March 30th U.S. Global Change Seminar: "Origin, Incidence, and Implications of Amazon Fires"
tsocci at usgcrp.gov
Wed Mar 25 14:46:55 EST 1998
U.S. Global Change Research Program Seminar Series
Origin, Incidence, and Implications of Amazon Fires
What are the past, present, and projected rates of Amazonian deforestation?
What are the principal forces driving deforestation? What role do fires
play in the deforestation of the Amazon? Which parts of the Amazon are
experiencing arid conditions leading to fires? What are the ecological and
social risks of deforestation, now and in the future? How do management
practices affect the health of the Amazon? What role do climate variations
(i.e., El Nino cycles) play in maintaining the health of the Amazon?
Monday, March 30, 1998, 3:15-4:45 PM
New Location: Dirksen Senate Office Bldg., Room 562, Washington, DC
Dr. William T. Sommers, Director of Vegetation Management and Protection
Research, U.S. Department of Agriculture, U.S. Forest Service, Washington,
Dr. Daniel Nepstad, Woods Hole Research Center, Woods Hole, MA
Dr. Compton J. Tucker, NASA/Goddard Space Flight Center, Laboratory for
Terrestrial Physics, Greenbelt, MD
More than 12% of the 2-million square miles of Brazilian Amazonian forest
has been deforested, and converted to crop- and pastureland. In 1995
alone, an area of forest the size of Maryland was cleared and burned. In
addition to this most extreme form of forest alteration, large areas of
Amazonian forest have been selectively logged or burned beneath the canopy,
beyond the view of deforestation mapping exercises. Both deforestation and
forest impoverishment through logging and ground fire greatly increase the
incidence of fire in Amazonia, because these land-use activities replace
the tall, dense, naturally-resistant virgin forests with agricultural lands
and degraded forests that are highly flammable. During the seasonal
drought that affects half of Amazonia, many of these flammable ecosystems
burn. When seasonal drought is very severe, such as during the El Nino
event of 1997/98, even virgin forests become more vulnerable to the ravages
of fire. Hence, a significant portion of the northern Amazonian state of
Roraima has burned in the 97/98 dry season, and continues to burn now, in
March. On a broader scale, the NOAA satellite detected 50% more Amazonian
fires in 1997 than in 1996.
Tropical forests also store large amounts of CO-2, and therefore, play a key
role in regulating the world's climate. Mostly as a result of
deforestation, Brazil now accounts for nearly 10% of the world's greenhouse
gases being emitted into the atmosphere, an amount comparable to many
developed countries. Burning half the Amazon, for example, would release
roughly 35 billion tons of CO-2 into the atmosphere, the equivalent of
approximately 6 years' worth of greenhouse gas emissions for the entire
world. Unfortunately, as a result of land-use influences and practices,
much of the Amazon is also losing its natural capacity to protect itself
from fires, as well as losing its capacity to store carbon and, therefore,
limit future climate warming.
Has the Rate of Deforestation in the Amazon Increased?
Yes. The deforestation rates for the Brazilian Amazon that were recently
released by the Brazilian Space Research Institute (Instituto Brasileiro de
Pesquisas Espaciais - INPE) show that the area of forest cut and burned
nearly doubled from 1994 (15,000 square km) to 1995 (29,000 square km).
In 1996, the rate declined again, to 18,000 square km, and early analysis
indicates that 1997 rates of deforestation were comparable to 1994 rates.
These deforestation rates are much higher however, than the rates reported
in 1992, when only 11,000 square km of forest were cleared each year.
Do These Deforestation Rates Provide an Accurate Description of Human
Impacts on Amazonian Forests?
The INPE deforestation monitoring program provides the most reliable
estimate of the areal extent of forest conversion to agriculture and
ranchland in the Brazilian Amazon, which is the most extreme form of forest
conversion. However, these estimates do not include alterations of the
forest through selective timber harvest and forest groundfire. These
land-use activities impoverish the forest by killing trees and animals, by
releasing carbon dioxide to the atmosphere, and by rendering the forest
more vulnerable to fire. Studies conducted in the field indicate that the
area of forest altered by timber harvest and ground fire may be similar in
size to the area that is deforested during some years.
What is Burning in Amazonia in Addition to Forests?
The Amazon Institute of Environmental Research (Instituto de Pesquisas
Ambientais da Amazonia - IPAM) and the Woods Hole Research Center (WHRC)
conducted a field survey in 1996 of five regions in the Brazilian Amazon
where intensive deforestation and logging have taken place. This study
provides the first detailed analysis of types of burning that are taking
place in the region.
This study indicates that the area of an average property burned each year
ranged from 5% (properties less than 5000 hectares) to 19% (properties
greater than 100 hectares) in 1994 and 1995. Deforestation - the outright
cutting and burning of mature forest - was responsible, on average, for
only 16% of the total burned area, while 73% percent of the burning is on
land that is already deforested and supports pastures, secondary fallow
forests, and other types of non-forest vegetation. Eleven percent of the
burning is beneath the canopy of standing forests. This last type of
burning, which is called forest ground fire, is difficult to monitor using
satellites. During years of intense drought the areal extent of forest
ground fire generally increases dramatically.
What are the Major Ecological Risks Associated with the Burning and
Deforestation of the Amazon?
