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An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a
forest A forest is an area of land dominated by trees. 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' ...
that has attained great age without significant disturbance, and thereby exhibits unique ecological features, and might be classified as a
climax community In scientific ecology, climax community or climatic climax community is a historic term for a community of plants, animals, and fungi which, through the process of ecological succession in the development of vegetation in an area over time, hav ...
. The
Food and Agriculture Organization The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and the ecological processes are not significantly disturbed. More than one-third (34 percent) of the world's forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
that increases the
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
of the forested
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 ...
. Virgin or first-growth forests are old-growth forests that have never been logged. The concept of diverse tree structure includes multi-layered canopies and
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an ...
gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris. The world has 1.11 billion ha of primary forest remaining. Combined, three countries (Brazil, Canada, and Russia) host more than half (61 percent) of the world's primary forest. The area of primary forest has decreased by 81 million ha since 1990, but the rate of loss more than halved in 2010–2020 compared with the previous decade. Old-growth forests are valuable for economic reasons and for the
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 ...
they provide. This can be a point of contention when some in the
logging industry Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidder, skidding, on-site processing, and loading of trees or trunk (botany), logs onto logging truck, trucks or flatcar#Skeleton car, ...
desire to harvest valuable timber from the forests, while environmentalists seek to preserve the forests in their pristine state for benefits such as maintenance of biodiversity,
water purification Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for hu ...
,
flood control Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...
, and
nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
. Moreover, old-growth forests are more efficient at
sequestering carbon Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
than newly planted forests and fast-growing
timber plantations A tree plantation, forest plantation, plantation forest, timber plantation or tree farm is a forest planted for high volume production of wood, usually by planting one type of tree as a monoculture forest. The term ''tree farm'' also is used to ...
, thus preserving the forests is important to
climate change mitigation Climate change mitigation is action to limit climate change by reducing Greenhouse gas emissions, emissions of greenhouse gases or Carbon sink, removing those gases from the atmosphere. The recent rise in global average temperature is mostly caus ...
.


Characteristics

Old-growth forests tend to have large trees and standing dead trees, multilayered canopies with gaps that result from the deaths of individual trees, and
coarse woody debris Coarse woody debris (CWD) or coarse woody habitat (CWH) refers to fallen dead trees and the remains of large branches on the ground in forests and in rivers or wetlands.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). C ...
on the forest floor. A forest regenerated after a severe disturbance, such as wildfire, insect infestation, or harvesting, is often called
second-growth A secondary forest (or second-growth forest) is a forest or woodland area which has re-grown after a timber harvest or clearing for agriculture, until a long enough period has passed so that the effects of the disturbance are no longer evident. ...
or 'regeneration' until enough time passes for the effects of the disturbance to be no longer evident. Depending on the forest, this may take from a century to several millennia.
Hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
forests of the eastern United States can develop old-growth characteristics in 150–500 years. In British Columbia, Canada, old growth is defined as 120 to 140 years of age in the interior of the province where fire is a frequent and natural occurrence. In British Columbia's coastal
rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
s, old growth is defined as trees more than 250 years, with some trees reaching more than 1,000 years of age. In Australia, eucalypt trees rarely exceed 350 years of age due to frequent fire disturbance. Forest types have very different development patterns, natural disturbances and appearances. A
Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...
stand may grow for centuries without disturbance while an old-growth
ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is the ...
forest requires frequent surface fires to reduce the shade-tolerant species and regenerate the canopy species. In the
boreal forest of Canada 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 ...
, catastrophic disturbances like wildfires minimize opportunities for major accumulations of dead and downed woody material and other structural legacies associated with old growth conditions. Typical characteristics of old-growth forest include presence of older trees, minimal signs of human disturbance, mixed-age stands, presence of
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an ...
openings due to tree falls,
pit-and-mound topography Pit and mounds are small, persistent microtopographical features that present themselves after a disturbance event occurs and uproots trees via windthrow. The uprooted tree falls, and a pit forms in the forest floor where the root mass and associate ...
, down wood in various stages of decay, standing snags (dead trees), multilayered canopies, intact
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
s, a healthy
fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
ecosystem, and presence of indicator species.


