Impacts of Fire on the Global Environment

Wildland fire and other sources of biomass burning generate carbon emissions every year that are in the vicinity of 20 to 50% of annual global carbon dioxide emissions from fossil fuel combustion and cement production. Changes in the net emissions from biomass burning have the potential to significantly impact atmospheric composition, terrestrial carbon storage, and the forcings associated with changing climate. Determining the feedbacks between fire and changing climate is complex, as multiple processes and their interactions with ecosystem dynamics, climate, and fire regimes need to be considered, quantified and integrated. Understanding of and ability to quantify and model many of these processes is improving rapidly, but is still inadequate for assessing the interactions between fire processes, the atmosphere, and climate. Some of the most basic questions center on the effects of changing fire regimes on carbon balance. This requires quantifying emissions from wildfire and other types of biomass burning—and balancing these with information on uptake of carbon by regrowing vegetation, the impacts of biomass fuel use on fossil fuel emissions, and the effects of management practices on fire-related carbon emissions.  Postfire decomposition of dead biomass continues to produce carbon dioxide for many years after severe fires. The wide variations in emissions related to fuel moisture and burning conditions are typically poorly quantified, and often not considered in development of regional or global emission estimates. It is also critical to recognize that the impacts of fire on the atmosphere are not restricted to carbon dioxide emissions.  Smoke from biomass burning includes many compounds, such as methane, aerosols, and soot particles that have varied effects on atmospheric forcing potentials for climate change. Changes in soil microbiologic activity after fire can alter soil emissions of carbon dioxide and methane for several years.  Changes in vegetation structure and snow cover related to fire or climate change can affect surface reflectance (albedo) over broad areas. There is a great deal of active research in many of these areas.  As both data and models continue to improve, we will be able to better understand,  quantify, and project crucial feedbacks between fire regimes  and climate, and to determine more accurately how various management practices can affect the interactions among fire, ecosystem structure and process, carbon storage, the atmosphere, and climate.