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Amazon Rainforest
From Wikipedia, the free encyclopedia
Map of the Amazon rainforest ecoregions as delineated by the WWF. Yellow line
encloses the Amazon rainforest. National boundaries shown in black. Satellite image
from NASA.
River in the Brazilian Amazon Rainforest.
The Amazon Rainforest (Brazilian Portuguese: Floresta Amazônica or Amazônia;
Spanish: Selva Amazónica or Amazonía) is a moist broadleaf forest in the Amazon
Basin of South America. The area, also known as Amazonia or the Amazon Basin
encompasses seven million kilometers (1.2 billion acres), though the forest itself
occupies some 5.5 million kilometers, located within nine nations: Brazil (with 60
percent of the rainforest), Colombia, Peru, Venezuela, Ecuador, Bolivia, Guyana,
Suriname, and French Guiana. States or departments in four nations bear the name
Amazonas after it. The Amazon represents over half of the planet's remaining
rainforests and comprises the largest and most species-rich tract of tropical rainforest in
the world.
Etymology
The name Amazon is said to arise from a battle which Francisco de Orellana had with a
tribe of Tapuyas where the women of the tribe fought alongside the men, as was the
custom among the entire tribe. Another theory credits the name to Orellana mistaking
indigenous men wearing "grass skirts" as women. Orellana derived the name Amazonas
from the ancient Amazons of Asia and Africa described by Herodotus and Diodorus in
Greek legends.
Biodiversity
The Amazon River flowing through the rainforest
Deforestation in the Amazon Rainforest threatens many species of tree frogs, which are
very sensitive to environmental changes (pictured: Red-eyed Tree Frog)
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.[1]
As the largest tract of tropical rainforest in the Americas, the Amazonian rainforests
have unparalleled biodiversity.
The region is home to about 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 fish, 1,294
birds, 427 mammals, 427 amphibians, and 378 reptiles have been scientifically
classified in the region [2]. Scientists have described between 96,660 and 128,843
invertebrate species in Brazil alone.[3]
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.[citation needed] One square kilometre of Amazon rainforest can contain about
90,790 tonnes 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.[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 catalogued.[citation needed]
Deforestation
Deforestation is the conversion of forested areas to non-forested areas. The main
sources of deforestation in the Amazon are human settlement and development of the
land.[4] Between 1991 and 2000, the total area of forest lost in the Amazon rose from
415,000 to 587,000 km² - an area twice the size of Portugal, with most of the lost forest
becoming pasture for cattle.[5]
History of Deforestation in the Amazon
Prior to the early 1960’s, access to the Amazon was incredibly restricted and aside from
partial clearing along rivers the forest remained basically intact.[6] The key point in
deforestation of the Amazon was when the colonists established farms within the forest
during the 1600s. Their farming system was based on crop cultivation and the slash and
burn method. The colonists were unable to successfully manage their fields and the
crops due to the loss of soil fertility and weed invasion[7]. The soils in the Amazon are
productive for just a short period of time, and the farmers are therefore constantly
moving and clearing more and more land[8]. Amazonian colonization was ruled by cattle
raising because ranching required little labor, generated decent profits, and awarded
social status in the community. However the results of the farming lead to extensive
deforestation and caused extensive environmental damage[9]. An estimated 30% of the
deforestation is due to small farmers and the intensity within the area that they inhabit is
greater than the area occupied by the medium and large ranchers who possess 89% of
the Legal Amazon’s private land. This emphasizes the importance of using previously
cleared land for agricultural use, rather the typical easiest political path of distributing
still-forested areas[10]. In the Brazilian Amazon, the amount of small farmers versus
large landholders changes frequently with economic and demographic pressures.[11]
Causes of Deforestation in the Amazon
The annual rate of deforestation in the Amazon region has continued to increase from
1990 to 2003 because of factors at local, national, and international levels.[12] Brazil is
currently the second-largest global producer of soybeans after the United States, and as
prices for soybeans rise, the soy farmers are pushing northwards into forested areas of
the Amazon. As stated in Brazilian legislation, clearing land for crops or fields is
considered an ‘effective use’ of land and is the beginning towards land ownership.[13]
Cleared property is also valued 5-10 times more than forested land and for that reason
valuable to the owner whose ultimate objective is resale. As stated by Michael
Williams,“The people of Brazil have always thought of the Amazon as a communal
possession which they felt free to hack, burn, and abandon at will.”[14] The soy industry
is the principal source of foreign currency for Brazil; therefore, the needs of soy farmers
have been used to validate many of the controversial transportation projects that are
currently developing in the Amazon.[15] The first two highways: the Belém-Brasília
(1958) and the Cuiaba-Porto Velho (1968) were the only federal highways in the Legal
Amazon to be paved and passable year-round before the late 1990’s. These two
highways are said to be “at the heart of the ‘arc of deforestation’,” which at present is
the focal point area of deforestation in the Brazilian Amazon. The Belém-Brasilia
highway attracted nearly two million settlers in the first twenty years. The success of the
Belém-Brasilia highway in opening up the forest was re-enacted as paved roads
continued to be developed unleashing the irrepressible spread of settlement. The
completions of the roads were followed by a wave of resettlement and the settlers had a
significant effect on the forest.[16]
Measured Rates of Deforestation in the Amazon
In 1996, the Amazon was reported to have shown a 34% increase in deforestation since
1992[17]. The mean annual deforestation rate from 2000 to 2005 (22,392 km² per year)
was 18% higher than in the previous five years (19,018 km² per year) [18]. In Brazil, the
Instituto Nacional de Pesquisas Espaciais (INPE, or National Institute of Space
Research) 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, also may 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% [19].