Biodiversity

Old-growth forests are often
biologically diverse Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...
, and home to many rare species,
threatened species Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensa ...
, and
endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...
of plants and animals, such as the
northern spotted owl The northern spotted owl (''Strix occidentalis caurina'') is one of three spotted owl subspecies. A western North American bird in the family Strigidae, genus '' Strix'', it is a medium-sized dark brown owl native to the Pacific Northwest. An ...
, marbled murrelet and
fisher Fisher is an archaic term for a fisherman, revived as gender-neutral. Fisher, Fishers or The Fisher may also refer to: Places Australia *Division of Fisher, an electoral district in the Australian House of Representatives, in Queensland *Elect ...
, making them
ecologically Ecology () is the study of the relationships between living organisms, including humans, and their biophysical environment, physical environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosy ...
significant. Levels of
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
may be higher or lower in old-growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables, and geographic variables. Logging in old-growth forests is a contentious issue in many parts of the world. Excessive logging reduces biodiversity, affecting not only the old-growth forest itself, but also indigenous species that rely upon old-growth forest habitat.


Mixed age

Some forests in the old-growth stage have a mix of tree ages, due to a distinct
regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...
pattern for this stage. New trees regenerate at different times from each other, because each of them has a different spatial location relative to the main canopy, hence each one receives a different amount of light. The mixed age of the forest is an important criterion in ensuring that the forest is a relatively stable ecosystem in the long term. A
climax Climax may refer to: Language arts * Climax (narrative), the point of highest tension in a narrative work * Climax (rhetoric), a figure of speech that lists items in order of importance Biology * Climax community, a biological community th ...
stand that is uniformly aged becomes
senescent Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence inv ...
and degrades within a relatively short time to result in a new cycle of forest succession. Thus, uniformly aged stands are less stable ecosystems. Boreal forests are more uniformly aged, as they are normally subject to frequent stand replacing wildfires.


Canopy openings

Forest canopy In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns an ...
gaps are essential in creating and maintaining mixed-age stands. Also, some
herbaceous plant Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...
s only become established in canopy openings, but persist beneath an understory. Openings are a result of tree death due to small impact disturbances such as wind, low-intensity fires, and tree diseases. Old-growth forests are unique, usually having multiple horizontal layers of vegetation representing a variety of tree
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, age classes, and sizes, as well as "pit and mound" soil shape with well-established fungal nets. Because old-growth forest is structurally diverse, it provides higher-diversity habitat than forests in other stages. Thus, sometimes higher biological diversity can be sustained in old-growth forests, or at least a biodiversity that is different from other forest stages.


Topography

The characteristic
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...
of much old-growth forest consists of pits and mounds. Mounds are caused by decaying fallen trees, and pits (
tree throw In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are u ...
s) by the roots pulled out of the ground when trees fall due to natural causes, including being pushed over by animals. Pits expose
humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...
-poor, mineral-rich soil and often collect moisture and fallen leaves, forming a thick organic layer that is able to nurture certain types of organisms. Mounds provide a place free of leaf inundation and saturation, where other types of organisms thrive.


Standing snags

Standing
snags In forest ecology, a snag refers to a standing, dead or dying tree, often missing a top or most of the smaller branches. In freshwater ecology it refers to trees, branches, and other pieces of naturally occurring wood found sunken in rivers and ...
provide food sources and habitat for many types of organisms. In particular, many species of dead-wood predators such as
woodpecker Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
s must have standing snags available for feeding. In North America, the
spotted owl The spotted owl (''Strix occidentalis'') is a species of true owl. It is a resident species of old-growth forests in western North America, where it nests in tree hollows, old bird of prey nests, or rock crevices. Nests can be between high a ...
is well known for needing standing snags for nesting habitat.


