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Transcript
Deforestation in the Amazon:
Effects on
Climate Change
GG 612 – Global Climate Change
October 31, 1999 – Prof. Myneni
Ashley L. Vandegrift
Forests are most often defined as ecosystems with a minimum of 10% crown cover of
trees and/or bamboo, generally associated with wild flora, fauna and natural soil conditions and
not subject to agricultural practices.1 The changing area of the world’s forests, including natural
forests and forest plantations, was estimated to be 3,454 million hectares in 1995, or about onefourth of the land area of the Earth. (see Chart 1) About 55% of these are located in developing
countries.2 (see Chart 2) While tropical forests occupy less than 7% of the earth’s terrestrial
surface, they are home to as many as 30 million species of plants and animals, or more than half
of all life forms on our planet. 3 Their importance is thus undeniable. For example, of the
roughly 3,000 plants identified as having cancer-fighting properties, 70% grow in the rainforest.
In addition, a single acre of tropical rainforest supports between 60 and 80 tree species. 4 Of these
forests, the Brazilian Amazon is the largest contiguous region of tropical forest in the world,
making it an extremely important global resource, which is sensitive to land-use changes and
destruction. The rate and future course of these land-use changes, or forest clearing, in the
Brazilian Amazon is closely linked to human-use systems that replace the vegetation.
Deforestation often refers to a change in land-use with the depletion of tree crown cover to less
than 10%.5 More specifically, deforestation is the complete destruction of forest cover through
clearing for agriculture, cattle ranching, small holder agriculture, large-scale commodity crop
production and logging. Further, forest degradation through less-than-destructive logging, forest
land farming and fuelwood gathering is estimated to amount to more than the area of
deforestation, working to lower forests’ overall productive capacity. As global deforestation rates
have continued to soar, causing rapid and potentially severe impacts, so have concerns of how
this process effects other natural cycles. Forests are the single most important repository of
terrestrial biological diversity, as well as home to many animals and indigenous peoples.
Deforestation causes a loss of this biodiversity and habitat, as well as disrupts the natural carbon
cycle. Most importantly, it is the release of CO2 into the atmosphere due to deforestation, which
has in turn, led to an increase in climate change in regions distant from the perturbed area.
Amazonian deforestation rates are now used to determine human effects on the global carbon
cycle. Thus, climate change is becoming one of the most serious effects of large-scale
deforestation in the Amazon.
The global carbon cycle is made up of many carbon flows and stocks, proving that the
interactions between land surface and the atmosphere are significant and complex. Natural stocks
include oceans, fossil fuel deposits, the atmosphere, and the Earth itself when the element is
present in rocks and sediments, swamps, wetlands, forests and soils. Hundreds of billions of tons
of carbon as CO2 is absorbed from, or emitted to, the atmosphere through natural processes.
2
These flows include plant photosynthesis, respiration and decay, as well as oceanic absorption
and release of CO2. Currently, the atmosphere contains about 750 billion tons of carbon. (see
Chart 3) This amount is the result of an increase by about 25% in the past 100 years, or an
increase of about 1.5 ppm per year. 6 Further, the whole Amazonian hylaea retains about
115 * 109 tons of carbon. This is of the order of nearly 20% of the carbon of the entire
atmosphere’s CO2. If the entire Amazon forest was replaced by a much less voluminous, manmade vegetation, there would be a net increase of about 8% in global atmospheric CO2 levels.7
CO2, an important greenhouse gas, forms when the carbon in biomass oxidizes as it burns or
decays. This is mostly due to human activities that alter land-uses and fossil fuel combustion.
Land-use changes include slash-and-burn agriculture; clearing land for permanent pasture,
cropland or human settlements; the development of infrastructure, such as roads and dams;
intentional and accidental forest burning; and unsustainable logging and fuelwood collection.
Land-use changes thus cause both carbon sinks and sources. A stock that is taking up carbon is a
sink. For example, forests accumulate carbon over decades and centuries. About two-thirds of
the globe’s terrestrial carbon, exclusive of that sequestered in rocks and sediments, is sequestered
in the standing forests, forest plants, leaf and forest debris, and in forest soils.8 A stock that is
releasing carbon is a source of emissions, and if enough carbon is released, the forest will
eventually become a net source. The release of CO2 will occur if the original ecosystem stored
more carbon than the modified ecosystem, thus, causing deforestation to act as a source of CO2.
