Amazon Rainforest
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The Amazon Rainforest is a moist broadleaf forest in the Amazon Basin of South America. It encompasses 7 million km² (1.2 billion acres), with parts located within nine nations: Brazil (with 60% of the rainforest), Colombia, Peru, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana. This forest represents over half of the planet's remaining rainforests. States or departments in four nations bear the name Amazonas for the Amazon. Amazonian rainforests comprise the largest and most species rich tract of tropical rainforest that exists.
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Biodiversity
Image:Amazon 57.53278W 2.71207S.jpg Wet tropical forests are the most species-rich biome, and tropical forests in the Americas are consistently more species rich than the wet forests in Africa and Asia<ref name ="Turner 2001">Turner, I.M. 2001. The ecology of trees in the tropical rain forest. Cambridge University Press, Cambridge. ISBN 0521801834</ref>. As the largest tract of tropical rainforest in the Americas, the Amazonian rainforests have unparalleled biodiversity.
The region is home to ~2.5 million insect species, tens of thousands of plants, and some 2000 birds and mammals. To date, at least 40,000 plant species, 3,000 fishes, 1,294 birds, 427 mammals, 427 amphibians, and 378 reptiles have been scientifically classified in the region <ref name = "Da Silva 2005">Da Silva et al. 2005. The Fate of the Amazonian Areas of Endemism. Conservation Biology 19 (3), 689-694</ref>. Scientists have described between 96,660 and 128,840 invertebrate species in Brazil alone <ref name = "Lewinsohn 2005">Lewinsohn T. M.and Prado P.I. 2005. How Many Species Are There in Brazil? Conservation Biology. Volume 19 (3), 619</ref>.
The diversity of plant species is the highest on earth with some experts estimating that one square kilometre may contain over 75,000 types of trees and 150,000 species of higher plants Template:Citation needed. One square kilometre of Amazon rainforest can contain about 90,000 tons of living plants. This constitutes the largest collection of living plants and animal species in the world. One in five of all the birds in the world live in the rainforests of the Amazon Template:Citation needed. To date, an estimated 438,000 species of plants of economic and social interest have been registered in the region with many more remaining to be discovered or cataloged Template:Citation needed. (Note: Brazil has one of the most advanced laws to avoid biopiracy, but enforcing it is a problem.)
Deforestation
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Deforestation is the conversion of forested areas to non-forested areas. More than one fifth of the Amazon Rainforest has already been destroyed Template:Citation needed, and the forest which remains is threatened. In a span of just ten years between 1990 and 2000, the total area of forest lost in the Amazon rose from 41.5 million hectares to 58.7 million hectares - an area twice the size of Portugal, with most of the lost forest becoming pasture for cattle <ref name = CIFOR2004> Centre for International Forestry Research (CIFOR) (2004) Beef exports fuel loss of Amazonian Forest. CIFOR News Online, Number 36. </ref>. In 1996, the Amazon was reported to have shown a 34 per cent increase in deforestation since 1992 Template:Citation needed.
In Brazil, the Instituto Nacional de Pesquisas Espaciais - (National Institute of Space Research, or INPE) produces deforestation figures annually. Their deforestation estimates are derived from 100 to 220 images taken during the dry season in the Amazon by the Landsat satellite, and only consider the loss of the Amazon rainforest biome – not the loss of natural fields or savannah within the rainforest. According to INPE, the original Amazon rainforest biome in Brazil of 4,100,000 km2 was reduced to 3,403,000 km2 by 2005 – representing a loss of 17.1% <ref name = “INPE 2005”> . National Institute for Space Research (INPE) (2005). The INPE deforestation figures for Brazil were cited on the WWF Websitein April 2006.</ref>.
A new report by a Brazilian congressional committee says the Amazon is vanishing at a rate of 52,000 square kilometers per year (20,000 miles² per year), over three times the rate for which the last official figures were reported in 1994 Template:Citation needed.
Carbon dynamics
Image:Air roots in the Amazon.jpg Not only are environmentalists concerned about the loss of biodiversity which will result from destruction of the forest, they are also concerned about the release of the carbon contained within the vegetation, which could accelerate global warming.