The virgin forests of Amazonia currently act as giant firebreaks through
the landscape, preventing the spread of fires ignited in pastures and
agricultural clearings. If virgin forests lose this fire break function,
then large Amazonian landscapes will burn periodically, killing
fire-sensitive plants and animals, reducing the amount of biomass stored
in these forests by 10% to 80%, and reducing the amount of water pumped
into the atmosphere - moisture that is necessary to maintain the water and
rainfall cycles. In addition to losing forest cover, fire also destroys
timber and other "useful" plants such as vines (for construction),
medicinal plants, and fruit trees. Each time a forest burns, it becomes
more susceptible to future burning because trees are killed and fuel is
introduced to the forest floor. The major risk from fire is therefore the
conversion of large areas of dense Amazonian forest into savanna-like scrub
What are the Causes of Forest Ground Fires within the Amazon?
Both logging and drought are increasing the flammability of Amazonian
forests. Each year, an area of Amazonian forest is logged that is similar
in size to the area that is deforested (Source: IMAZON). Logging
increases the flammability of these forests by opening up the leaf canopy,
allowing sunlight to penetrate to the fuel layer on the ground, and by
increasing the fuel load through the production of woody debris.
Even virgin forests become flammable when drought is severe. Most forests
in eastern and southern Amazonia (half of the 2 million square miles of
closed canopy forest in Brazilian Amazonia) are subject to severe dry
seasons each year, but grow on deep clay soils that store water which trees
can tap during dry seasons to avoid drought-induced leaf shedding. These
forests are at the "edge" of the rainfall regime that is necessary for them
to be forests, and to resist fire, and are very sensitive to slight
reductions in rainfall. Droughts in Amazonia are most severe during El
Nino Southern Oscillation (ENSO) events, and El Nino's appear to be
increasing in frequency and intensity. The most intense El Nino in
recorded history is taking place right now.
Are There Ways to Reduce the Risk of Fires?
One of the most promising approaches to reducing fires is to prevent or
drastically reduce the number of accidental fires. Half of the area burned
in 1994 and 1995 resulted from accidental fires. Accidental fires resulted
in very large financial losses and extensive environmental damage. For
example, in well-managed cattle pastures, cattle cannot be grazed on burned
pastures until 2 or 3 months into the rainy season. Fires have damaged
fences, killed livestock, burned fruit trees, and threatened human health.
The owners of large ranches (greater than 1000 hectares) in Amazonia invest
an average of more than $2000/year in bulldozing fire breaks to prevent
their pastures and forests from catching fire. Accidental fires cost these
ranchers more than $5000/year in lost grazing and damaged fences. The
owners of small properties (less than 100 hectares) incur proportionate
costs associated with accidental fire.
The 9000-hectare Del Rei community, in eastern Amazonia, has come up with a
very promising local approach to the prevention of accidental fire. This
farm community has implemented its own fire ordinance, which requires
community members to: (1) use fire breaks before they burn in preparation
for agriculture, (2) tell neighbors when they are burning their
agricultural plots, and (3) compensate those neighbors who suffer losses
because of their fires. Reductions in the occurrence of accidental fires
can be achieved through good communication between neighboring landholders
and through local forms of governance.
Dr. Daniel Nepstad is a tropical forest ecologist specializing in the
effects of drought on Amazon forests, and in forest recovery following land
abandonment . He has been a scientist at the Woods Hole Research Center
since 1990. In 1995, he co-founded the Amazon Institute of Environmental
Studies (Instituto de Pesquisas Ambientais da Amazonia) based in Belem,
Brazil, which is now the largest non-governmental research institution in
Amazonia. Dr. Nepstad has also been conducting field research in Amazonia
since 1984, and during that time, has documented the precarious water
balance of vast areas of Amazonian forest. His current research efforts are
focused on the prediction of fire risk in Amazonia, including the rainfall
regime at which Amazon forests become vulnerable to fire, and the land-use
patterns that are most likely to ignite fire-prone forests.
Dr. Nepstad and his colleagues are also engaged in identifying possible
solutions to the problem of Amazon burning, through research with farm
communities and ranchers, and through dialogue with government
policy-makers in Brazil. In recognition and support of this application of
science to public affairs in Brazil, Dr. Nepstad was awarded a Pew
Fellowship in Conservation and the Environment in 1994. Dr. Nepstad has a
Ph.D. degree from Yale University, CT, an M.S. degree from Michigan State
University, MI, and a B.A. degree from Kalamazoo College, MI.
Dr. Compton Tucker first came to the NASA/Goddard Space Flight Center in
1975 as a National Academy of Sciences post-doctoral fellow, and later
joined NASA as a scientist in 1977. From 1975-1980 he concentrated on data
collection and analyses using spectrometer data and hand-held radiometers.
Since 1980, Dr. Tucker has used NOAA and Landsat satellite data for
studying vegetation dynamics including deforestation, desert boundary
determination, and terrestrial primary production He is presently working
on describing African and Asian arid and semi-arid vegetation dynamics
using daily satellite data from 1981-1998; continuing work on deforestation
and habitat fragmentation in the Amazon; studying the relationship between
precipitation and grassland production in the Sahelian Zone of Africa; and
studying higher northern latitude photosynthetic increases from 1981-1998.
Dr. Tucker received his B.S. degree in biological science in 1969 from
Colorado State University in Ft. Collins, CO. He later received an M.S.
Degree (1973) and a Ph.D. degree (1975) from the Colorado State
University's College of Forestry.
The Next Seminar is scheduled for Monday, April 20, 1998
Tentative Topic: Recent Developments in Modeling the Impacts of
Aerosols on Climate
For more information please contact:
Anthony D. Socci, Ph.D., U.S. Global Change Research Program Office, 400
Virginia Ave. SW, Suite 750, Washington, DC 20024; Telephone: (202)
314-2235; Fax: (202) 488-8681 E-Mail: TSOCCI at USGCRP.GOV.
Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. A complete archive of seminar summaries is also
maintained at this site. Normally these seminars are held on the second
Monday of each month.
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