Further, the amount of carbon released is a result of deforestation at different rates according to
the method of clearance and subsequent land-use. (see Chart 4) Throughout the 1980’s, it is
believed that deforestation accounted for 1.6 billion tons of carbon emissions. 9 If forests are
simply cut and allowed to decay, then most of the carbon is released into the atmosphere within
ten to twenty years. This release is the forest’s most important contribution to climate change,
even though human activities in tropical forests also produce other greenhouse gases, such as
methane, carbon monoxide, nitrous oxide and ozone, which can act as sources as well. One of
the main differences between CO2 and these other gases is that newly added CO2 will remain in
the atmosphere from decades to thousands of years, while the others will breakdown much faster.
It is now widely believed that the accumulation of CO2 in the atmosphere, partly due to
deforestation, is responsible for the observed global warming of around 0.5°C in the past 100
years.10
Global warming is now attributed to the steady increase of atmospheric trace gases
produced largely by human activities. These gases are referred to as “greenhouse gases” because
they cause radiative forcing, by letting in most of the incoming solar radiation that heats the
3
Earth’s surface, yet also prevent the outgoing thermal radiation from escaping to space, thus
trapping some of the surface heat energy. Aerosols also contribute to climate change. Most
aerosols reflect solar radiation back to space, working to cool the earth’s surface. Although
aerosols are injected into the atmosphere from natural sources, their concentration can also be
increased by human activities such as deforestation and over-grazing, which emit dust from the
top soil into the air. The concentration of greenhouse gases, especially CO2, has fluctuated
naturally over geological time scales. The temperature of the Earth has responded to these
fluctuations by switching between ice age and interglacial conditions. In addition to these slow
natural variations, atmospheric concentrations of greenhouse gases can be altered by the burning
of fossil fuels, clearing of forests, and many other industrial activities. Human activities can
produce a change in atmospheric composition, thus leading to radiative forcing of the climate
system and an eventual change in climate. While much of the existing climate change may be
due to these natural variations, it is now widely believed that the current trends are actually due to
these anthropogenic causes. For example, for the first time ever, the Intergovernmental Panel on
Climate Change has concluded that the observed increase in global average temperature over the
last century “is unlikely to be entirely natural in origin” and that “the balance of evidence
suggests that there is a discernible human influence on global climate.”11 It has been measured
that the globally averaged temperature of the air at the Earth’s surface has warmed between 0.3°
and 0.6°C since the late 19th century.12 (see Chart 5) Further, all 10 of the warmest years on
record have occurred in the last 15 years, while the 1990s have already been warmer than the
1980s by almost 0.1°C. 13 The warming has been greatest at night, over land, in the mid-to-high
latitudes of the northern hemisphere, while the warming during the northern winter and spring has
been stronger than during other seasons. Other evidence of global warming since the 19th century
include the observed rise in sea level, the shrinkage of mountain glaciers, a reduction of northern
hemisphere snow cover, and increasing sub-surface ground temperatures. Much support for this
evidence rests on measurements from tree rings, ice cores, and corals. It is expected that mean
surface temperature of the earth will most likely rise by 1° to 2°C over the next 50 to 100 years, if
current CO2 trends continue. 14 Because CO2 changes can drive climate change, it is important to
examine those activities which effect CO2 levels. Due to the fluctuations in carbon resulting from
land-use changes, deforestation has become a major cause of present and future climate change.
In turn, these climate changes could also effect sea level; damage human health; increase the
frequency of extreme events such as hurricanes and El Nino; alter the productivity of plants and
agriculture; put severe stress on forests, wetlands and other natural habitats; cause the expansion
of the earth’s deserts; and melt polar ice caps.
4
Forest resources assessments provide information on forest extent and location, types,
condition, wood volume and biomass. They are carried out on a sub-national, national, regional
and global level. Increasingly, satellite data has been used to measure the affects of deforestation
and thus it’s influences on the carbon cycle and climate change. The use of this tool is very
important, as it documents the most extreme form of land-use, over large areas, and at low cost.
