Facts on Forests and Forestry

1. What is a forest?

1.1. What are the definitions of a forest?

There are different definitions of what constitutes a forest. The most significant differences concern:
• the legal classifications of land uses in a country (forest / agriculture / urban)
• the kind of vegetation that constitutes a forest.

1.1.1. Legal classifications

Some legal definitions of ‘forest’ are based on the actual vegetation on the ground, whereas other definitions are based on a defined land area which may have no vegetation on it at all but is legally under the jurisdiction of the national agency which manages forests and natural resources. India’s Forest Conservation Act of 1980 states that any land recorded as forest in any land record is legally forest land whether or not there is any vegetation on the land. The Philippines has a definition based on the slope of the land - any untitled land having a slope greater than 18% is considered to be forestland.

1.1.2. Classifications based on the kind of vegetation

"Not all countries classify shrubs or bamboos as trees, for example, and some countries count trees planted along roadsides or fruit trees and orchards as forest.
Each member country of the EU has its own specific definition of forests (and in Belgium, each of the three regions has its own definition of a forest). For inventory purposes, the European Commission has defined forestland as having at least 20% canopy closure (10% in Mediterranean forests) and a minimum area of 0.5 ha (1 ha = 0.01 km²)."

Consolidated TEXT produced by the CONSLEG system of the Office for Official Publications of the European Communities

There are also different definitions of what kind of plants count as ‘trees’. Bamboos are considered to be a grass in some countries, but in most Asian countries, bamboos are considered to be trees. In arid and semi-arid regions, shrubs and bushes may be the most common woody vegetation, but not all countries classify shrubs as trees. In China, the Ministry of Forestry includes windbreaks and some fruit orchards in its statistics while Korea specifically excludes orchards from its definition of forests.
In the 1990 FAO report, forests in developed countries were defined as areas of land with 20% tree cover. In the 2000 report, this definition was changed in order to harmonize it with the definition for developing countries which is 10% tree cover. In the case of Australia, this resulted, for example, in a net increase in the recorded forest cover from 40,000 km² (1990) to 158,000 km² (2000)
http://www.fao.org/forestry/fo/fra/main/index.jsp

For an exhaustive listing and analysis of definitions of forest around the world, see "Definitions of Forest, Deforestation, Afforestation, and Reforestation" by H. Gyde Lund, 2000. Available for download at: http://home.att.net/~gklund/DEFpaper.html

1.2. What are the different types of forest?

Forests are often broadly classified by biomes, which are forest types corresponding to the climatic regions of the earth in which they occur. There are three major forest biomes: tropical, temperate, and boreal.

	Within these biomes, a forest type is a group of similar forest ecosystems that are distinguishable from other groups by their species composition, productivity and/or crown closure. UNEP and WCMC have identified the world's forests in the map on the left, where each forest type is associated with a color. Click here to see the full image.

1.2.1. What are tropical forests?

• Data on tropical forests
• Tropical forest types

Tropical forests occur near the equator and are the most ecologically rich of all forest types. They are also one of the most threatened forest types due to logging and clearance for agriculture (see the section on ‘Deforestation’).

Rainforests are forests with high rainfall and humidity. Although they are perhaps the tropical forest type about which there is the most publicity, tropical rainforests are only one of many different tropical forest types. Other tropical forest types include dry coastal forests, montane cloud forests, and semi-arid savannah woodlands.

"A major characteristic of tropical forests is their distinct seasonality: winter is absent, and only two seasons are present (rainy and dry). The length of daylight is 12 hours and varies little. As a consequence of the long growing season and hours of daylight all year long, tropical forests regenerate quickly. Despite the regenerative capacity of tropical rainforests, timber harvest in the tropics is rarely followed by regeneration. Conversion to agriculture is often permanent or results in soil erosion. Timber harvest contracts are usually short term and provide little or no incentive for timber companies to replant. So little reforestation has been done in the tropics that many people believe these forests cannot be restored. However, these forests can be restored and there are many successful examples in India, Indonesia, and the Caribbean."

From "A Student Guide To Tropical Forest Conservation," J.Louise Mastrantonio and John K. Francis: http://www.fs.fed.us/global/lzone/student/tropical.htm

• Data on tropical forests

Some data on tropical forests from the University of California, Berkeley, Museum of Paleontology web site (note that these data are characteristic of humid tropical forests–arid and semi arid tropical forests are less dense than humid tropical forests, even though they may also be very diverse in species composition):

•The Canopy in tropical forests is multi-layered and continuous, allowing little light penetration.
•The flora is highly diverse: one square kilometer may contain as many as 100 different tree species.
•Trees are 25-35 m tall, with buttressed trunks and shallow roots, mostly evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines (lianas), ferns, mosses, and palms are present in tropical forests.
•Fauna include numerous birds, bats, small mammals, and insects."

