CANOPY MAGAZINE FALL 2012
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Landsat Photo: Wallow Fire, Arizona
water stress, which has been occurring in the Amazon over the last decade. Drought and higher temperatures can also create conditions for insect infestations that subsequently kill trees, as the bark beetle has been doing for the past decade throughout vast areas of evergreen forests in the western US and Canada. However, it is the synergy between drought and fire that is most destructive. Fire intensity and frequency increase significantly in years of severe drought. Fires occurring in drought years are capable of greater forest destruction because drought conditions create much warmer temperatures at the forest floor, thereby drying the dead wood and leaves that fuel the fires. In the Amazon, drought and heat waves also create much warmer nighttime temperatures, which reduces the amount of dew and allows fires to burn through the night. In drought years, individual fires can damage millions of acres of forest and leave giant scars visible from space. In the coterminous US, 7.7 million acres - the most ever recorded - burned during the severe drought of 2012. A major concern for the coming decades is that humans are creating conditions that will greatly increase the frequency of strong fires and widespread tree mortality. This is true throughout the Americas – from the tropical Amazon, to temperate forests in the western US, to the boreal evergreen woodlands in Alaska and Canada. Continuing human-induced deforestation and
fragmentation create forest “edges,” which are hotter and dryer and therefore more susceptible to fire. Human-induced climate change is almost certainly increasing the frequency of moderate to severe drought and, as a result, increasing the occurrence of intense fires. Furthermore, the destruction of forests releases carbon dioxide, a heat-trapping gas, and contributes to rising average global temperatures and more extreme droughts. Thus a feedback occurs, leading to fires that are increasingly greater in scope and frequency. Forest ecosystem destruction through degradation, fire, and drought is increasing markedly as a result of human decisions and actions. Without strong efforts to curb deforestation and climate change in the near future, a threshold could be reached such that the composition of vast portions of the tropical, temperate, and boreal forests of the Americas will be transformed. Our science is advancing the understanding of drought-fire synergies so that effective solutions to the challenge of conserving forests can be identified.
In the coterminous US, 7.7 million acres - the most ever recorded - burned during the severe drought of 2012.