Development of satellite image-mapping projects are becoming more widespread as the critical
effects of deforestation are becoming more well-known. Forest conversion to agriculture is often
monitored from space using imagery from the Landsat Thematic Mapper satellites.
Unfortunately, this approach fails to include those forest alterations that reduce tree cover, but do
not eliminate it. One such satellite project used satellite imagery covering the forested portion of
the Amazon Basin to measure deforestation and the resulting forest fragmentation and edge
effects. This project used both satellite data and GIS (Geographic Information Systems) to
stratify the Amazon on the basis of cover types. GIS provides a data management tool for
combining large amounts of spatial data and merging the information to create one large map of
the area. This particular study included the “Legal Amazon”, made up of many states in the
Amazon basin: Acre, Amapa, Amazonas, Para, Rondonia, Roraima, Mato Grosso, Maranhao, and
Tocantins. The data included 210 black and white photographic images of the Brazilian Amazon,
which were used to create a map of the deforestation and influence on forest fragmentation and
habitat degradation. Using a scale of 1:500,000, visual deforestation and standard vector GIS
techniques were used to create this single map. The digitized scenes were projected into equalarea geographic coordinates, edge matched and merged to form a single, seamless data set of the
entire Amazon. These images include mining operations, airfields, visible roads, power lines, and
other similar human-made features, which were digitized into GIS and treated as deforestation. It
is projects such as this which have provided much of the current information on deforestation. As
with all scientific studies, there is great uncertainty in the results, specifically, with the extent and
rate of deforestation. One such uncertainty includes the fact that there are highly variable
differences between the data from this study and others previously made. These differences are a
result of three major factors: different stratification of forest, cerrado and water; slightly different
estimates of secondary forest growth; and a difference in positional accuracy, interpretation and
boundary generalizations. As far as satellite data is concerned, remote sensing techniques also
offer conflicting estimates depending on resolution and sampling coverage. Further, the rates of
deforestation have not been directly measured over time as part of agriculture or land-use
censuses, thus causing a lack of historical data. In the South American tropics, instrumental
records of climate do not extend very far into the past, adding to the uncertainty. In terms of
5
global warming, the range of estimated warming of 1° to 2°C in the next 50 to 100 years, for
example, arises from uncertainties about the response of climate to the buildup of greenhouse
gases and particles, as well as the total amount of future emissions of these gases. Factors such as
estimates of human population growth, land use changes, life styles, and energy choices yield a
range of plausible greenhouse gas emissions. Unfortunately, this prevents the comparison of
different deforestation and climate change studies.
Deforestation occurs when forestland is cleared and reforestation does not take place.
There are two fundamental forces giving rise to deforestation. First, competition between
humans and non-humans for the remaining ecological niches on land and in coastal regions. In
turn, this competition reflects the rapidly expanded population growth of developing countries.
Second, the “failures” in the workings of the international and national economic systems.
“Failures” mean the failure of economic systems to reflect the true value of environmental
systems in the workings of the economy. For example, many functions of tropical forests are not
marketed. Further, decisions to convert tropical forests are encouraged by fiscal and other
incentives for various reasons. One of the major direct causes of deforestation is the clearing of
land for other uses such as agriculture, while the greatest loss of carbon in forest ecosystems
involves the change of land-use from primary closed forest to permanent agriculture. Human uses
of tropical forests vary greatly in their ecological impacts. Other major causes of deforestation in
the Amazon are logging; rubber tapping; cattle ranching; forest conversion to cash-crop
plantations, such as oil palm and rubber; forest destruction for roads, mining, and other activities;
slash-and-burn farmers; development programs involving resettlement and infrastructure; and
wildfires and other natural phenomenon such as drought. Of these causes, logging, fires and
drought are among the greatest. It is believed that current estimates of deforestation, which often
fail to include these phenomenon, capture less than half of the forest area that is impoverished
each year, and even less during severe droughts. Loggers do not clear-cut and burn as with
agriculture, but fragment forests by harvesting or damaging the trees. Rubber tapping only uses
the forest at very low intensity through the harvest of animals, fruits, latex and other non-timber
products, but has a serious impact. The climatic and ecological consequences of deforestation in
the Brazilian Amazon are among today’s leading environmental concerns, due to the contribution
of CO2 emissions into the atmosphere and the decreases in biodiversity and soil productivity.