Amazonian evergreen forests account for about 10% of the world's terrestrial primary productivity and 10% of the carbon stores in ecosystems <ref name="Melillo">Melillo, J.M., A.D. McGuire, D.W. Kicklighter, B. Moore III, C.J. Vörösmarty and A.L. Schloss. 1993. Global climate change and terrestrial net primary production. Nature 363:234–240.</ref> — on the order of 1.1 x 1011 metric tonnes of carbon <ref name ="Tian">Tian, H., J.M. Melillo, D.W. Kicklighter, A.D. McGuire, J. Helfrich III, B. Moore III and C.J. Vörösmarty. 2000. Climatic and biotic controls on annual carbon storage in Amazonian ecosystems. Global Ecology and Biogeography 9:315–335.</ref>. Amazonian forests are estimated to have accumulated 0.62 ± 0.37 tonnes of carbon per hectare per year between 1975 and 1996 <ref name ="Tian"/>. Fires related to Amazonian deforestation have made Brazil one of the top greenhouse gas producers. Brazil produces about 300 million metric tonnes of carbon dioxide a year; 200 million of these are come from logging and burning in the Amazon Template:Citation needed.
Conservation
Some environmentalists commonly stress the fact that there is not only a biological incentive to protecting the rain forest, but also an economic one. One hectare in the Peruvian Amazon has been calculated to have a value of $6820 if intact forest is sustainably harvested for fruits, latex, and timber; $1000 if clear-cut for commercial timber (not sustainably harvested); or $148 if used as cattle pasture.<ref name ="Peters">Peters, C.M., Gentry, A.H. & Mendelsohn, R.O. (1989) Valuation of an Amazonian forest. Nature 339: 655-656.</ref> The assumptions of this study have been widely challenged however.
The Força Aérea Brasileira has been using EMBRAER R-99 surveillance aircraft, as part of the SIVAM program, to monitor the forest. At a conference in July 2004, scientists warned that the rainforest will no longer be able to absorb the millions of tons of greenhouse gases annually, as it usually does, because of the increased pace of rainforest destruction. 9,169 square miles of rain forest were cut down in 2003 alone.
In Brazil alone, more than 90 indigenous tribes have been destroyed by European colonists since the 1900s, and with them have gone centuries of accumulated knowledge of the medicinal value of rainforest species. As tribal homelands continue to be destroyed by deforestation, native rainforest tribes continue to disappear.
Response to climate change
There is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21k years through the last glaciation (LGM) and subsequent delaciation. Analyses of sediment deposits from Amazon basin paleolakes and from the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover in the basin<ref name="Colinvaux1">Colinvaux, P.A., De Oliveira, P.E. 2000. Palaeoecology and climate of the Amazon basin during the last glacial cycle. Wiley InterScience. (abstract)</ref>. There is debate, however, over how extensive this reduction was. Some scientists argue that the rainforest was reduced to small, isolated refugia separated by open forest and grassland<ref name="VanDerHammen">Van der Hammen, T., Hooghiemstra, H.. 2002. Neogene and Quaternary history of vegetation, climate, and plant diversity in Amazonia. Elsevier Science Ltd. (abstract)</ref>; other scientists argue that the rainforest remained largely intact but extending less far to the North, South and East than is seen today <ref name="Colinvaux2">Colinvaux, P.A., De Oliveira, P.E., Bush, M.B. 2002. Amazonian and neotropical plant communities on glacial time-scales: The failure of the aridity and refuge hypotheses. Elsevier Science, Ltd. (abstract)</ref>. This debate has proved difficult to resolve because the practical limitations of working in the rainforest mean that data sampling is biased away from the centre of the Amazon basin, and both explanations are reasonably well supported by the available data.
One computer model of future climate change due to greenhouse gas emissions shows that the Amazon rainforest could become unsustainable under conditions of severely reduced rainfall and increased temperatures, leading to an almost complete loss of rainforest cover in the basin by 2100 [1] <ref name="Radford">Radford, T. 2002. World may be warming up even faster. The Guardian.</ref>. However, simulations of Amazon basin climate change across many different models are not consistent in their estimation of any rainfall response, ranging from weak increases to strong decreases <ref name="IPCC">Houghton, J.T. et al. 2001. Climate Change 2001: The Scientific Basis. Intergovernmental Panel on Climate Change.</ref>. The result indicates that the rainforest could be threatened though the 21st century by climate change in addition to deforestation.
See also
References
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- Sheil, D. and S. Wunder. 2002. The value of tropical forest to local communities: complications, caveats, and cautions. Conservation Ecology 6(2): 9. [2]ar:غابات الأمازون
es:Selva Amazónica fr:Forêt amazonienne he:יער האמזונאס nl:Amazone-regenwoud no:Regnskogen i Amazonas pl:Amazonia pt:Floresta Amazônica fi:Amazon (sademetsä) sv:Amazonas