Decaying ground layer

Fallen timber, or
coarse woody debris Coarse woody debris (CWD) or coarse woody habitat (CWH) refers to fallen dead trees and the remains of large branches on the ground in forests and in rivers or wetlands.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). C ...
, contributes
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
-rich
organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
directly to the
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
, providing a substrate for
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
es, fungi, and
seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embry ...
s, and creating microhabitats by creating relief on the forest floor. In some ecosystems such as the
temperate rain forest Temperate rainforests are coniferous or 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 North American P ...
of the North American
Pacific coast Pacific coast may be used to reference any coastline that borders the Pacific Ocean. Geography Americas Countries on the western side of the Americas have a Pacific coast as their western or southwestern border, except for Panama, where the Pac ...
, fallen timber may become
nurse log A nurse log is a fallen tree which, as it decays, provides ecological facilitation to seedlings. Broader definitions include providing shade or support to other plants. Some of the advantages a nurse log offers to a seedling are: water, moss thickn ...
s, providing a substrate for seedling trees.


Soil

Intact soils harbor many life forms that rely on them. Intact soils generally have very well-defined horizons, or
soil profile A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...
s. Different organisms may need certain well-defined soil horizons to live, while many trees need well-structured soils free of disturbance to thrive. Some herbaceous plants in northern hardwood forests must have thick duff layers (which are part of the soil profile).
Fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
ecosystems are essential for efficient '' in-situ'' recycling of nutrients back into the entire ecosystem.


Definitions


Ecological definitions


Stand age definition

Stand age can also be used to categorize a forest as old-growth. For any given geographical area, the average time since disturbance until a forest reaches the old growth stage can be determined. This method is useful, because it allows quick and objective determination of forest stage. However, this definition does not provide an explanation about forest function. It just gives a useful number to measure. So, some forests may be excluded from being categorized as old-growth even if they have old-growth attributes just because they are too young. Also, older forests can lack some old-growth attributes and be categorized as old-growth just because they are so old. The idea of using age is also problematic, because human activities can influence the forest in varied ways. For example, after the logging of 30% of the trees, less time is needed for old-growth to come back than after removal of 80% of the trees. Although depending on the species logged, the forest that comes back after a 30% harvest may consist of proportionately fewer hardwood trees than a forest logged at 80% in which the light competition by less important tree species does not inhibit the regrowth of vital hardwoods.


Forest dynamics definition

From a
forest dynamics Forest dynamics describes the underlying physical and biological forces that shape and change a forest ecosystem. The continuous state of change in forests can be summarized with two basic elements: disturbance and succession. Disturbance Forest ...
perspective, old-growth forest is in a stage that follows understory reinitiation stage. A review of the stages helps to understand the concept: # Stand-replacing: Disturbance hits the forest and kills most of the living trees. # Stand-initiation: A population of new trees becomes established. # Stem-exclusion: Trees grow higher and enlarge their
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an ...
, thus competing for the light with neighbors; light competition mortality kills slow-growing trees and reduces forest density, which allows surviving trees to increase in size. Eventually, the canopies of neighboring trees touch each other and drastically lower the amount of light that reaches lower layers. Due to that, the
understory In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abov ...
dies and only very
shade-tolerant In ecology, shade tolerance is a plant's ability to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes imprecise, especially in labeling of plants for sale in commercial ...
species survive. # Understory reinitiation: Trees die from low-level mortality, such as windthrow and diseases. Individual canopy gaps start to appear and more light can reach the forest floor. Hence, shade-tolerant species can establish in the understory. # Old-growth: Main canopy trees become older and more of them die, creating even more gaps. Since the gaps appear at different times, the understory trees are at different growth stages. Furthermore, the amount of light that reaches each understory tree depends on its position relative to the gap. Thus, each understory tree grows at a different rate. The differences in establishment timing and in growth rate create a population of understory trees that is variable in size. Eventually, some understory trees grow to become as tall as the main canopy trees, thereby filling the gap. This perpetuation process is typical for the old-growth stage. This, however, does not mean that the forest will be old-growth forever. Generally, three futures for old-growth stage forest are possible: 1) The forest will be hit by a disturbance and most of the trees will die, 2) Unfavorable conditions for new trees to regenerate will occur. In this case, the old trees will die and smaller plants will create
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 3) The regenerating understory trees are different species from the main canopy trees. In this case, the forest will switch back to stem-exclusion stage, but with shade tolerant tree species. 4) The forest in an old-growth stage can be stable for centuries, but the length of this stage depends on the forest's tree composition and the climate of the area. For example, frequent natural fires do not allow
boreal forests Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces ...
to be as old as coastal forests of
western North America Western North America is the western edge of the North American continent that borders the Pacific Ocean. It consists of Alaska at the farthest north, down through the western Canadian province of British Columbia, the western U.S. states of W ...
. Of importance is that while the stand switches from one tree community to another, the stand will not necessarily go through old-growth stage between those stages. Some tree species have a relatively open canopy. That allows more shade-tolerant tree species to establish below even before the understory reinitiation stage. The shade-tolerant trees eventually outcompete the main canopy trees in stem-exclusion stage. Therefore, the dominant tree species will change, but the forest will still be in stem-exclusion stage until the shade tolerant species reach old-growth stage. Tree species succession may change tree species' composition once the old-growth stage has been achieved. For example, an old boreal forest may contain some large aspen trees, which may die and be replaced by smaller balsam fir or black spruce. Consequently, the forest will switch back to understory reinitiation stage. Using the stand dynamics definition, old-growth can be easily evaluated using structural attributes. However, in some forest ecosystems, this can lead to decisions regarding the preservation of unique stands or attributes that will disappear over the next few decades because of natural succession processes. Consequently, using stand dynamics to define old-growth forests is more accurate in forests where the species that constitute old-growth have long lifespans and succession is slow.