Deforestation is ultimately caused by human use systems that replace the forest.
However, the indirect causes and assessments of deforestation are not as clear. Some of the roots
of these causes are as follows: population growth, urbanization, agricultural trends, land-tenure
policies, development of infrastructure, expansion of cash crops, government and land-use plans,
6
extension programs, public perceptions and lack of knowledge of forest resources, energy needs
and laws and regulations. There is no question as to the immediate results of human degradation
on forests, and now many of the long term consequences involving climate change, but the
question of why humans deplete forest resources has often been under scrutiny. In developing
countries such as Brazil, deforestation is a result of subsistence agriculture and opportunities to
advance economically by utilizing a “free” natural resource. But, why has this occurred? One of
the first answers is population growth, which itself is not a direct cause of deforestation, but is
definitely related. The Malthusian explanation for tropical deforestation is that “surplus people”
are heading for the developing world’s agricultural frontiers in “droves”.15 This domestic
demand for agricultural commodities has been rising because the number of consumers has been
constantly multiplying with high population growth rates and extensive migration. Between 1950
and 1990, the Latin American population just about tripled, from 166 million to 448 million. 16
One third of this increase was in Brazil. Thus, demographic pressures in rural areas have been
superimposed on skewed land distributions, poverty, inadequate health and educational services,
poor infrastructure and lack of access to agricultural technology. Under these conditions,
governments frequently encourage migration to frontier areas to deflect pressures in cities.
Unfortunately, the prospects for containing Brazilian frontier expansion are doubtful as current
populations are overwhelmingly young, and those living in or near tropical forests will utilize
land, fuel and shelter for as long as the forests last. As the numbers of people needing to be fed
increases, pressures on natural resources will undoubtedly mount. Further, most people in the
Brazilian Amazon respond to these opportunities for food and shelter, as well as to capture
sizable rents, through agricultural and lumber production, by “cutting and running”. Slash and
burn cultivators rarely practice a rotary form of agriculture, which imposes great pressures on
forest fringes, as they clear extensive areas before driving deeper into the forest year after year.
This further exacerbates the problem, as sustainable use of forest resources becomes a distant
reality.
Little migration to frontier areas of tropical forests take place without roads. As
population increases and primary tropical forest is destroyed, settlement and subsequent clearance
of forest is closely followed by the expansion of a road network. This then allows for even more
deforestation. It has been argued that this type of infrastructure development is the single-most
powerful element in the deforestation of frontier areas. These effects of road building have been
greatly felt in the Brazilian Amazon. The population increase in the zone of influence of the
region’s first interregional highway (completed in the mid-1960s) is estimated to have been
between 300,000 and 2,000,000 during the 1970s. For example, the number of migrants in the
7
Amazon region of Rodonia more than doubled annually after the state’s main highway was paved
in the early 1980s. 17 In both of these cases, the surge in migration following road construction
was followed by massive deforestation. It can be assumed that since this time, infrastructure
development has only increased, thus adding more pressure on the forests. In many areas,
traditional shifting cultivation has been taken over by the wholesale removal of vast tracts,
prompted by highway development and economic incentives for large agricultural projects, large
cattle ranchers, small scale farming colonization and logging. In more economic terms,
specialization has increased in the production and export of agricultural commodities in which the
Brazilian Amazon region holds a comparative advantage. Whether this be for agricultural
commodities, or fuel for timber export or charcoal production, commercial and cash crop motives
have led to serious forest degradation. Consequently, a rise in domestic or international demand
for agricultural goods has led to an outward shift in the region’s extensive margin. This high
economic value that has been placed on the Amazon’s resources have in turn resulted in vast
deforestation. At this point in time, it seems most likely that the technology that would be needed
for a sound response to the mounting demand for agricultural commodities will not be enough to
spare the Amazon’s natural habitats. Further, the relatively rare secure land titles in these tropical
forests continue to create “open access” areas, facilitating this economic expansion. The situation
has become even worse with the onslaught of foreign companies realizing the potential monetary
gains from utilizing the Brazilian Amazon’s vast forest resources.
