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Fires in the Amazon:
an analysis of NOAA-12 satellite data, 1996 - 1997.
December 1, 1997
The number of fires in the Brazilian Amazon between July and
November increased over 50% between 1996 and 1997. The NOAA-12
satellite recorded 29,571 fires in the Amazon region on 136 days
between July 1, 1996 and November 30, 1996 and 44,734 fires on
118 days between July 1, 1997 and November 22, 1997, an increase
of over 50% from 1996 to 1997, even though data are available for
fewer days in 1997 than in 1996. The average number of fires per
day increased 75%, from 217 in 1996, to 379 in 1997. A previous
analysis, based on a more limited sample earlier in the year, had
shown a smaller increase. 1/
The data are generated by the Advanced Very High Resolution
Radiometer (AVHRR) on the NOAA-12 weather satellite, which
detects thermal anomalies, and passes over the Amazon daily.
Fires are mapped and counted by the National Institute for Space
Research (INPE) in Brazil (http://condor.dsa.inpe.br/mapas_que).
The largest differences between the two years occurred in
November and October, and result from increased economic
activity, particularly burning of cattle pasture. The difference
also reflects the extended dry season of 1997 caused by El Ni?o.
Normally seasonal rains start in late September or early October
in most of the Amazon, curtailing fires. 5/ In 1997, airports were
still closing because of thick haze in November. The satellite
recorded 2,638 fires in 22 days in November 1997, as opposed to
1,542 in 27 days in November 1996, an increase of 71%, over
fewer days. In October 1997, 10,305 fires appear in 28 days, over
three times more than the 3,119 counted for 26 days in October
The actual number of fires in the Amazon in both years is
considerably higher than the totals obtained by the NOAA-12
satellite, for two reasons. The NOAA satellites, because of their
trajectories and the locations of current receiving stations,
cover the northern and western Amazon poorly. In addition, the
NOAA-12 satellite passes over the region at night, when the
number of fires is lower than during the day. INPE stopped
analyzing NOAA-14 images, taken during the day, for the burning
season of 1996, arguing that solar reflection on hot days could
be confused with fires by the satellite?s sensors and inflate the
number of fires. While the NOAA-12 images thus under-count
fires, comparison of data sets from different years does show
changes in the level of burning.
New research from the region strongly suggests that fires
themselves are rapidly becoming at least as great a threat to the
biological integrity of the Amazon as is deforestation, as well
as increasing Brazil?s contribution to global CO2 and other
greenhouse gas emissions. Fires are set in the Amazon to burn off
cleared primary forest, and also to burn old cattle pastures and
secondary forest areas. Deforestation per se accounts for only a
relatively small part of the fires every year. Some 70% of the
fires burn on land already deforested. 2/
The Woods Hole Research Center and the Institute for Amazonian
Environmental Research (IPAM) have shown that selective logging
and ground fires ? fires that burn largely undetected by the
satellites, beneath the forest canopy ? are degrading an area
approximately equal to the area deforested annually in recent
years. Selective logging, as studies by the Institute for Man and
Nature in the Amazon (IMAZON) show, contributes to the
flammability of the forest through opening up the canopy and
leaving combustible material behind. 3/ Ground fires, often in
previously logged areas or areas bordering already deforested
lands, in conjunction with dry weather, are making the forest
dryer. The increased burning this year means that ground fires,
which may cover hundreds or even thousands of square kilometers,
also increased, even though they do not appear in the satellite
images. Deforestation, according to INPE?s last figures (for
1994), was about 15,000 square kilometers a year. This means that
a similar area, unrecorded by satellite images, is being
degraded through selective logging and ground fires annually.
The Woods Hole, IMAZON and other new findings indicate that CO2
emissions and other global climatic effects of Amazon fires have
heretofore been underestimated, by as much as 30%. Recent long-
term research on forest fragments in the Amazon shows that up to
36% of biomass is lost in fragments within 100 meters of edges
in the first 10 - 17 years after fragmentation. The authors
conclude that decline in biomass in forest fragments could be a
significant, and uncounted, source of greenhouse gases such as
The Woods Hole Research Center/IPAM research on fires has
identified an alarming new trend. Much of the forest of the
eastern and southern Amazon, which depends on deep-soil water
reserves to stay green in the dry season, is becoming flammable
because of logging and drought. Hitherto, virgin forest has
prevented the spread of fires because it was too moist to burn.
Should large parts of the intact forest dry out enough to burn,
as appears to be occurring, much quicker and larger scale
destruction of the forest becomes possible, in a vicious circle
of drying?larger fires?more drying. The Woods Hole group set an
experimental fire in intact closed forest in Par? state for the
first time this year. These results show that the rate of
deforestation of formerly intact primary forest, as measured by
analysis of Landsat images ? formerly considered the central
indicator of forest destruction -- is no longer the only
significant, or even the most urgent, threat to the forest.
Should intact closed forest begin to burn, a previously
incremental process (the loss of 0.4%, or 0.5% of the forested
area of the Amazon to deforestation yearly, as was the case in
the 1980s and 1990s) could become a catastrophic positive
feedback loop. Climate models predict a slightly drier climate in
tropical areas under global warming.
While increased burning involves hundreds of thousands of actors
spread across a continental region, much can be done to address
the problem. One half of the area burned in 1994 and 1995
resulted from accidental fires . These fires have substantial
costs for small and large farmers alike and benefit no one.
Efforts to assist rural Amazonians to prevent accidental fires
(through fire breaks or enforcing compensation for fires that
damage others? property), and to rely less on the use of fire for
agriculture (through mechanization) would make a difference. In
addition, passage of the Environmental Crimes Act, currently
stalled in the Brazilian House of Representatives, would give
the Brazilian environmental agency, IBAMA, statutory authority to
enforce the law, including restrictions on burning and
deforestation, for the first time since 1989.
Whether or not deforestation rates have increased in the Amazon
will only be known with the release of INPE?s analysis of
Landsat images. INPE has promised to release data for 1995 and
1996 by end of the year. Increased burning, and new research
results on the effects of fire, however, unequivocally
demonstrate that the rate of deforestation is no longer the only
important indicator of threat to the biological integrity of the
Amazon forest. Under current conditions of drought stress, fire
itself may rapidly become the vector of greater and much quicker
destruction than previously imagined possible, with potentially
enormous global repercussions.
1. Fires in the Amazon - an analysis of NOAA 12 satellite data 1996
-1997. Environmental Defense Fund, September 23, 1997.
2. Fires in the Brazilian Amazon: The Story from the Ground.
November 1997. Woods Hole Research Center.
3 Fire as a recurrent event in tropical forests of the eastern Amazon.
Mark Cochrane and M. Schulze, in press.
4. Biomass collapse in Amazonian forest fragments. W.F. Laurance et al,
Science, Vol. 278, 7 November 1997 pp 1117-1118.
5. Fires in Brazilian Amazonia: The story from the ground. Ibid.
Summary of Analysis for 1996
Actual Fires Counted 29571
Number of Days in Period 153
Data Days Available 136
Average No. Counted per day 217
Summary of Analysis for 1997
Actual Fires Counted 44734
Number of Days in Period 153
Data Days Available 118
Average No. Counted per day 379
Note: Daily fire totals broken down by state are available on
request for July-November for 1996 and 1997.