- 1 - The Second Congress of Students of Environment Protection of South Eastern Europe Kopaonik Mountain, 13-15 May, 2009. THE INFLUENCE OF WILDLAND FIRES ON AIR QUALITY Dejan Ristić, Lidija Milošević, Danijela Avramović, Milan Savić Faculty of Occupational Safety, University of Niš, Niš, Serbia INTRODUCTION Every year tens of millions of hectares of forests, woodlands, and grasslands burn globally. Some are burned intentionally for land conversion, pasture renewal or hazard reduction, or wildlife habitat improvement, but most are burned by uncontrolled wildfire. Smoke emissions from wildland fire can be harmful to human health and welfare, impair visibility, and contribute to greenhouse gas emissions. Wildland fires are major sources of trace gases and aerosol, and these emissions are believed to significantly influence the chemical composition of the atmosphere and the earth's climate system. The wide variety of pollutants released by wildland fire include greenhouse gases, photochemically reactive compounds, and fine and coarse particulate matter. Through direct emissions and secondary chemical and physical processes, wildland fire can have a significant impact on tropospheric chemistry and serve as a major source of air pollution. Global wildfire emissions vary substantially from year to year. Nonetheless, average annual carbon emissions from wildfire are 20–40% of those from fossil fuel combustion and cement production. Results of field studies and modelling efforts indicate that changing climate is likely to increase the extent and frequency of wildfires, highlighting the importance of accurately quantifying the regional and global effects of wildfire on carbon stocks and on atmospheric carbon compounds. The nature and strength of feedbacks between fire and climate will depend not only on changes in the area that is burned annually, but perhaps more importantly, on how those fires burn and how ecosystems respond and recover. Changes in burn severity can result in large differences in the amount of fuel consumed, emissions to the atmosphere, and the capacity of ecosystems to recover carbon after a fire. Even low-severity surface fire may cause significant changes in soil respiration, and these changes may either increase or decrease the net effects of fire on atmospheric carbon. Postfire recovery to a different vegetation type—which may occur in response to changing climate, unusually high burn severities, or other factors—also has the potential to affect the amount and rate of carbon storage on the landscape. Past and future vegetation and fire management activities also play a role in ecosystem condition and carbon storage, although the nature and magnitude of these impacts vary greatly among regions and ecosystems. Improved understanding of the extent and severity of fire, the feedbacks between fire and climate, and the effects of changing fire regimes on all aspects of the carbon cycle is needed before we can fully predict the magnitude, or perhaps even the direction, of the effect of changing fire regimes on global carbon balance and atmospheric chemistry. In 2002, a major drought and prolonged high temperatures occurred in central Russia that resulted in unprecedented wildland fires. These fires occurred under extreme fire danger conditions and were impossible for the Russian authorities to extinguish. It is perhaps somewhat unique that the fires were first burning peat bogs and later forests, causing very massive smoke. Smoke was transported into Moscow itself for a period of almost 2 months, sometimes reducing visibility to below 60 m. These fires resulted in perhaps the most significant exposures of fire smoke to a major population center in recorded history. These changes may be explained as resulting from a combination of extreme weather, elevated surface ozone, and to a lesser extent changes in solar radiation. GREENHOUSE GAS EMISSIONS FROM FIRES Globally, fires are a significant contributor of carbon dioxide and other greenhouse gases in the atmosphere. Fires account for approximately one-fifth of the total global emissions of carbon dioxide (Levine and Cofer 2000; Schimel 1995). Andreae and Merlet (2001) calculate that 5,130 Tg per year of biomass is consumed in fires, emitting 8,200 Tg per year of carbon dioxide, 413 Tg per year of carbon monoxide, and 19.4 Tg per year of methane. The accuracy of these global estimates is thought to be within plus or minus 50 percent, with the bulk of the error resulting from inaccuracies in the estimates of the area burned and the mass of fuel consumed. Fires in temperate ecosystems are minor contributors compared to the world’s savannas, boreal forests, and tropical forests. More than 60 percent of the totals listed in the previous paragraph are released from savannas and grasslands, and another 25 percent from tropical forests. Burning in tropical Africa is dominated by savanna fires; in tropical Asia, by forest fires; and in