Twelve months (April 1992 – March 1993) of the Global Fire Product (GFP) have been studied in detail and the spatial and temporal distribution of fires has been reported (see key publications below). A total of 6.5 million fire pixels were detected in the 12 months of 1 km resolution AVHRR data analysed. However, these are not evenly distributed throughout the year. There is a peak in global fire activity in July and August. It then decreases slowly reaching a minimum in early November when the number detected is only 28% of those detected during the period of peak burning. From November fire activity increases again reaching another lower peak in late December and January after which activity reduces
The total number of fire pixels detected in each 0.5 deg by 0.5 deg grid cell during two periods is shown below. While over 70% of fire pixels are located within the tropics, 50% of all fire pixels detected were on the African continent. Most of the fires are set in the savanna regions. The reasons for burning are numerous and vary across the continent, but some of the more common ones are: burning to remove unpalatable stubble and to initiate off-season re-growth of fresh shoots, clearing ground for crops, establishment of fire-breaks around settlements, removal of parasites, to drive game out of hiding and to make pathways accessible. Other regions where very high concentrations of fire activity were seen are in mainland Southeast Asia, the Orissa province in Eastern India, parts of the Cerrado in Brazil and Arnhem land in the Northern Territories of Australia. Although the number of fires occurring in temperate and boreal biomes is much smaller than in the tropics, they can have a big impact on land cover and the global carbon cycle. Fires in boreal biomes can be of extremely large extent, consume very high fuel quantities and are often left to burn out naturally.
Use of the data
Products of different grid sizes and over different time durations can easily be constructed from the basic product. Typical information that can be provided by the GFP is :
- Spatial localisation of fire events
- Spatial variation in the number of fire events
- Seasonality of fire.
With respect to the last point, although the day on which each fire event was detected is recorded, the seasonality, i.e. the time period and duration of the burning season may be of interest. The figures below show examples of such derived products:
- Season Start: This was defined as the time when 10% of all fire pixels in the year were detected. This threshold was chosen in order to reduce the effect of occasional or very low levels of fire activity which may take place throughout the year;
- Seadon End: This was defined as the time when 90% of all fire pixels were detected. Again this threshold was imposed in order to filter out very low levels of fire activity;
- Mid Season: This was defined as the time when 50% of all fire pixels were detected. This is not the same as the time of peak fire occurrence, which can be at any time within the fire season;
It is not advised to use the GFP to estimate area burned as the product indicates only the presence or absence of fire in a pixel. Nor can it be used to count the absolute number of fire events in a given location as it is only a temporal sample. Although a research study using 1 km AVHRR data combined with high resolution LANDSAT data in Southern Africa has shown that it is feasible to estimate burned area from the 1 km data, its results cannot be universally applied. Extensive research for different vegetation types would need to be carried out if such a scheme were to be adopted. Current research is focused on retrieving burned area directly from low resolution satellite data.
For more information on this topic, please contact Jean-Marie Grégoire
A global analysis of vegetation fires using satellite images: spatial and temporal dynamics, Dwyer, E., Grégoire, J.-M. & Malingreau, J.P.,1998. AMBIO. 27, 3, 175-181.
Characterization of the spatio-temporal patterns of global fire activity using satellite imagery for the period April 1992 to March 1993, Dwyer, E., J. M.C. Pereira, J-M. Grégoire, and C. C. DaCamara, 1999. Journal of Biogeography, 27(1), 57 – 69.
Global spatial and temporal distribution of vegetation fire as determined from satellite observations, Dwyer, E., Pinnock, S., Grégoire, J.-M. & Pereira, J.M.C., 2000. International Journal of Remote Sensing. Vol. 21, No. 6/7, 1289-1302.
Climate and vegetation as driving factors in global fire activity, in Biomass Burning and its inter-relationships with the climate system, Dwyer, E., J-M. Grégoire, and J.M.C. Pereira, 2000. J.L. Innes, M. Beniston and M.M. Verstraete (editors), Advances in Global Change Research, Volume 3, Kluwer Academic Publishers, Dordrecht / Boston / London, 2000, 171-191