Rainforest

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For other uses, see Rainforest (disambiguation).

Washington state
Rainforest at Mount Palung National Park, Borneo
Canopy of Khao Sok tropical rainforest
Stream in rainforests at Masoala National Park in Madagascar
Primitive tropical rainforest in Palawan
Rainforests in Pacific Rim National Park Reserve

Rainforests are forests characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropical rainforests or temperate rainforests, but other types have been described.

Estimates vary from 40% to 75% of all

indigenous to the rainforests.[1] There may be many millions of species of plants, insects and microorganisms 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 medicines have been discovered there.[2]

Rainforests as well as endemic rainforest species are rapidly disappearing due to

habitat loss and pollution of the atmosphere.[3]

Definition

Rainforests are characterized by a closed and continuous tree canopy, high humidity, the presence of moisture-dependent vegetation, a moist layer of leaf litter, the presence of epiphytes and lianas and the absence of wildfire. The largest areas of rainforest are tropical or temperate rainforests, but other vegetation associations including subtropical rainforest, littoral rainforest, cloud forest, vine thicket and even dry rainforest have been described.[4][5][6][7][8]

Tropical rainforest

Worldwide tropical rainforest climate zones.
Main article: Tropical rainforest

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 18 °C (64 °F) during all months of the year.[9] Average annual rainfall is no less than 168 cm (66 in) and can exceed 1,000 cm (390 in) although it typically lies between 175 cm (69 in) and 200 cm (79 in).[10]

Many of the world's

atmosphere through photosynthesis.[12][13]

Temperate rainforest

General distribution of temperate rainforests
Temperate rainforest in Pacific Rim National Park Reserve in Canada
Main article: Temperate rainforest

Tropical forests cover a large part of the globe, but temperate rainforests only occur in a few regions around the world.

temperate regions. They occur in North America (in the Pacific Northwest in Alaska, British Columbia, 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 coast, as well as in Galicia and coastal areas of the eastern Black Sea, including Georgia and coastal Turkey), in East Asia (in southern China, Highlands of Taiwan, much of Japan and Korea, and on Sakhalin Island and the adjacent Russian Far East coast), in South America (southern Chile) and also in Australia and New Zealand.[16]

Dry rainforest

Dry rainforests have a more open canopy layer than other rainforests,[17] and are found in areas of lower rainfall (630–1,100 mm (25–43 in)). They generally have two layers of trees.[18]

Layers

Main article: Stratification (vegetation)

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, understory and forest floor layers.[19][20]

Emergent layer

The emergent layer contains a small number of very large

canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall.[21][22] They need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Eagles, butterflies, bats and certain monkeys
inhabit this layer.

Canopy layer

Main article: Canopy (biology)
The canopy at the Forest Research Institute Malaysia showing crown shyness

The canopy layer contains the majority of the largest trees, typically 30 metres (98 ft) to 45 metres (148 ft) tall. The densest areas of

dendronautics.[23]

Understory layer

Main article: Understory

The understory or understorey layer lies between the canopy and the forest floor. It is home to a number of

shrub layer, although the shrub layer may also be considered a separate layer.[citation needed
]

Forest floor

Main article: Forest floor
Blue Mountains, Australia

The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants 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 decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of 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 rainforests.[24] Rainforests support a very broad array of fauna, including mammals, reptiles, amphibians, birds and invertebrates. Mammals may include primates, felids and other families. Reptiles include snakes, turtles, chameleons and other families; while birds include such families as vangidae and Cuculidae. Dozens of families of invertebrates are found in rainforests. 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 refuges,[25] 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 than would otherwise be possible.[26][27]

Some species of fauna show a trend towards declining populations in rainforests, for example, reptiles that feed on amphibians and reptiles. This trend requires close monitoring.[28] The seasonality of rainforests affects the reproductive patterns of amphibians, and this in turn can directly affect the species of reptiles that feed on these groups,[29] particularly species with specialized feeding, since these are less likely to use alternative resources.[30]

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 laterization process gives the oxisols a bright red colour and sometimes produces mineral 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 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.[31]

Effect on global climate

A natural rainforest emits and absorbs vast quantities of

water vapour). No rainforest today can be considered to be undisturbed.[33] Human-induced deforestation plays a significant role in causing rainforests to release carbon dioxide,[34][35][36] as do other factors, whether human-induced or natural, which result in tree death, such as burning and drought.[37] 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.[38]

Human uses

Aerial view of the Amazon rainforest, taken from a plane.
Further information: Tropical rainforest § Human dimensions

Tropical rainforests provide

sustainably by non-native peoples but are being exploited or removed for agricultural purposes
.

Native people

On 18 January 2007,

West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups.[42]
The tribes are in danger because of the deforestation, especially in Brazil.

Central African rainforest is home of the

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.[43] 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".[44]

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

Further information:
Deforestation of the Amazon Rainforest
Satellite photograph of the haze above Borneo and Sumatra, 24 September 2015

Tropical and temperate rainforests have been subjected to heavy legal and illegal logging for their valuable hardwoods and agricultural clearance (slash-and-burn, clearcutting) throughout the 20th century and the area covered by rainforests around the world is shrinking.[45] 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)[46] due to the removal of habitat with destruction of the rainforests.

Another factor causing the loss of rainforest is expanding urban areas. Littoral rainforest growing along coastal areas of eastern Australia is now rare due to ribbon development to accommodate the demand for seachange lifestyles.[47]

Forests are being destroyed at a rapid pace.