Between 1980 and 1995, the extent of the world’s forests decreased by about 180 million
hectares. There was a net increase of 20 million hectares in developed countries, but a net loss of
200 million hectares in developing nations. (see Chart 6) Between 1990 and 1995, developing
countries lost 65.1 million hectares of forest.18 (see Chart 7) In the past twenty years alone, 50%
of the original Amazon forests have been lost due to agricultural expansion.19 The destruction of
the Brazilian Amazon reached an all-time high in 1995, when over 11,000 square miles, an area
larger than New Jersey, were destroyed. 20 Further, the FAO estimated that the change in forest
cover caused a loss of some 2.7 billion metric tons of biomass between 1980 and 1990.21
Although the global loss of forests was still very high during this period, the overall figures
suggest that the rate of deforestation may be slowing. For example, it is expected that forest loss
in tropical Latin America will drop from 918.1 million ha in 1980 to 119 million ha in 2020.22
(see Chart 8) The current situation is still bleak. It is estimated that 10,000 to 15,000 km2 of
undisturbed forest were logged per year in 1996 and 1997, affecting an area that was 50% to 90%
the size of the area that was completely deforested in 1996.23 More recently, by mid-1998, low
rainfall in much of the Amazon attributed to El Nino contributed to a prolonged fire season, and
8
thus, further degradation. In 1997, over 2 million hectares of rain forest in Brazil burned due to
fires set by farmers and ranchers to clear old cattle pasture and burn newly cut forest which
subsequently burned out of control. Some areas in the Brazilian Amazon are experiencing a
secondary growth recovery, but unfortunately, the forest’s stature and biomass, and thus the
ability to store carbon, in these areas is still less than in primary forests.
The role of forests in carbon sequestration is very well understood and offers one of the
greatest near-term potentials for management as a sink. Fortunately, deforestation is subject to
control and influence at many points. The use of forests by people dwelling in or adjacent to
them for productive, non-productive, and symbolic and cultural purposes is a principal factor in
determining a strategy for sustainable utilization. Most importantly, the value of conserving the
forest relative to deforestation and alternative land-uses must be enhanced. Mechanisms to
sustain forests range from protecting intellectual property rights on products developed from
materials originating in the forests, to restricting widespread access into the forests, to
maximizing the value of non timber forest products. In economic terms, these strategies will, in
turn, make forests more of a public good. On the policy end, it is important to discourage farmers
and ranchers from adopting production-enhancing measures, by strengthening land tenure or
lengthening commercial forest concessions to promote replanting. Adding to the planet’s net
carbon stores in vegetative cover or soil and preventing net loss will help to moderate global
warming by keeping atmospheric levels of CO2 lower than they would otherwise be. In terms of
the carbon cycle, carbon that could be released through deforestation can be kept out of the
atmosphere through a few land-use approaches: slowing or stopping the loss of existing forests to
preserve current carbon reservoirs, while adding to the planet’s vegetative cover through
reforestation to enlarge living terrestrial carbon reservoirs; increasing the carbon stored in nonliving carbon reservoirs such as agricultural soils; increasing the carbon stored in artificial
reservoirs, including timber products; and substituting sustainable biomass energy sources for
fossil fuel consumption, thus reducing energy-related carbon emissions. Therefore, by
sustainably managing natural forests to yield economic benefits, by making exploitative activities
such as logging more efficient, improving the productivity of agricultural land to reduce pressure
on remaining forests and making logging more efficient, climate change could ultimately be
curbed.
Amazonian deforestation is a serious problem with global consequences. Not only does
the destruction of these tropical forests disrupt biological diversity and other land uses, but it is
now believed that the removal of this vital terrain is contributing to the accumulation of CO 2 in
the atmosphere. Long term results of this phenomenon are now linked to climate change and
9
global warming. In some cases, the remaining vast areas of undisturbed forest in the Amazon
lead to the mistaken conclusion that deforestation is really only a minor concern. This is not true.
The use of Landsat Mapper satellites now estimate deforestation rates more realistically, helping
to predict overall rates of forest disturbance and the resulting effects on CO2 changes.
