HOME
TheInfoList



Rainforests are
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 Food and Agricult ...
s characterized by high and continuous
rainfall Rain is liquid water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydr ...
, with annual rainfall in the case of
tropical rainforest File:Koppen-Geiger Map Af present.svg, upright=1.8, Tropical rainforest climate zones (Af). Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average p ...
s between and definitions varying by region for temperate rainforests. The
monsoon trough The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific,Bin WangThe Asian Monsoon.Retrieved 2008-05-03. as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such ...
, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continent A continent is one of several large landmasses. Generally identified by con ...
's tropical rainforests: which are distinct from monsoonal areas of
seasonal tropical forest A season is a division of the year based on changes in weather, ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and ...
. Estimates vary from 40% to 75% of all biotic
species In biology, a species is the basic unit of biological classification, 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 individu ...
are indigenous to the rainforests. There may be many millions of species of plants, insects and
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties ...
s still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the " world's largest pharmacy", because over one quarter of natural
medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their injury or dise ...
s have been discovered there. Rainforests are also responsible for 28% of the world's
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 ...
turnover, sometimes misnamed oxygen production, processing it through
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities. This chemical energy is stored ...

photosynthesis
from
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

carbon dioxide
and consuming it through respiration. Rainforests as well as endemic rainforest species are rapidly disappearing due to #Deforestation, deforestation, the resulting habitat loss and air pollution, pollution of the atmosphere.


Tropical

Tropical rainforests are characterized by a warm and wet climate with no substantial dry season: typically found within 10 degrees north and south of the equator. Mean monthly temperatures exceed during all months of the year. Average annual rainfall is no less than and can exceed although it typically lies between and .Newman, Arnold. The Tropical Rainforest : A World Survey of Our Most Valuable Endangered Habitat : With a Blueprint for Its Survival. New York: Checkmark, 2002. Print. Many of the world's tropical forests are associated with the location of the
monsoon trough The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific,Bin WangThe Asian Monsoon.Retrieved 2008-05-03. as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such ...
, also known as the intertropical convergence zone. The broader category of tropical moist forests are located in the Equator, equatorial zone between the Tropic of Cancer and Tropic of Capricorn. Tropical rainforests exist in Southeast Asia (from Burma, Myanmar (Burma)) to the Philippines, Malaysia, Indonesia, Papua New Guinea and Sri Lanka; also in Sub-Saharan Africa from the Cameroon to the Democratic Republic of the Congo, Congo (Congolian forests, Congo Rainforest), South America (e.g. the Amazon rainforest), Central America (e.g. Bosawás Biosphere Reserve, Bosawás, the southern Yucatán Peninsula-Petén Department, El Peten-Belize-Calakmul Biosphere Reserve, Calakmul), Australia, and on Pacific Islands (such as Hawaiian tropical rainforests, Hawaii). Tropical forests have been called the "Earth's lungs", although it is now known that rainforests contribute little net
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 ...
addition to the Earth's atmosphere, atmosphere through
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities. This chemical energy is stored ...

photosynthesis
.


Temperate

Tropical forests cover a large part of the globe, but temperate rainforests only occur in few regions around the world. Temperate rainforests are rainforests in temperateness, temperate regions. They occur in North America (in the Pacific Northwest in Alaska, British Columbia, Washington (state), Washington, Oregon and California), in Europe (parts of the British Isles such as the coastal areas of Ireland and Scotland, southern Norway, parts of the western Balkans along the Adriatic Sea, Adriatic coast, as well as in Galicia (Spain), Galicia and coastal areas of the eastern Black Sea, including Georgia (country), Georgia and coastal Turkey), in East Asia (in Northern and southern China, southern China, Highlands of Taiwan, much of Japan and Korea, and on Sakhalin, Sakhalin Island and the adjacent Temperate rainforests of the Russian Far East, Russian Far East coast), in South America (southern Chile) and also in Australia and New Zealand.


Layers

A tropical rainforest typically has a number of layers, each with different plants and animals adapted for life in that particular area. Examples include the emergent, canopy (biology), canopy, understory and forest floor layers.


Emergent layer

The emergent layer contains a small number of very large trees called emergents, which grow above the general Canopy (forest), canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. They need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Eagles, Butterfly, butterflies, bats and certain monkeys inhabit this layer.


