Estimates vary from 40% to 75% of all bioticspecies
to the rainforests.
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.
Rainforests are also responsible for 28% of the world's oxygen
turnover, sometimes misnamed oxygen production,
processing it through photosynthesis
from carbon dioxide
and consuming it through respiration.
Worldwide tropical rainforest climate zones.
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.
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).
Many of the world's tropical forests
are associated with the location of the monsoon trough
, also known as the intertropical convergence zone
The broader category of tropical moist forests
are located in the equatorial zone
between the Tropic of Cancer
and Tropic of Capricorn
. Tropical rainforests exist in Southeast Asia
(from Myanmar (Burma)
) to the Philippines
, Papua New Guinea
and Sri Lanka
; also in Sub-Saharan Africa
from the Cameroon
to the Congo
), South America
(e.g. the Amazon rainforest
), Central America
, the southern Yucatán Peninsula
, and on Pacific Islands
(such as Hawaiʻi
). Tropical forests have been called the "Earth's lungs
", although it is now known that rainforests contribute little net oxygen
addition to the atmosphere
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 temperate
regions. They occur in North America
(in the Pacific Northwest
, British Columbia
), in Europe
(parts of the British Isles
such as the coastal areas of Ireland
, 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 on Sakhalin Island
and the adjacent Russian Far East
coast), in South America
) and also in Australia
and New Zealand
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
and forest floor
The emergent layer
contains a small number of very large trees
, which grow above the general 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
and certain monkeys
inhabit this layer.
layer contains the majority of the largest trees, typically 30 metres (98 ft) to 45 metres (148 ft) 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. Epiphytic plants
attach to trunks
, 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, naturalistWilliam 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
. Exploration of the canopy
is still in its infancy, but other methods include the use of balloons
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
layer lies between the canopy and the forest floor. It is home to a number of birds
, as well as predators
such as jaguars
, boa constrictors
. 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.
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
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 the rainforest.
Rainforests support a very broad array of fauna
, including mammals
. Mammals may include primates
and other families. Reptiles include snakes
and other families; while birds include such families as vangidae
. 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
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.
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
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.
Effect on global climate
A natural rainforest emits and absorbs vast quantities of 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.
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.
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 exploited
or removed for agricultural purposes
On January 18, 2007, FUNAI
reported also that it had confirmed the presence of 67 different 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
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 Mbutipygmies
, 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
, 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
- ^ The Tropical Rain Forest. Marietta College. Marietta, Ohio. Retrieved 14 August 2013,
- ^ "Rainforests.net – Variables and Math". Archived from the original on 2008-12-05. Retrieved 2009-01-04.
- ^ "Rainforests at Animal Center". Animalcorner.co.uk. 2004-01-01. Archived from the original on 2012-07-08. Retrieved 2012-08-26.
- ^ Killer Inhabitants of the Rainforests. "Killer Inhabitants of the Rainforests". Trendsupdates.com. Retrieved 2012-08-26.
- ^ "Impact of Deforestation – Extinction". Rainforests.mongabay.com. Retrieved 2012-08-26.
- ^ Susan Woodward. Tropical broadleaf Evergreen Forest: The rainforest. Archived 2008-02-25 at the Wayback Machine Retrieved on 2008-03-14.
- ^ 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.
- ^ Hobgood (2008). Global Pattern of Surface Pressure and Wind. Archived 2009-03-18 at the Wayback Machine Ohio State University. Retrieved on 2009-03-08.
- ^ Broeker, Wallace S. (2006). "Breathing easy: Et tu, O2." Columbia University Columbia.edu
- ^ Moran, Emilio F. (1993). "Deforestation and land use in the Brazilian Amazon". Human Ecology. 21: 1–21. doi:10.1007/BF00890069. S2CID 153481315.
- ^ "The Temperate Rainforest".
- ^ Denslow, J S (November 1987). "Tropical Rainforest Gaps and Tree Species Diversity". Annual Review of Ecology and Systematics. 18 (1): 431–451. doi:10.1146/annurev.es.18.110187.002243. ISSN 0066-4162.
- ^ Bourgeron, Patrick S. (1983). "Spatial Aspects of Vegetation Structure". In Frank B. Golley (ed.). Tropical Rain Forest Ecosystems. Structure and Function. Ecosystems of the World (14A ed.). Elsevier Scientific. pp. 29–47. ISBN 0-444-41986-1.
- ^ "Sabah". Eastern Native Tree Society. Retrieved 2007-11-14.
- ^ Dendronautics – Introduction Archived June 14, 2006, at the Wayback Machine
- ^ "Rainforest Facts". Rain-tree.com. Retrieved 2012-08-26.
- ^ Ritchie, Euan G.; Johnson, Christopher N. (2009). "Predator interactions, mesopredator release and biodiversity conservation". Ecology Letters. 12 (9): 982–998. doi:10.1111/j.1461-0248.2009.01347.x. ISSN 1461-023X. PMID 19614756. S2CID 11744558.,
- ^ Sih, Andrew (1987). "Prey refuges and predator-prey stability". Theoretical Population Biology. 31: 1–12. doi:10.1016/0040-5809(87)90019-0.
