Comparing the decades of the 1980s and 1990s. Comprehensive national, regional or global statistics on wildland fires are not available that would allow a reliable and precise comparison of the global fire occurrence in the 1980s and 1990s. However, some general observations can be made. Both decades experienced high inter-annual regional and national variability of fire occurrence and fire impacts. El Niņo episodes such as in 1982-1983 and 1997-1998 were the most important climatic oscillations affecting area burned and fire impacts in both decades. In these years, most of tropical Asia, Africa, the Americas and Oceania regions experienced extremely extended wildfire situations. During 1997-1998, the amount of land-clearing fires and other escaped fire situations have increased in the equatorial forest regions of Southeast Asia and South America.
The northern temperate/boreal forest zone also experienced extremely dry years in both decades. Central-Eastern Asia was affected most severely in 1987, particularly Central-Eastern Siberia and the northeast of China. The Far East of Russia also was severely affected by wildfires during the 1998 drought.
Statistical evidence from Canada suggests that there is a trend of increasing area burned starting in the early eighties and continuing to increase in the 1990s. Wildland fire statistics for National Forests in the western United States also show an increase in area burned from the mid-1980s onward compared to the earlier part of the 20th Century (Figure 1-1). Differing fire response strategies in Canada today and unnatural fuel accumulations in the U.S. because of fire exclusion help to explain some of these increases in area burned.
It is not surprising in the aftermath of the extensive 1910 wildfires in the western United States that public policies were developed that emphasized fire suppression programmes over prescribed fire programmes. This programme emphasis on fire suppression was universally accepted by society and politicians. But since 1910, a large body of scientific knowledge has developed regarding fire history, fire regimes, and fire effects; the decline in the health of ecosystems has reached alarming proportions; and large, high intensity wildfires are increasing in size during the past two decades (Figure 1-1). Here is an example where the accurate recording of area burned on an annual basis has produced a wildfire database that is now highlighting an alarming trend in larger fires towards the end of the 20th Century.
Figure 1-1 Total wildfire hectares burned in the 11 western states on all Federal lands between 1916 and 1996.
Summarizing the wildfire trends of the 1980s and 1990s, it can be concluded that there is no unidirectional tendency. Some areas suffered more fires due to increasing land-use intensity. Other forest regions have become more susceptible to larger and more damaging fires as a result of long-term fire exclusion. An important consideration is the fact that large areas of degraded forests and other wooded lands have been converted to grasslands and shrublands with repeated fires. These grasslands and shrublands are prone to burn much more frequently, inhibiting the succession back to tree cover.
