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Title:    Fires in the Amazon: An Analysis of NOAA-12 Satellite Data
Source:   Environmental Defense Fund 
Status:   Distribute freely with accreditation
Date:     December 1, 1997

  ENVIRONMENTAL DEFENSE FUND
  1875 Connecticut Ave., NW,10th Fl.
  Washington, D.C. 20009

  Telephone:  (202) 387-3500
  Facsimile:  (202) 234-6049; steves@edf.org

  Fires in the Amazon:
  an analysis of NOAA-12 satellite data, 1996-1997.

  Stephan Schwartzman
  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 Nino.  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 1996.

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 CO2.4

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 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 acres 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.

 

Notes:

  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.  Biotropic.
  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

  July                   1740
  Aug                    10293
  Sep                    12877
  Oct                    3119
  Nov                    1542

  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

  July                    2453
  Aug                    14986
  Sep                    14352
  Oct                    10305
  Nov                     2638

  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.

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