- ^ McNair, James N. (1986). "The effects of refuges on predator-prey interactions: A reconsideration". Theoretical Population Biology. 29 (1): 38–63. doi:10.1016/0040-5809(86)90004-3. PMID 3961711.
- ^ Baird, Dr. Chris S. "What makes the soil in tropical rainforests so rich?". Science Questions with Surprising Answers. Retrieved 11 April 2019.
- ^ "Grida.no" (PDF). Retrieved 2012-08-26.
- ^ Lewis, S.L.; Phillips, O.L.; Baker, T.R.; Lloyd, J.; et al. (2004). "Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots". Phil. Trans. R. Soc. Lond. 359 (1443): 421–436. doi:10.1098/rstb.2003.1431. PMC 1693337. PMID 15212094.
- ^ Malhi, Yadvinder; Grace, John (2000). "Tropical forests and atmospheric carbon dioxide". Trends in Ecology & Evolution. 15 (8): 332–337. doi:10.1016/S0169-5347(00)01906-6. ISSN 0169-5347. PMID 10884705.
- ^ Malhi, Yadvinder; Phillips, Oliver, eds. (2005). Tropical Forests and Global Atmospheric Change. Oxford, New York: Oxford University Press. doi:10.1093/acprof:oso/9780198567066.001.0001. ISBN 9780198567066. OCLC 77178196.
- ^ Baccini, A.; Walker, W.; Carvalho, L.; Farina, M.; Sulla-Menashe, D.; Houghton, R. A. (2017-10-13). "Tropical forests are a net carbon source based on aboveground measurements of gain and loss". Science. 358 (6360): 230–234. Bibcode:2017Sci...358..230B. doi:10.1126/science.aam5962. ISSN 0036-8075. PMID 28971966.
- ^ "Drought may turn forests into carbon producers". The Age. Melbourne. 2004-03-06.
- ^ Cox, P. M.; Betts, R. A.; Collins, M.; Harris, P. P.; Huntingford, C.; Jones, C. D. (2004). "Amazonian forest dieback under climate-carbon cycle projections for the 21st century" (PDF). Theoretical and Applied Climatology. 78 (1–3): 137. Bibcode:2004ThApC..78..137C. doi:10.1007/s00704-004-0049-4. S2CID 5122043. Archived from the original(PDF) on January 9, 2007.
- ^ Myers, N. (1985). The primary source. W. W. Norton & Company, New York, pp. 189–193.
- ^ "Final Paper: The Medicinal Value of the Rainforest May 15, 2003. Amanda Haidet May 2003". Jrscience.wcp.muohio.edu. Retrieved 2012-08-26.
- ^ "Brazil sees traces of more isolated Amazon tribes". Reuters.com. 2007-01-17. Retrieved 2012-08-26.
- ^ "BBC: First contact with isolated tribes?". SurvivalInternational.org. 2007-01-25. Archived from the original on 2008-02-06. Retrieved 2020-05-13.
- ^ The Tribal Peoples Archived 2012-10-20 at the Wayback Machine, ThinkQuest
- ^ "Indigenous People of the Rainforest". Rainforest Information Centre Educational Supplement. Retrieved 11 April 2019.
- ^ Entire rainforests set to disappear in next decade, The Independent 5 July 2003
- ^ Talks Seek to Prevent Huge Loss of Species, New York Times 3 March 1992
- ^ "Littoral Rainforest-Why is it threatened?". Pittwater.nsw.gov.au. 2012-08-09. Retrieved 2012-08-26.
- ^ Thomas Marent: Out of the woods, The Independent 28 September 2006
- ^ Brazil: Amazon Forest Destruction Rate Has Tripled, FoxNews.com, September 29, 2008
- ^ "Papua New Guinea's rainforests disappearing faster than thought". News.mongabay.com. Archived from the original on 2008-06-08. Retrieved 2012-08-26.
- ^ "Rainforests & Agriculture". Csupomona.edu. Archived from the original on 2012-09-30. Retrieved 2012-08-26.
- ^ "Science: Satellite monitors Madagascar's shrinking rainforest, 19 May 1990, New Scientist". Newscientist.com. 1990-05-19. Retrieved 2012-08-26.
- ^ China is black hole of Asia's deforestation, AsiaNews.it, 24 March 2008
- ^ Rainforest Rescue: Facts about palm oil
- ^ Amazon deforestation rises sharply in 2007, Usatoday.com, January 24, 2008
- ^ Vidal, John (20 May 2005). "Rainforest loss shocks Brazil". guardian.co.uk. London. Retrieved 7 July 2010.
- ^ Brazil: Amazon deforestation worsens, NBC News, August 30, 2008
- ^ New Jungles Prompt a Debate on Rain Forests, The New York Times, January 30, 2009
Wikimedia Commons has media related to Rainforest
Look up rainforest
in Wiktionary, the free dictionary.
Last edited on 7 March 2021, at 19:48
Content is available under CC BY-SA 3.0
unless otherwise noted.