Social and cultural definitions

Common
cultural Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ...
definitions and common denominators regarding what comprises old-growth forest, and of the variables that define, constitute and embody old-growth forests include: * The forest habitat possesses relatively mature, old trees; * The tree species present have long continuity on the same site; * The forest itself is a
remnant natural area A remnant natural area, also known as remnant habitat, is an ecological community containing native flora and fauna that has not been significantly disturbed by destructive activities such as agriculture, logging, pollution, development, fire supp ...
that has not been subjected to significant disturbance by mankind, altering the appearance of the landscape and its ecosystems, has not been subjected to logging (or other types of development such as road networks or housing), and has inherently progressed per natural tendencies. Additionally, in mountainous, temperate landscapes (such as Western North America), and specifically in areas of high-quality soil and a moist, relatively mild climate, some old-growth trees have attained notable height and girth (DBH: diameter at breast height), accompanied by notable biodiversity in terms of the species supported. Therefore, for most people, the physical size of the trees is the most recognized hallmark of old-growth forests, even though the ecologically productive areas that support such large trees often comprise only a very small portion of the total area that has been mapped as old-growth forest. (In high-altitude, harsh climates, trees grow very slowly and thus remain at a small size. Such trees also qualify as old growth in terms of how they are mapped, but are rarely recognized by the general public as such.) The debate over old-growth definitions has been inextricably linked with a complex range of social perceptions about
wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonurbanized land not under extensive agricultural cultivation. The term has traditionally re ...
preservation, biodiversity, aesthetics, and spirituality, as well as economic or industrial values.


Economic definitions

In logging terms, old-growth stands are past the economic optimum for harvestingusually between 80–150 years, depending on the species. Old growth forests were often given harvesting priority because they had the most commercially valuable timber, they were considered to be at greater risk of deterioration through root rot or insect infestation, and they occupied land that could be used for more productive second-growth stands. In some regions, old growth is not the most commercially viable timberin British Columbia, Canada, harvesting in the coastal region is moving to younger second-growth stands.


Other definitions

A 2001 scientific symposium in Canada found that defining old growth in a scientifically meaningful, yet policy-relevant, manner presents some basic difficulties, especially if a simple, unambiguous, and rigorous scientific definition is sought. Symposium participants identified some attributes of late-successional, temperate-zone, old-growth forest types that could be considered in developing an index of "old-growthness" and for defining old-growth forests: Structural features: * Uneven or multi-aged stand structure, or several identifiable age cohorts * Average age of dominant species approaching half the maximum longevity for species (about 150+ years for most shade-tolerant trees) * Some old trees at close to their maximum longevity (ages of 300+ years) * Presence of standing dead and dying trees in various stages of decay * Fallen, coarse woody debris * Natural regeneration of dominant tree species within canopy gaps or on decaying logs Compositional features: * Long-lived, shade-tolerant tree species associations (e.g., sugar maple, American beech, yellow birch, red spruce, eastern hemlock, white pine) Process features: * Characterized by small-scale disturbances creating gaps in the forest canopy * A long natural rotation for catastrophic or stand-replacing disturbance (e.g., a period greater than the maximum longevity of the dominant tree species) * Minimal evidence of human disturbance * Final stages of stand development before a relatively steady state is reached