Period
Estimated Remaining
Forest Cover
in the Brazilian Amazon
(sq. km)
Annual
forest
loss (sq.
km)
Percent of
1970
cover
remaining
Total forest
loss
since 1970 (sq.
km)
1970
3,684,675
19701979
3,473,375
21,130
94.3%
211,300
19801989
3,262,075
21,130
88.5%
422,600
1990
3,248,265
13,810
88.2%
436,410
1991
3,237,135
11,130
87.9%
447,540
1992
3,223,349
13,786
87.5%
461,326
1993
3,207,939
15,410
87.1%
476,736
1994
3,193,043
14,896
86.7%
491,632
1995
3,163,984
29,059
85.9%
520,691
1996
3,145,824
18,160
85.4%
538,851
1997
3,132,784
13,040
85.0%
551,891
1998
3,115,944
16,840
84.6%
568,731
1999
3,098,685
17,259
84.1%
585,990
2000
3,078,849
19,836
83.6%
605,826
2001
3,060,719
18,130
83.1%
623,956
2002
3,035,219
25,500
82.4%
649,456
2003
3,011,089
24,130
81.7%
673,586
2004
2,984,960
26,129
81.0%
699,715
2005
2,966,060
18,900
80.5%
718,615
[citation needed]
Future of Deforestation
At the current rate, in two decades the Amazon Rainforest will be reduced by 40%
(National Geographic, January 2007) The 2005-2006 year had a 41% drop in
deforestation, This is the lowest figure since 1991. Deforestation rates are expected to
go down as conservation has been at a very high rate in the past five years. At this rate,
it is possible that the Amazon Rainforest will no longer exist by the end of the century.
Carbon dynamics
Aerial roots of red mangrove on an Amazonian river
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.
The many plants and scenery of the Amazon Rainforest
Amazonian evergreen forests account for about 10% of the world's terrestrial primary
productivity and 10% of the carbon stores in ecosystems [20] — of the order of 1.1 x 1011
metric tonnes of carbon [21]. Amazonian forests are estimated to have accumulated 0.62
± 0.37 tonnes of carbon per hectare per year between 1975 and 1996 [21]. 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 come from logging and burning in the Amazon. Although Brazil is listed as one
of the lowest per capta(rank 124) in CO2 emissions according to the US Department of
Energy's Carbon Dioxide Information Analysis Center (CDIAC) (see List of countries
by carbon dioxide emissions per capita).
Anthropogenic emission of greenhouse gases broken down by sector for the year 2000.
Conservation
Some environmentalists commonly state the fact that there is not only a biological
incentive to protecting the rainforest, 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.[22] However, the
assumptions of this study have been widely challenged.
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, and the increase in the greenhouse gases emision by
industrialized countries. 9,169 square miles of rain forest were cut down in 2003 alone.
In Brazil alone, more than 90 indigenous groups have been destroyed by colonists since
the 1900s, and with them have gone centuries of accumulated knowledge of the
medicinal value of rainforest species. As indigenous territories continue to be destroyed
by deforestation, and ecocide, such as in the Peruvian Amazon[23] indigenous peoples'
rainforest communities continue to disappear, while others, like the Urarina continue to
struggle to fight for their cultural survival and the fate of their forested territories.
Meanwhile, the relationship between nonhuman primates in the subsistence and
symbolism of indigenous lowland South American peoples has gained increased
attention, as has ethno-biology and community-based conservation efforts.
Within the past four years, the conserved land in the Amazon Rainforest has almost
tripled and deforestation rates have dropped up to 60%. About 100 million hectares, or
250 million acres have been put onto some sort of conservation, which adds up to a
current amount of 173 million hectares or 432.5 million acres. [24]
Response to climate change
River in the Amazon rainforest.
There is evidence that there have been significant changes in Amazon rainforest
vegetation over the last 21,000 years through the last glaciation (LGM) and subsequent
deglaciation. 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[25]. 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[26]; other scientists argue that the
rainforest remained largely intact but extending less far to the North, South and East
than is seen today [27]. 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.[28][29] 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 [30]. The result
indicates that the rainforest could be threatened though the 21st century by climate
change in addition to deforestation.
Impact of Amazon drought
In 2005, parts of the Amazon basin experienced the worst drought in 100 years[31], and
there are indications that 2006 could be a second successive year of drought[32]. A 23
July 2006 article in the UK newspaper The Independent reported Woods Hole Research
Center results showing that the forest in its present form could survive only three years
of drought.[33][34] Scientists at the Brazilian National Institute of Amazonian Research
argue in the article that this drought response, coupled with the effects of deforestation
on regional climate, are pushing the rainforest towards a "tipping point" where it would
irreversibly start to die. It concludes that the forest is on the brink of being turned into
savanna or desert, with catastrophic consequences for the world's climate. According to
the WWF, the combination of climate change and deforestation increases the drying
effect of dead trees that fuels forests fires.[35]