Amazonian deforestation may begin as a local problem, disrupting native lifestyles and
biodiversity, but research has proven that deforestation has turned into both a regional and global
problem. Climate change is ultimately one of the worst environmental problems that humans are
now faced with. What makes it worse, is that many of these negative results are due to human
activities. Therefore, it is important that change now begin with the alteration of these activities.
If not, resulting climate change will in turn disrupt even more natural cycles. A warmer earth will
speed up the water cycle, interrupting the exchange of water among the oceans, atmosphere and
land; higher temperatures could cause more evaporation, drying out soils at a faster rate;
increased amounts of water in the atmosphere could mean more rain or snow overall; global mean
sea level could continue to rise and flood many coastal areas. And these are just a few of the
consequences of continued use of fossil fuels and deforestation. The earth is an interactive being,
as one change will in turn effect many other natural processes. In the case of deforestation, this is
best exemplified by the fact that the burning of trees in the Amazon can cause changes in
temperature which will reach the other side of the earth. There are still many unknowns, but what
has been proven, should be enough to trigger efforts to halt what we know now will create a
bleaker situation in the future.
10
Endnotes
1
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 8.
2
FAO. “The State of the World’s Forests 1999.”
3
David Skole and Compton Tucker. “Tropical Deforestation and Habitat Fragmentation in the
Amazon: Satellite Data from 1978 to 1988.”
4
James F. Kasting. “Tropical Rainforest Facts.” Natural Resources Defense Council.
5
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 8.
6
US Global Change Research Information Office. “The Carbon Cycle, Climate, And The
Long-Term Effects Of Fossil Fuel Burning.”
7
Daniel C. Nepstad, et al. “Large-scale impoverishment of Amazonian forests by logging and
fire.” Nature (April 8, 1999): 505-508.
8
Roger A. Sedjo, Brent Sohngen and Pamela Jagger. “Carbon Sinks in the Post-Kyoto World.”
Resources For The Future-Internet Edition-Climate Issue Brief #12, 1998.
9
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 3.
10
Fung, Inez. “Oh Where Oh Where Does the CO2 Go?” NASA Goddard Institute for Space
Studies.
11
Union of Concerned Scientists. “Global Warming.”
12
US Global Change Research Information Office. “Has the World Warmed?”
13
Union of Concerned Scientists. “Global Warming.”
14
US Global Change Research Information Office. “The Carbon Cycle, Climate, And The
Long-Term Effects Of Fossil Fuel Burning.”
15
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 135.
16
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 159.
17
Katrina Brown and David W. Pearce, ed., The Causes of Tropical Deforestation. (British
Columbia, 1994), 162.
18
FAO. “The State of the World’s Forests 1999.”
19
Daniel C. Nepstad, et al. “Large-scale impoverishment of Amazonian forests by logging and
fire.” Nature (April 8, 1999): 505-508.
11
20
James F. Kasting. “Tropical Rainforest Facts.” Natural Resources Defense Council.
21
Sten Nilsson. “Do We Have Enough Forests?” International Union of Forestry Research
Organizations.
22
Sten Nilsson. “Do We Have Enough Forests?” International Union of Forestry Research
Organizations.
23
H. Sioli. “The Effects of Deforestation in Amazonia.” In The Human Impact Reader, ed.
Andrew Goudi, 360.
12
Bibliography
1. Brown, Katrina and David W. Pearce, ed. The Causes of Tropical Deforestation. British
Columbia: 1994.
2. Dickenson, Robert E., ed. The Geophysiology of Amazonia. New York: John Wiley & Sons,
1987.
3. FAO. “The State of the World’s Forests 1999.” http://www.fao.org.
4. Fung, Inez. “Oh Where Oh Where Does the CO2 Go?” NASA Goddard Institute for Space
Studies. http://www.giss.nasa.gov/research/intro/fung.01/.
5. Kasting, James F. “Tropical Rainforest Facts.” Natural Resources Defense Council.
http://www.nrdc.org/triv/rainf.html.
