Understanding Change in the Biosphere
Released August 1998.
While the 1997-98 El Nino was soaking California, severe drought has reduced rainfall in the tropical forests of Brazil by such a significant amount that the hazards of devastating fires could threaten an area estimated to equal the size of California over the next several months.
With attention in Brazil turning to these alarming fire dangers, NASA Ames researchers have collaborated with scientists at the Woods Hole Research Center and the Brazilian Space Agency (INPE) to produce a new map of pending fire risk for the entire Brazilian Amazon region. The mapping application shows that approximately 400,000 square kilometers of intact forest may become highly susceptible to fire during the 1998 burning season (June to November).
This fire risk map, produced as part of the joint "RisQue98" project, was presented in a public hearing in the Chamber of the Brazilian House of Deputies this spring and was also published in Brazilian national newspapers. The purpose of the map is to provide an advanced warning so that farmers, ranchers, loggers, and government agencies can implement measures to reduce the spread of accidental fire where the risk is particularly high.
The drought has caused a rise in the normal fire risk of the area in multiple ways. A normal rainy season "greens up" the rainforest to the point that it remains somewhat damp and fire-resistant throughout the dry season. The lack of rain this past season is evident in the low moisture level of the soils, as well as drier trees which form the rain forest canopy. These trees will drop a higher percentage of their leaves because of this dryness, therefore letting more sunlight into the floor of the rain forest, compounding the dryness and flammability issues.
Brazil's weather service provided the NASA-ARC/Woods Hole Research Center with the temperature and rainfall statistics since early 1997. The team built a composite Fire Risk Map based on this input, along with computer model predictions of moisture content of the soil, evapotranspiration, logging zone areas, fire prevention zones, land use and forest zones.
The latest climate predictions in Brazil are for continued severe drought. Large areas of forest on parched soils, which haven't been recharged with new rainwater, are becoming vulnerable to the incursion of accidental fires. The possibility for an ecological and social catastrophe is real and immediate over vast areas. Early awareness can lead to measures to protect or at least minimize the impacts of natural disasters.
FIGURE RisQue98
More more detailed information see http://www.whrc.org/tropfor/fire/risque98introen.htm
A Dynamic Global Vegetation Model (DGVM) has been developed as a new feature of the NASA-CASA (Carnegie Ames Stanford Approach) ecosystem production and trace gas model (Potter and Klooster. 1997). This DGVM includes seasonal phenology algorithms calibrated using global interannual data sets from the Advanced Very High Resolution (AVHRR) satellite "greenness" index (Potter and Brooks. 1998). The coupled CASA-DGVM design is based on a resource-ratio hypothesis of vegetation change, namely (1) plant competition for resources (water and light) over relatively short time periods of months and seasons, and (2) the long-term pattern in the supply of growth-limiting resources such as water and nutrients, i.e., the resource-supply trajectory. The model generates global gridded estimates of primary production, above and below ground biomass, leaf area index (LAI), and trace gas fluxes.
Global distribution of vegetation types predicted from the CASA-DGVM using mean (1931-60) climate conditions.
FIGURE Predicted Vegetation
More more information see Dynamic Global Vegetation Modeling
Last Updated: Jun 5, 2003
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