Importance

* Old-growth forests often contain rich communities of plants and animals within the habitat due to the long period of forest stability. These varied and sometimes rare species may depend on the unique environmental conditions created by these forests. * Old-growth forests serve as a reservoir for species, which cannot thrive or easily regenerate in younger forests, so they can be used as a baseline for research. * Plant species that are
native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...
to old-growth forests may someday prove to be invaluable towards curing various human ailments, as has been realized in numerous plants in
tropical rainforests 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 equa ...
. * Old-growth forests also store large amounts of
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
above and below the ground (either as humus, or in wet soils as
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...
). They collectively represent a very significant store of carbon. Destruction of these forests releases this carbon as
greenhouse gases A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxide (), methane ...
, and may increase the risk of global
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Although old-growth forests therefore serve as a global
carbon dioxide 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 ...
, they are not protected by international treaties, because it is generally thought that aging forests cease to accumulate carbon. However, in forests between 15 and 800 years of age, net ecosystem productivity (the net carbon balance of the forest including soils) is usually positive; old-growth forests accumulate carbon for centuries and contain large quantities of it.


Ecosystem services

Old-growth 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 ...
that may be far more important to society than their use as a source of raw materials. These services include making breathable air, making pure water, carbon storage, regeneration of nutrients, maintenance of soils, pest control by insectivorous bats and insects, micro- and macro-climate control, and the storage of a wide variety of genes.


Climatic impacts

The effects of old-growth forests in relation to
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
has been contested in various studies and journals. 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 caused by human activities. The World Meteorological Organization (WMO) a ...
said in its 2007 report: "In the long term, a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber, fibre, or energy from the forest, will generate the largest sustained mitigation benefit." Old-growth forests are often perceived to be in equilibrium or in a state of decay. However, evidence from analysis of carbon stored above ground and in the soil has shown old-growth forests are more productive at storing carbon than younger forests. Forest harvesting has little or no effect on the amount of carbon stored in the soil, but other research suggests older forests that have trees of many ages, multiple layers, and little disturbance have the highest capacities for carbon storage. As trees grow, they remove carbon from the atmosphere, and protecting these pools of carbon prevents emissions into the atmosphere. Proponents of harvesting the forest argue the carbon stored in wood is available for use as
biomass energy Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...
(displacing fossil fuel use), although using biomass as a fuel produces air pollution in the form of
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
,
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
s,
volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s, particulates, and other pollutants, in some cases at levels above those from traditional fuel sources such as coal or natural gas. Each forest has a different potential to store carbon. For example, this potential is particularly high in the
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
where forests are relatively productive, trees live a long time, decomposition is relatively slow, and fires are infrequent. The differences between forests must, therefore, be taken into consideration when determining how they should be managed to store carbon. Old-growth forests have the potential to impact climate change, but climate change is also impacting old-growth forests. As the
effects of global warming The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice (glaciers), sea lev ...
grow more substantial, the ability of old-growth forests to sequester carbon is affected. Climate change showed an impact on the mortality of some dominant trees species, as observed in the Korean pine. Climate change also showed an effect on the composition of species when forests were surveyed over a 10- and 20-year period, which may disrupt the overall productivity of the forest.


