May 15, 2012

Wildfire: More Complicated than You Might Think

 Photo Credit: Dr. Llyod Glenn Ingles, California Academy of Science

After many years as a software engineer, I dedicated the last few years to pursuing a graduate degree in Biology. My research concentrated on wildfire ecology and modeling, so I was particularly interested in a recent news story about how the black-backed woodpecker is in serious decline over much of its native habitat. This decline is due in large part to successful wildfire suppression efforts in western United States forests. After studying both the history and the current science-based understanding of wildfire, I find the black-backed woodpecker’s situation emblematic of how traditional attitudes towards wildfire have affected the current health of many ecosystems.

Around the turn of the 20th century, the ideas of ecological succession and climax communities were introduced. Succession is the development of an ecological community over time.  A climax community is the final stage of succession, a steady-state community that develops if an ecosystem is not disturbed by events such as fires, floods, or logging. While these concepts are still important in ecological science, some conclusions based on them are not. For example, many believe that the climax community is the “ideal” natural state of an ecosystem. In the climax-community-as-ideal view, disturbances, most notably fire, are considered harmful. Wildfire prevention campaigns have reinforced the idea that wildfire is destructive to the natural order. Nearly everyone is familiar with Smoky Bear and his entourage of cute forest critters reminding us that only we can prevent wildfire.

A wildfire caused by a lightening stike burns in the Cascade Mountains west of Sister's Oregon.

Armed with growing technology and resources during the 20th century, we humans were able to take action against “harmful” wildfire on a large scale. Efforts to prevent and extinguish wildfires met with great success over the second half of the 20th century. The thinking was that these efforts allowed ecological communities to reach their “ideal” climax state, protected valuable resources, and kept forest denizens safe.

One consequence of fire exclusion policies has been that more people started building homes in wildlands with the expectation that their homes would be safe. If a fire started, it would quickly be put out. Protecting human-made structures has become a major goal of fire suppression efforts.

Many wildland management policies have been based on the false assumption that fire is only a harmful force in an ecosystem. Ecologists now understand that fire plays a vital role in ecosystems and that every ecosystem is adapted to its fire regime (the frequency, timing, and intensity of wildfire). In some ecosystems, small frequent fires clear out living and dead vegetable matter (also known as fuels) in the forest understory without harming mature trees. In others, occasional intense fires kill some or all of the standing trees which then provide habitat for certain species. Many species are actually fire-dependent; without occasional fires they can be driven to extinction. The seeds of some plants require a fire’s heat before they can sprout. The species that inspired this blog, the black-backed woodpecker depends on burnt trees for one of its major food sources, beetle larvae.

The good news is that with the current, better understanding of how wildfire relates to different ecosystems, wildland managers in many areas are treating fire as a natural process. Some natural fires are being left to burn as long as they don’t threaten human infrastructure, and planned burns are often conducted in a way that attempts to mimic an ecosystem’s natural fire regime. However, many challenges remain. In wildlands where fire has been suppressed for decades, not only has the lack of fire stressed fire-dependent and fire-adapted species, but also the buildup of unburned vegetation will result in abnormally severe fires and increased mortality when they do burn. In addition, economic interests and traditional views often conflict with science-based best practices for wildlife management.

In my nascent career as an ecologist, my job is to present an objective, science-based view of the effects of fire and its suppression on an ecosystem. But as someone who is fascinated by the natural world, I can’t help but hope that fire is allowed to play its necessary role in keeping ecosystems diverse and healthy. After all, black-backed woodpecker depends on it.

About the author:
Tim Sheehan, Ph.D.
Ecological Modeler, Team Lead- Decision Support & GIS
Tim is an Ecological Modeler at CBI working on a wide range of computational models to analyze alternative futures for ecosystems. In addition to his recently completed master's degree in Biology from the University of Oregon, he also has master's degrees in Geology and Computer Science.
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