has about of forest land. More than 90% of forest land is publicly owned and about 50% of the total forest area is allocated for harvesting. These allocated areas are managed using the principles of sustainable forest management, which include extensive consultation with local stakeholders. About eight percent of Canada's forest is legally protected from resource development. Much more forest land—about 40 percent of the total forest land base—is subject to varying degrees of protection through processes such as integrated
land use planning Land use planning is the process of regulating the Land use, use of land by a central authority. Usually, this is done to promote more desirable social and environmental outcomes as well as a more efficient use of resources. More specifically, ...
or defined management areas, such as certified forests. By December 2006, over of forest land in Canada (about half the global total) had been certified as being sustainably managed.
Clearcutting Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with Shelterwood cutting, shelterwood and Seed tree, seed tree harvests, it is used by foresters to ...
, first used in the latter half of the 20th century, is less expensive, but devastating to the environment; and companies are required by law to ensure that harvested areas are adequately regenerated. Most Canadian provinces have regulations limiting the size of new clear-cuts, although some older ones grew to over several years. The Canadian Forest Service is the government department which looks after Forests in Canada.


Latvia

Latvia has about of forest land, which equates to about 50.5% of Latvia's total area of of forest land (46% of total forest land) is publicly owned and of forest land (54% of the total) is in private hands. Latvia's forests have been steadily increasing over the years, which is in contrast to many other nations, mostly due to the forestation of land not used for agriculture. In 1935, there were only of forest; today this has increased by more than 150%. Birch is the most common tree at 28.2%, followed by pine (26.9%), spruce (18.3%), grey alder (9.7%), aspen (8.0%), black alder (5.7%), oak/ash (1.2%), with other hardwood trees making up the rest (2.0%).


United States

In the United States, most forests have historically been affected by humans to some degree, though in recent years improved forestry practices have helped regulate or moderate large-scale impacts. The
United States Forest Service The United States Forest Service (USFS) is an agency of the United States Department of Agriculture, U.S. Department of Agriculture that administers the nation's 154 United States National Forest, national forests and 20 United States Nationa ...
estimated a net loss of about between 1997 and 2020; this estimate includes conversion of forest land to other uses, including urban and suburban development, as well as afforestation and natural reversion of abandoned crop and pasture land to forest. In many areas of the United States, the area of forest is stable or increasing, particularly in many northern states. The opposite problem from flooding has plagued national forests, with loggers complaining that a lack of thinning and proper forest management has resulted in large forest fires.


World size records


See also


Sources


References


External links


Forests in danger

Intact Forests
with maps and reports

by the Food and Agriculture Organization
CoolForests.org – Conservation Cools the Planet

Forest area is land under natural or planted stands of trees of at least 5 meters ''in situ'', whether productive or not, and excludes tree stands in agricultural production systems

Forest area (sq. km)
data from the
World Bank The World Bank is an international financial institution that provides loans and Grant (money), grants to the governments of Least developed countries, low- and Developing country, middle-income countries for the purpose of pursuing capital pro ...
's
World Development Indicators World Development Indicators (WDI) is the World Bank The World Bank is an international financial institution that provides loans and Grant (money), grants to the governments of Least developed countries, low- and Developing country, middle-inc ...
, made available by Google * * * {{Authority control Habitats Trees Ecosystems