6. Ma, Quancheng. . “Greenhouse Gases: Refining the Role of Carbon Dioxide.” NASA
Goddard Institute for Space Studies. http://www.giss.nasa.gov/research/intro/ma.01/.
7. Nepstad, Daniel C., et al. “Large-scale impoverishment of Amazonian forests by logging and
fire.” Nature (April 8, 1999): 505-508.
8. Nilsson, Sten. “Do We Have Enough Forests?” International Union of Forestry Research
Organizations. http://iufro.boku.ac.at/iufro/publications/dowehave.htm#sensetivitlanduse.
9. Sedjo, Roger A., Brent Sohngen and Pamela Jagger. “Carbon Sinks in the Post-Kyoto
World.” Resources For The Future-Internet Edition-Climate Issue Brief #12, 1998.
10. Sedjo, Roger A. “Harvesting the Benefits of Carbon ‘Sinks’.” Resources (Fall 1998): 10-13.
11. Sioli, H. “The Effects of Deforestation in Amazonia.” In The Human Impact Reader, ed.
Andrew Goudi, 356-363.
12. Skole, David and Compton Tucker. “Tropical Deforestation and Habitat Fragmentation in the
Amazon: Satellite Data from 1978 to 1988.”
http://www.bsrsi.msu.edu/overview/papers/science1/.
13. Union of Concerned Scientists. “Global Warming.”
http://www.ucsusa.org/warming/warm-home.html.
14. US Global Change Research Information Office. “Has the World Warmed?”
http://www.gcrio.org/ipcc/qa/02.html#fig1.
15. US Global Change Research Information Office. “The Carbon Cycle, Climate, And The
Long-Term Effects Of Fossil Fuel Burning.”
http://www.gcrio.org/CONSEQUENCES/vol4no1/carbcycle.html.
16. World Resources Institute. “Mitigating climate change through forest management.”
http://www.wri.org/climate/mitigate.html.
13
CHART 1
Total Forest 1990 & 1995 (1000 ha)
3,500,000
1990
1995
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0
Brazil
Tropical South America
Source: FAO "State of the World's Forests 1997"
World
CHART 2
Forest areas by main regions in 1995
Latin America,
Caribbean
27.5%
North America
13.2%
Africa
15.1%
Europe
27.0%
Asia/Oceania Developed
3.0%
Source: FAO "State of the World's Forests 1999"
Asia/Oceania Developing
14.2%
CHART 3
The World's Carbon Reserves (GtC)
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
Atmosphere
Forests
Soils
Surface
Ocean
Coal
Oil
Natural Gas
Source: www.gcrio.org, "The Carbon Cycle, Climate, And The Long-Term Effects of Fossil Fuel Burning"
CHART 4
Changes in carbon with land-use conversion
Closed primary
Closed secondary
Open forest
Original
Shifting Permanent
Carbon Agriculture Agriculture
283
-204
-220
194
-106
-152
115
-36
-52
Source: Brown & Pearce, 1994
Pasture
-220
-122
-52
80
60
40
20
0
-20
-40
-60
1872
1878
1884
1890
1896
1902
1908
1914
1920
1926
1932
1938
1944
1950
1956
1962
1968
1974
1980
1986
1992
1998
CHART 5
Global Temperature Anomalies (0.01 C)
Source: GHCN 1701-08/1999
1866
CHART 6
Forest Area in 1995 as Compared with 1980
(% of 1980 forest area)
6
4
2
0
-2
-4
-6
-8
-10
Source: FAO "State of the World's Forests 1999"
Developing
World
Latin America,
Caribbean
Africa
Developing
Asia/Oceania
Developed
World
Australia,
Japan, New
Zealand
North America
Europe
-12
CHART 7
Total Forest Change 1990 to 1995 (1000 ha)
World
Tropical South America
Brazil
-60,000
-50,000
-40,000
-30,000
Source: FAO "State of the World's Forests 1999"
-20,000
-10,000
0
CHART 8
Accumulated Losses in Tropical Forests from 1990 to 2050
(million ha)
2,000
1990
1,800
2020
2025
1,600
1,400
1,200
1,000
800
600
400
200
0
Tropical Africa
Tropical Asia
Tropical Latin
America
Source: International Union of Forestry Research Organizations
Total