• Tropical forest types

Within the tropical forest biome, there are several forests types, which are determined by seasonal distribution of rainfall:

• Evergreen rainforest: no dry season.
• Seasonal rainforest: short dry period in a very wet tropical region (the forest exhibits definite seasonal changes as trees undergo developmental changes simultaneously, but the general character of vegetation remains the same as in evergreen rainforests).
• Semi-evergreen forest: longer dry season (the upper tree storey consists of deciduous trees, while the lower storey is still evergreen).
• Moist/dry deciduous forest (monsoon): the length of the dry season increases further as rainfall decreases (all trees are deciduous).

http://www.ucmp.berkeley.edu/glossary/gloss5/biome/forests.html#tropical

1.2.2. What are temperate forests? 

• Data on temperate forests
• Temperate forest types

Temperate forests occur in eastern North America, northeastern Asia, and western and central Europe. Well-defined seasons with a distinct winter characterize this forest biome. Only scattered remnants of original temperate forests remain.

Well-defined seasons with a distinct winter characterize this forest biome. Moderate climate and a growing season of 140-200 days during 4-6 frost-free months distinguish temperate forests. Because the growing season is shorter, temperate forests regenerate more slowly than tropical forests.

"The temperate deciduous forest is a biome that is always changing. It has four distinct seasons: winter, spring, summer, and fall. Winters are cold and summers are warm. Temperate deciduous forests get between 30 and 60 inches of precipitation a year. Precipitation in this biome happens year round. Because the soil is very fertile and hardwood trees are good for building, this biome has some of the world's largest population centers in it."
From "Temperate Deciduous Forests, Natureworks"

Although the total extent of forest in the northern temperate biome has not changed much in recent years, in many areas, second-growth forests and plantations have steadily replaced the species-rich old-growth forests.

See: "Losses of Biodiversity and their Causes," World Resources Institute

• Data on Temperate forests

Temperature varies from -30° C to 30° C.
Precipitation (75-150 cm) is distributed evenly throughout the year.
Soil is fertile, enriched with decaying litter.
Canopy is moderately dense and allows light to penetrate, resulting in well-developed and richly diversified understorey vegetation and stratification of animals.
Flora is characterized by 3-4 tree species per square kilometer. Tree species include characteristic broadleaved species which lose their foliage annually such as oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, willow, and spring-flowering herbs. At higher elevations, in areas with lower temperatures, and in poorer soils, temperate conifers such as pines and firs predominate.
Fauna is represented by squirrels, rabbits, skunks, birds, deer, mountain lion, bobcat, timber wolf, fox, and black bear.

• Temperate forest types

Within the temperate forest biome, there are several forest types, which are determined by seasonal distribution of rainfall

• Moist conifer and evergreen broad-leaved forests: wet winters and dry summers (rainfall is concentrated in the winter months and winters are relatively mild).
• Dry conifer forests: at higher elevation zones; low precipitation.
• Mediterranean forests: precipitation is concentrated in winter, less than 1000 mm per year.
• Temperate coniferous: mild winters, high annual precipitation (greater than 2000 mm).
• Temperate broad-leaved rainforests: mild, frost-free winters, high precipitation (more than 1500 mm) evenly distributed throughout the year.

For a list of links related to Temperate Forests see:
http://www.eco-portal.com/Forests/Forest_Types/Temperate_Forests/welcome.asp

1.2.3. What are boreal forests?

• Data on boreal forests

Boreal forests, or taiga, represent the largest terrestrial biome. Boreal (meaning northern) forests can be found in areas with shorter, warm summers and long winters; there are boreal forests in Europe, Asia, Siberia, and North America. Because of the cold climates, plant life in the boreal forest is sturdy, consisting mainly of evergreens and other resilient vegetation.

Boreal forests occur between latitudes of 50 and 60 degrees north. They are found in the broad belt of Eurasia and North America: two-thirds of the boreal forests are in Siberia with the rest in Scandinavia, Alaska, and Canada. Seasons are divided into short, moist, and moderately warm summers and long, cold, and dry winters. The length of the growing season in boreal forests is 130 days at most.

Because boreal forests are found in regions with short summers and long winters, these forests regenerate slowly. However, plant life in these cold areas is sturdy, consisting mainly of evergreens and other resilient vegetation. The forest canopy is so dense that little light reaches the forest floor, thus the vegetation on the forest floor is thin. The forests consist mostly of evergreen conifers with needle-like leaves, such as pine (Pinus), fir (Abies), and spruce (Picea). There are also deciduous genera such as birch (Betula) and poplar (Populus).

