Changes in climate have the potential to significantly affect fire regimes, especially in areas where climate, and not fuel, tends to be the limiting factor. Conversely, fire—by emitting greenhouse gases and aerosols—is also thought to contribute to overall global warming.
A number of studies have been conducted on the likely effects of climate change on present-day fire regimes. In temperate regions, including the western United States, Australia and the boreal forests of Canada and Russia, researchers are predicting that increased temperature will extend typical fire seasons, with more fires occurring earlier and later in a given year. Although the effects will likely vary considerably among different ecosystem types, the total area burned will increase in some regions, as will fire severity and related economic losses. Fire suppression efforts will not keep pace with these changes, and many fires may effectively burn through remote landscapes unimpeded by control efforts. Increased fire frequency and severity could also increase the risk that some rare species and ecosystem types will be lost.
Tropical forests globally have warmed by half a degree in the last 20 years, and this is expected to increase by a further 3 to 8 degrees by the end of the century. In tropical rainforests, specifically, global warming could exacerbate existing problems stemming from forest fragmentation, agricultural burning and other human uses if it promotes drier climates or stronger El Niño-Southern Oscillation droughts.
How do prescribed burns and other treatments such as forest thinning affect carbon storage? In 2010 the Ecological Society of America synthesized the science on forests and carbon for the United States, including the issue of how fuels management affects carbon stocks. In general, there is much we still don’t know about carbon budgets in different ecosystem types, especially those that naturally experience periodic fire. It is known, however, that the periodic controlled burns used to manage many natural areas, such as longleaf pine ecosystems, do not release a great deal of carbon relative to what is stored in the forest stand.
Increasingly, managers are explicitly striving to increase the resilience of ecosystems to the effects of climate change and other disturbances. (Resilience = the capacity of a system to absorb disturbance, undergo change and still retain essentially the same function, structure, identity and feedbacks.)
