In the USA during 1966, 65% of the 110,000 wildfires occurring in the USA were started accidentally by man, 26% were of incendiary origin, and 9% were started by lightning. These percentages vary widely by region, however. (In the 12 Rocky Mountain states, for example, 52% were started by lightning and 2% were incendiary; in the 13 Southern states, 1% were started by lightning and 38% were of incendiary origin.).
During the 1980s and 1990s, in the USA the number of fires and the area burned have both been reduced with the development of more efficient fire prevention and control technology. The USA Forest Service has developed a fire danger index which combines all the major determinants (including moisture content and arrangement of the trees and other vegetation, atmospheric temperature, humidity, wind and topography) of fire susceptibility, and this provides a measure of the potential fire danger in a given area at a particular time. Nevertheless, a fire still requires an igniting agent which may be human-caused, such as a match or cigarette, or natural, such as lightning.
In 1998 the Group of Seven with agreement from Russia will provide satellite observation data to countries fighting forest fires.
In Brazil, deforestation has done nothing but go up. Where the most money has gone is where the fires have increased the most in the 1990s. For example, half of the fires recorded in 1997 were in Mato Grosso, where the World Bank lent US$205 million to save the rain forest in a natural resource management programme.