Logging in old-growth forests

According to 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 under the leadership of James Gustave Speth. WRI's activities are focused on seven areas: food, fore ...
, as of January 2009, only 21% of the original old-growth forests that once existed on earth are remaining. An estimated one-half of Western Europe's forests were cleared before the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
, and 90% of the old-growth forests that existed in the
contiguous United States The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...
in the 1600s have been cleared.David Allan
Global deforestation
, Global change program, University of Michigan, 1 April 2010. Retrieved 24 May 2013
The large trees in old-growth forests are economically valuable, and have been subjected to aggressive logging around the world. This has led to much controversy between logging companies and
environmental group The environmental movement (sometimes referred to as the ecology movement), also including conservation and green politics, is a diverse philosophical, social, and political movement for addressing environmental issues. Environmentalists a ...
s. From certain forestry perspectives, fully maintaining an old-growth forest is seen as extremely economically unproductive, as timber can only be collected from falling trees, and also potentially damaging to nearby managed groves by creating environments conducive to root rot. It may be more productive to cut the old growth down and replace the forest with a younger one. The island of
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
, just off the southeast coast of Australia, has the largest amount of temperate old-growth
rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
reserves in Australia with around 1,239,000 hectares in total. While the local Regional Forest Agreement (RFA) was originally designed to protect much of this natural wealth, many of the RFA old-growth forests protected in Tasmania consist of trees of little use to the timber industry. RFA old-growth and high conservation value forests that contain species highly desirable to the forestry industry have been poorly preserved. Only 22% of Tasmania's original tall-eucalypt forests managed by
Forestry Tasmania Sustainable Timber Tasmania (formerly Forestry Tasmania) is a government business enterprise wholly owned by the Government of Tasmania, Australia. It is responsible for the management of public production forest in Tasmania, which is about 80 ...
have been reserved. Ten thousand hectares of tall-eucalypt RFA old-growth forest have been lost since 1996, predominantly as a result of industrial logging operations. In 2006, about 61,000 hectares of tall-eucalypt RFA old-growth forests remained unprotected. Recent logging attempts in the
Upper Florentine Valley The Upper Florentine Valley is a valley in the south of Tasmania, Australia, is an area recognised for its landscape and old growth forests. It is situated along the Gordon River Road near Maydena in the southwest of the island, roughly three h ...
have sparked a series of protests and media attention over the arrests that have taken place in this area. Additionally,
Gunns Limited Gunns Limited was a major forestry enterprise located in Tasmania, Australia. It had operations in forest management, woodchipping, sawmilling and veneer production. The company was placed into liquidation in March 2013. History Founded in 1 ...
, the primary forestry contractor in Tasmania, has been under recent criticism by political and environmental groups over its practice of
woodchipping Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste. Woodchips may be used as a biomass solid fuel and are raw material ...
timber harvested from old-growth forests.


Management

The increased understanding of forest dynamics in the late 20th century has led the scientific community to identify a need to inventory, understand, manage, and
conserve Conserve may refer to: * Conserve (condiment), a preserve made from a mixture of fruits or vegetables * Conserve (NGO), an Indian environmental organization * Conserve (publisher), a Dutch publisher * Conserved sequence, a protein or nucleic aci ...
representative examples of old-growth forests with their associated characteristics and values. The literature around old growth and its management is inconclusive about the best way to capture the true essence of an old-growth stand. A better understanding of natural systems has resulted in new ideas about forest management, such as managed natural disturbances should be designed to achieve the landscape patterns and habitat conditions that are normally maintained in
nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
. This coarse filter approach to biodiversity conservation recognizes ecological processes and provides for a dynamic distribution of old growth across the landscape. And all seral stagesyoung, medium and, oldsupport forest biodiversity. Plants and animals rely on different forest ecosystem stages to meet their habitat needs. In Australia, the
Regional Forest Agreement The Regional Forest Agreements (RFA) are 20 year plans for the conservation and sustainable management of Australia's native forests, and are intended to provide certainty to commercial forestry operations while protecting environmental values. The ...
(RFA) attempted to prevent the
clearfelling 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 and seed tree harvests, it is used by foresters to create certain types of forest ...
of defined "old-growth forests". This led to struggles over what constitutes "old growth". For example, in Western Australia, the timber industry tried to limit the area of old growth in the
karri ''Eucalyptus diversicolor'', commonly known as karri, is a species of flowering plant in the family Myrtaceae and is Endemism, endemic to the Southwest Australia, south-west of Western Australia. It is a tall tree with smooth light grey to cre ...
forests of the Southern Forests Region; this led to the creation of the Western Australian Forests Alliance, the splitting of the Liberal Government of Western Australia and the election of the
Gallop The canter and gallop are variations on the fastest gait that can be performed by a horse or other equine. The canter is a controlled three-beat gait, while the gallop is a faster, four-beat variation of the same gait. It is a natural gait pos ...
Labor Government. Old-growth forests in this region have now been placed inside
national parks A national park is a natural park in use for conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual ...
. A small proportion of old-growth forest also exists in South-West Australia, and is protected by federal laws from logging, which has not occurred there for more than 20 years. In British Columbia, Canada, old-growth forests must be maintained in each of the province's
ecological unit Ecological units, comprise concepts such as population, community, and ecosystem as the basic units, which are at the basis of ecological theory and research, as well as a focus point of many conservation strategies. The concept of ecological units ...
s to meet biodiversity needs.


