In some ecosystems it maintains the dynamic equilibrium responsible for high biodiversity and economic productivity. In others, such as lowland and mountain rain forests, it destroys the forest cover and leads to long-term site degradation. But, in most areas of the world, wildfires burning under extreme weather conditions have severely damaged economies and human health and safety and caused major disasters. Indeed between 1950 and 1990 a total of 4,137 people were killed in forest fires in China. The last major fires in central Eurasia were in Mongolia, where 10.7 million hectares of forest and steppe vegetation were burned in 1996, followed by a further 12.4 million hectares in 1997.
Health hazards Smoke pollution from burning vegetation sometimes causes death and illness.
The most serious pollution problems in the 1980s and 1990s have been in the Amazon Basin and in Southeast Asia. A study on asthma attacks in children showed that high concentrations of carbon monoxide, nitrogen dioxide and inhalable suspended particulate matter, all generated by the fires, were to blame - the smog of September 1997 caused the worst smoke pollution ever recorded in the region. Wildfires in vegetation contaminated with radioactivity cause uncontrollable releases of such radionuclides as caesium 137C, strontium 90 and plutonium 239. This happened, for instance, in the severely contaminated region near the Chernobyl nuclear power plant. Recent estimates suggest that some 2 to 5 billion tonnes of carbon stored in vegetation may be released annually by fires and other burning of plant biomass including biofuels.