See also:

http://www.eco-portal.com/Forests/Forest_Types/Boreal_Forests/welcome.asp

• Data on boreal forests

Temperatures are very low.
Precipitation is primarily in the form of snow, 40 to > 100 cm annually.
Soil is thin, nutrient-poor, and acidic.
Canopy permits low light penetration, and as a result, understory is limited.
Flora consist mostly of cold-tolerant evergreen conifers with needle-like leaves, such as pine, fir, and spruce.
Fauna include woodpeckers, hawks, moose, bear, weasel, lynx, fox, wolf, deer, hares, chipmunks, shrews, and bats.

Data from:
http://www.ucmp.berkeley.edu/glossary/gloss5/biome/forests.html#boreal

For an extensive set of links related to boreal forests see:
http://forests.org/links/Forest_Types/Boreal_Forests/

1.3. What is meant by natural or ‘frontier’ forests?

"Another classification of forests makes a distinction between ‘natural’ forest and forest plantations. There is some controversy concerning the definitions of both "natural forest" and "forest plantation." The controversy reflects the differing interests of groups who have a stake in the future of forests. These ‘stakeholders’ include—but are not limited to—forest industry interests who see forests as a source of raw material to produce timber or pulp; conservation groups who seek to maintain the biodiversity and environmental values of natural forests; people and institutions seeking to mitigate global warming by using forests for carbon sequestration (storage); and the representatives of landless people in some countries who see forest land as potential agricultural land."

1.3.1 Natural forests

"There is very little untouched forest left in the world. Almost every corner of the planet is directly or indirectly influenced by human activity. Forests are either directly affected by human activities such as cutting, planting and drainage, or indirectly by manipulation of the grazing regime, air pollution and other factors. These human activities have affected the distribution of natural species and influence the evolution of the landscape.

Strictly speaking, the term ‘natural forest’ (or forest which has not been affected by any human activity) only applies to a very few, very small remnants of forested land. Nevertheless, the term is often used. The official definition of natural forest used in Denmark provides a good, broad explanation of the term. "Natural forest originates from the original forest cover, i.e. a forest reproduced naturally. Natural forest is thus a forest which has spontaneously generated itself on the location and which consists of naturally immigrant tree species. Natural forests can be more or less influenced by culture, e.g. by logging or regeneration techniques, but the forests must not have been subject to regeneration by sowing or planting".
http://www.geus.dk/departments/environ-hist-climate/

"FAO uses a different definition of natural forest. In the Temperate and Boreal Forest Resources Assessment (TBFRA 2000), UN-Economic Commission for Europe and FAO use "naturalness" to describe the degree of resemblance to the condition that would obtain in the complete absence of human intervention. Forests and other wooded land are characterized as natural (undisturbed by man), semi-natural (under some degree of management, or evincing past human intervention) or plantation (under active management)."
http://www.metsa.fi/eng/tat/jointweek/pdf/varjo_fao.pdf

1.3.2 Frontier forests

"In a 1997 study, the World Resources Institute (WRI) coined the term "frontier forests" to describe forested areas that are relatively undisturbed by human activity and are large enough to maintain their biodiversity, including viable populations of wide-ranging species. According to WRI frontier forests constitute about 40% of total forest area.
http://www.wri.org/wri/ffi/

It is interesting to note that contrary to popular belief, many areas that might appear to be undisturbed forest are not in fact ‘pristine’ or ‘frontier’ forest. Ecological, historical, and archaeological studies have shown, for example, that even the Amazon forest has been inhabited, utilized and disturbed in many ways by humans for millennia."

1.3.3. The 'pristine' Amazon forest

Although the Amazon forest is commonly believed to be one of the earth’s largest expanses of untouched, ‘virgin’ forest, there is a growing consensus among ecologists, historians, and archaeologists that there are few parts of the region which have never been subject to human influence. Indeed, there is strong evidence now that the region has a long history of settlement and that over time, these settlements have modified the forest ecosystems.

Researchers in the Amazon have found unusual concentrations of plants used by humans, suggesting quite high human population densities in the past. Estimates of the human population at the time of the European conquests around 1500 range from 1 to 6 million (sometimes higher). The region’s population has only recently returned to these levels with the notable difference that nowadays they mostly live in towns and cities rather than farming in the forest. This population used to raise crops in managed fallows. The amount of cleared area in 1500 was probably close to that prevailing in 1990. Forest fires were probably as common as at present, but on a smaller scale. Overall these populations have significantly altered plant and animal distribution and densities. The notion of an undisturbed wild Amazonian forest is an artifact.

From: Amazonia - Resiliency and Dynamism of the Land and its People
By Nigel J.H. Smith, Emanuel Adilson S. Serrão, Paulo T. Alvim, and Italo C. Falesi
© The United Nations University, 1995