Canopy layer

The canopy layer contains the majority of the largest trees, typically to tall. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops. The canopy, by some estimates, is home to 50 percent of all plant species. Epiphyte, Epiphytic plants attach to Trunk (botany), trunks and branches, and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer but more diverse. A quarter of all insect species are believed to exist in the rainforest canopy. Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, Natural history, naturalist William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles." A true exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Canopy research, Exploration of the canopy is still in its infancy, but other methods include the use of Balloon (aircraft), balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor. The science of accessing tropical forest canopy using airships or similar aerial platforms is called dendronautics.


Understory layer

The understory or understorey layer lies between the canopy and the forest floor. It is home to a number of birds, snakes and lizards, as well as predation, predators such as jaguars, boa (genus), boa constrictors and leopards. The leaves are much larger at this level and insect life is abundant. Many seedlings that will grow to the canopy level are present in the understory. Only about 5% of the sunlight shining on the rainforest canopy reaches the understory. This layer can be called a ''shrub layer'', although the shrub layer may also be considered a separate layer.


Forest floor

The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants Adaptation, adapted to low light can grow in this region. Away from riverbanks, swamps and clearings, where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. It also contains decomposition, decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of Fungus, fungi growing here help decay the animal and plant waste.


Flora and fauna

More than half of the world's species of plants and animals are found in the rainforest. Rainforests support a very broad array of fauna, including mammals, reptiles, amphibians, birds and invertebrates. Mammals may include primates, felidae, felids and other families. Reptiles include snakes, turtles, chameleons and other families; while birds include such families as vanga, vangidae and cuckoo, Cuculidae. Dozens of families of invertebrates are found in rainforests. Fungus, Fungi are also very common in rainforest areas as they can feed on the decomposing remains of plants and animals. The great diversity in rainforest species is in large part the result of diverse and numerous physical Refuge (ecology), refuges,, i.e. places in which plants are inaccessible to many herbivores, or in which animals can hide from predators. Having numerous refuges available also results in much higher total Biomass (ecology), biomass than would otherwise be possible.


Soils

Despite the growth of vegetation in a tropical rainforest, soil quality is often quite poor. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the Laterite, laterization process gives the oxisols a bright red colour and sometimes produces mineral deposition (geology), deposits such as bauxite. Most trees have roots near the surface because there are insufficient nutrients below the surface; most of the trees' minerals come from the top layer of decomposing leaves and animals. On younger substrates, especially of Volcano, volcanic origin, tropical soils may be quite fertile. If rainforest trees are cleared, rain can accumulate on the exposed soil surfaces, creating run-off, and beginning a process of soil erosion. Eventually, streams and rivers form and flooding becomes possible. There are several reasons for the poor soil quality. First is that the soil is highly acidic. The roots of plants rely on an acidity difference between the roots and the soil in order to absorb nutrients. When the soil is acidic, there is little difference, and therefore little absorption of nutrients from the soil. Second, the type of clay particles present in tropical rainforest soil has a poor ability to trap nutrients and stop them from washing away. Even if humans artificially add nutrients to the soil, the nutrients mostly wash away and are not absorbed by the plants. Finally, these soils are poor due to the high volume of rain in tropical rainforests washes nutrients out of the soil more quickly than in other climates.


Effect on global climate

A natural rainforest emits and absorbs vast quantities of
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

carbon dioxide
. On a global scale, long-term fluxes are approximately in balance, so that an undisturbed rainforest would have a small net impact on atmospheric carbon dioxide levels, though they may have other climatic effects (on cloud formation, for example, by recycling water vapour). No rainforest today can be considered to be undisturbed. Human-induced deforestation plays a significant role in causing rainforests to release carbon dioxide, as do other factors, whether human-induced or natural, which result in tree death, such as burning and drought. Some climate models operating with interactive vegetation predict a large loss of Amazonian rainforest around 2050 due to drought, forest dieback and the subsequent release of more carbon dioxide.


Human uses

Tropical rainforests provide timber as well as animal products such as meat and hides. Rainforests also have value as tourism destinations and for the ecosystem services provided. Many foods originally came from tropical forests, and are still mostly grown on plantations in regions that were formerly primary forest. Also, plant-derived medicines are commonly used for fever, fungal infections, burns, gastrointestinal problems, pain, respiratory problems, and wound treatment. At the same time, rainforests are usually not used sustainably by non-native peoples but are being Exploitation of natural resources, exploited or removed for agricultural expansion, agricultural purposes.


