Forest fires in Indonesia
Because of the ongoing destruction and degradation of rainforests, the formerly rare phenomenon of forest fires became an important ecological agent in areas of tropical humid climate and its consequences are of global impact. Contrary to boreal or Mediterranean forests, evergreen tropical rainforest vegetation is not well adapted to fire, and repeated fire events lead to rapid and irreversible degradation already after few fire events. This has been shown to be especially true for East Kalimantan’s rainforest. Hence, it is of utmost importance to prevent or control destructive forest fires in order to avoid or reduce damage.
Therefore, it is crucial to identify regions with elevated fire danger induced through natural geographic conditions or human intervention. Although this problem is of global significance, there are still few experiences with fire danger estimations for tropical rainforest areas.
The dynamic fire-danger map
Objective of the project was therefore the development of a simple empirical model for fire danger based on existing data, e.g. land-use, fuel load, terrain and meteorological conditions. The map should be dynamic and reflect medium to short-term changes due to changed meteorological and vegetation conditions in order to give a realistic estimate of fire danger at a given place for a given time period. Satellite images from the NOAA AVHRR (Advanced Very High Resolution Radiometer) were used to characterize vegetation condition. A comperative index was calculated comparing the NDVI (Normalized Difference of Vegetation Index) of a given time period to its highest value. Thus, the deviation from the optimum condition can be used to characterize the status of vegetation as an input to the model.
Other input data were a drought index based on meteorological observations, a land cover map to describe fuel load and type, an accessibility map and a coarse resolution digital elevation model. All data were assigned weights derived from historical fire occurrance data and the resulting fire danger for any location was calculated according to the weights of the combination of factors (e.g. a combination of low NDV, low elevation, Grassland vegetation and vicinity to roads results in a high fire danger rating).
ArcView GIS Extension
In order to acquire a dynamic, updateable data product, a software was developed based on the algorithms found through the analysis of historical fire data. This software enables the generation of an up-to-date fire danger map with frequently changing data. The fire danger map is output at a scale of approximately 1:500,000 and in ArcInfo Grid format. A wizard based software tool enables the user in ArcView GIS 3.2 with the Spatial Analyst Extension to produce a fire-danger map with changed data or assumptions.