Locations of remaining tracts

In 2006,
Greenpeace Greenpeace is an independent global campaigning network, founded in Canada in 1971 by Irving Stowe and Dorothy Stowe, immigrant environmental activists from the United States. Greenpeace states its goal is to "ensure the ability of the Earth t ...
identified that the world's remaining intact forest landscapes are distributed among the continents as follows: * 35% in South America: The
Amazon rainforest The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
is mainly located in Brazil, which clears a larger area of forest annually than any other country in the world. * 28% in North America, which harvests 10,000 km2 of ancient forests every year. Many of the fragmented forests of southern Canada and the United States lack adequate animal travel corridors and functioning ecosystems for large mammals. Most of the remaining old-growth forests in the
contiguous United States The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...
and
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
are on
public land In all modern states, a portion of land is held by central or local governments. This is called public land, state land, or Crown land (Australia, and Canada). The system of tenure of public land, and the terminology used, varies between countrie ...
. * 19% in
northern Asia North Asia or Northern Asia, also referred to as Siberia, is the northern region of Asia, which is defined in geographical terms and is coextensive with the Asian part of Russia, and consists of three Russian regions east of the Ural Mountains: ...
, home to the largest boreal forest in the world * 8% in Africa, which has lost most of its intact forest landscapes in the last 30 years. The timber industry and local governments are responsible for destroying huge areas of intact forest landscapes and continue to be the single largest threat to these areas. * 7% in South
Asia Pacific Asia-Pacific (APAC) is the part of the world near the western Pacific Ocean. The Asia-Pacific region varies in area depending on context, but it generally includes East Asia, Russian Far East, South Asia, Southeast Asia, Australia and Pacific Isla ...
, where the Paradise Forests are being destroyed faster than any other forest on Earth. Much of the large, intact forest landscapes have already been cut down, 72% in
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
, and 60% in
Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
. * Less than 3% in Europe, where more than 150 km2 of intact forest landscapes are cleared every year and the last areas of the region's intact forest landscapes in
European Russia European Russia (russian: Европейская Россия, russian: европейская часть России, label=none) is the western and most populated part of Russia. It is geographically situated in Europe, as opposed to the cou ...
are shrinking rapidly. In the United Kingdom, they are known as
ancient woodland In the United Kingdom, an ancient woodland is a woodland that has existed continuously since 1600 or before in England, Wales and Northern Ireland (or 1750 in Scotland). Planting of woodland was uncommon before those dates, so a wood present in 16 ...
s.


See also


Sources


References


Further reading


Provincial Old Growth regulations of British Columbia, Canada


from U.S. Regional Ecosystem Office
Collection of Google map links of clear cuts in or around old growth

Managing for Biodiversity in Young Forests
– U.S. Geological Survey Biological Science Report (pdf)
The State of British Columbia’s Forests Third Edition

BC Journal of Ecosystems Old growth definitions and management: A literature review

Natural Resources Canada Old-growth boreal forests: unraveling the mysteries


External links


Our disappearing forests

Rainforest Action Network

Ancient Forest Exploration & Research

Natural Resources Canada 2003

Old Growth Forest Definitions for Ontario





Archangel Ancient Tree Archive , Old Growth Trees
{{DEFAULTSORT:Old-Growth Forest Forest conservation Forestry and the environment Sustainable forest management Types of formally designated forests