Native people

On January 18, 2007, Fundação Nacional do Índio, FUNAI reported also that it had confirmed the presence of 67 different uncontacted peoples, uncontacted tribes in Brazil, up from 40 in 2005. With this addition, Brazil has now overtaken the island of New Guinea as the country having the largest number of uncontacted tribes. The province of Irian Jaya or West Papua (Indonesian province), West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups. The tribes are in danger because of the deforestation, especially in Brazil. Central African rainforest is home of the Mbuti pygmies, one of the hunter-gatherer peoples living in equatorial rainforests characterised by their short height (below one and a half metres, or 59 inches, on average). They were the subject of a study by Colin Turnbull, ''The Forest People'', in 1962. Pygmies who live in Southeast Asia are, amongst others, referred to as “Negrito”. There are many tribes in the rainforests of the Malaysian state of Sarawak. Sarawak is part of Borneo, the third largest island in the world. Some of the other tribes in Sarawak are: the Kayan, Kenyah, Kejaman, Kelabit, Punan Bah, Tanjong, Sekapan, and the Lahanan. Collectively, they are referred to as Dayaks or Orangulu which means "people of the interior". About half of Sarawak's 1.5 million people are Dayaks. Most Dayaks, it is believed by anthropologists, came originally from the South-East Asian mainland. Their mythologies support this


Deforestation

Tropical rainforest, Tropical and temperate rainforests have been subjected to heavy logging, legal and illegal logging for their valuable Tropical timber, hardwoods and agricultural expansion, agricultural clearance (slash-and-burn, clearcutting) throughout the 20th century and the area covered by rainforests around the world is shrinking. Biologists have estimated that large numbers of species are being driven to extinction (possibly more than 50,000 a year; at that rate, says E. O. Wilson of Harvard University, a quarter or more of all species on Earth could be exterminated within 50 years) due to the removal of habitat with destruction of the rainforests. Another factor causing the loss of rainforest is expanding urban areas. Littoral zone, Littoral rainforest growing along coastal areas of eastern Australia is now rare due to ribbon development to accommodate the demand for seachange (demography), seachange lifestyles. Forests are being destroyed at a rapid pace. Almost 90% of West Africa's rainforest has been destroyed. Since the arrival of humans, Madagascar has lost two thirds of its original rainforest. At present rates, tropical rainforests in Indonesia would be logged out in 10 years and Papua New Guinea in 13 to 16 years. According to Rettet den Regenwald, Rainforest Rescue, an important reason for the increasing deforestation rate, especially in Indonesia, is the expansion of oil palm plantations to meet growing demand for cheap vegetable fats and biofuels. In Indonesia, palm oil is already cultivated on nine million hectares and, together with Malaysia, the island nation produces about 85 percent of the world's palm oil. Several countries, notably Brazil, have declared their deforestation a national emergency. Amazon deforestation jumped by 69% in 2008 compared to 2007's twelve months, according to official government data. However, a January 30, 2009 ''New York Times'' article stated, "By one estimate, for every acre of rainforest cut down each year, more than 50 acres of new forest are growing in the tropics." The new forest includes secondary forest on former farmland and so-called degraded forest.New Jungles Prompt a Debate on Rain Forests
The New York Times, January 30, 2009


See also

* Cloud forest * Ecology * Inland rainforest * Intact forest landscape * Jungle * Rainforest Foundation Fund * Sepilok Orang Utan Sanctuary * Stratification (vegetation) * Tapiche Ohara's Reserve


References


Further reading

. * Butler, R. A. (2005) ''A Place Out of Time: Tropical Rainforests and the Perils They Face''. Published online
Rainforests.mongabay.com
* Richards, P. W. (1996). ''The tropical rain forest''. 2nd ed. Cambridge University Press * Whitmore, T. C. (1998) ''An introduction to tropical rain forests''. 2nd ed. Oxford University Press.


External links


Animals in a rainforest

Rainforest Action Network

EIA forest reports
Investigations into illegal logging.
EIA in the USA
Reports and info.
The Coalition for Rainforest Nations

United Nations Forum on Forests


* [http://wikis.wheatonma.edu/rainforest Rainforest Plants]
Tropical rainforest for children



National Geographic: Rain forest


{{Authority control Rainforests, Biodiversity Forest ecology