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.[54][unreliable source?
]

Several countries,[55] notably Brazil, have declared their deforestation a national emergency.[56] Amazon deforestation jumped by 69% in 2008 compared to 2007's twelve months, according to official government data.[57]

However, a 30 January 2009

degraded forest.[58]

See also

References

  1. ^ "Rainforests.net – Variables and Math". Archived from the original on 5 December 2008. Retrieved 4 January 2009.
  2. ^ "Rainforests at Animal Center". Animalcorner.co.uk. 1 January 2004. Archived from the original on 8 July 2012. Retrieved 26 August 2012.
  3. ^ "Impact of Deforestation – Extinction". Rainforests.mongabay.com. Retrieved 26 August 2012.
  4. ^ "Rainforests". Wet Tropics Management Authority. Retrieved 9 July 2021.
  5. ^ "Rainforests". The State of Queensland. Retrieved 9 July 2021.
  6. ^ "Rainforests". New South Wales Government Office of Environment and heritage. Retrieved 9 July 2021.
  7. ^ "Dry Rainforest". Tasmanian Government Department of Primary Industries, Parks, Water and Environment. Retrieved 9 July 2021.
  8. ^ "Western Sydney Dry Rainforest" (PDF). New South Wales Government Department of Planning, Industry and Environment. Retrieved 9 July 2021.
  9. ^ Susan Woodward. Tropical broadleaf Evergreen Forest: The rainforest. Archived 25 February 2008 at the Wayback Machine Retrieved on 14 March 2008.
  10. ^ 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.
  11. ^ Hobgood (2008). Global Pattern of Surface Pressure and Wind. Archived 18 March 2009 at the Wayback Machine Ohio State University. Retrieved on 8 March 2009.
  12. ^ Broecker, Wallace S. (2006). "Breathing easy: Et tu, O2." Columbia University Columbia.edu
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  17. ^ Coleby-Williams, Jerry (2020). "Kumbartcho Dry Rainforest". Gardening Australia. ABC. Retrieved 6 May 2022.
  18. ^ "Identification of Rainforest: Field Guide" (PDF). Department of Environment and Conservation. NSW Government. 2004. Retrieved 6 May 2022.
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  22. ^ "Sabah". Eastern Native Tree Society. Retrieved 14 November 2007.
  23. ^ "dendronautics". Archived from the original on 14 June 2006.
  24. ^ "Rainforest Facts". Rain-tree.com. Retrieved 26 August 2012.
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  28. ^ Barquero-González, J.P., Stice, T.L., Gómez, G., & Monge-Nájera, J. (2020). Are tropical reptiles really declining? A six-year survey of snakes in a tropical coastal rainforest: role of prey and environment. Revista de Biología Tropical, 68(1), 336–343.
  29. ^ Oliveira, M.E., & Martins, M. (2001). When and where to find a pitviper: activity patterns and habitat use of the lancehead, Bothrops atrox, in central Amazonia, Brazil. Herpetological Natural History, 8(2), 101-110.
  30. ^ Terborgh, J., & Winter, B. (1980). Some causes of extinction. Conservation Biology, 2, 119-133.
  31. ^ Baird, Dr. Chris S. "What makes the soil in tropical rainforests so rich?". Science Questions with Surprising Answers. Retrieved 11 April 2019.
  32. ^ "Grida.no" (PDF). Retrieved 26 August 2012.
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  37. ^ "Drought may turn forests into carbon producers". The Age. Melbourne. 6 March 2004.
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  39. ^ Myers, N. (1985). The primary source. W. W. Norton & Company, New York, pp. 189–193.
  40. ^ "Final Paper: The Medicinal Value of the Rainforest May 15, 2003. Amanda Haidet May 2003". Jrscience.wcp.muohio.edu. Retrieved 26 August 2012.
  41. ^ "Brazil sees traces of more isolated Amazon tribes". Reuters.com. 17 January 2007. Retrieved 26 August 2012.
  42. ^ "BBC: First contact with isolated tribes?". SurvivalInternational.org. 25 January 2007. Archived from the original on 6 February 2008. Retrieved 13 May 2020.
  43. ThinkQuest
  44. ^ "Indigenous People of the Rainforest". Rainforest Information Centre Educational Supplement. Retrieved 11 April 2019.
  45. ^ Entire rainforests set to disappear in next decade, The Independent 5 July 2003
  46. ^ Stevens, William K. (3 March 1992). "Talks Seek to Prevent Huge Loss of Species". The New York Times.
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  52. ^ "Science: Satellite monitors Madagascar's shrinking rainforest, 19 May 1990, New Scientist". Newscientist.com. 19 May 1990. Retrieved 26 August 2012.
  53. ^ China is black hole of Asia's deforestation, AsiaNews.it, 24 March 2008
  54. ^ "Palm oil – deforestation for everyday products – Rainforest Rescue". www.rainforest-rescue.org.
  55. Usatoday.com
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  56. guardian.co.uk
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  57. ^ "Brazil admits Amazon deforestation on the rise". NBC News. The Associated Press. 30 August 2008.
  58. ^ Rosenthal, Elisabeth (30 January 2009). "New Jungles Prompt a Debate on Rain Forests". The New York Times.

Further reading

View of the temperate rain forest in Mount Revelstoke National Park, British Columbia, Canada
Wikimedia Commons has media related to Rainforest.
Look up rainforest in Wiktionary, the free dictionary.
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