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Expert Voices

With Warming, Wildfires Growing More Difficult to Predict (Op-Ed)

Night View of The Rim Fire
This photograph shows the Rim Fire burning in California at night on August 21, 2013. (Image credit: InciWeb)

Peter Fulé  is a professor in the school of Forestry at Northern Arizona University (NAU). He contributed this article to LiveScience's Expert Voices: Op-Ed & Insights.

Disastrous wildfires occur so often that people who don't live in one of the states on fire at the moment can be forgiven for skipping to other news. The exception is when tragedies — such as the deaths of 19 firefighters from Prescott, Ariz. — send a shiver across the nation.

With the prospect of warmer and drier years ahead, climate changes align statistically with a greater probability of even more, even larger and even more environmentally severe wildfires. But climate change affects more than just the weather conditions under which a fire burns. Climate affects everything in the environment, meaning that future fires will be different in ways that no one can clearly foresee.

Living and dead vegetation make up the fuel that burns in a wildland fire. Warmer and drier conditions make present-day fuels, such as forests, more likely to burn, but changing climate will also affect future fuels. In much of the West, drier conditions equal less growth, so the total amount of fuel should decline. In some places where cold temperatures currently preclude trees, though, the opposite can occur: warming may help form more fuel.

Also, the total amount of vegetation isn't the only important factor, because many species will shift ranges. Forests that used to be characterized by mixes of species, like pines and oaks or spruce and fir, will probably be reshuffled. New mixtures tend to burn differently because species carry with them the fire-related traits that reflect their evolutionary heritage.

For example, some species, like trembling aspen, have moist, decomposable leaves that tend to reduce fuel load and fire hazard, while others, such as ponderosa pine, create a flammable fuel bed thanks to their long, resinous needles, which increase fire spread and intensity.

Climate change is usually described as an increase of a certain number of degrees over 50 or 100 years, implying slow, gradual change. The reality is that while the average changes slowly, the extremes fluctuate faster and more widely. A given forest might survive the climate conditions of the year 2090, but not if it's killed by a severe fire or insect outbreak in 2030. Feedbacks between disturbances such as fire and the uncertainty of what vegetation will come in afterwards compound the difficulty of predicting future patterns.

Researchers attempting the difficult task of linking models of climate, vegetation and fire at global scales — an exercise called "pyrogeography" — are finding not only high variability between models but sometimes not even agreement on overall trends.

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The uncertainty of how wildfires and climate change will interact can seem paralyzing. If scientists don't know what will happen, can society do anything at all? There are several positive steps that people can take.

First, simply recognizing that the future will be different is important for broadening society's perspective on how to manage wildlands. Some current laws and policies take a static approach that is increasingly disconnected from reality.

Second, wildfire management actions are highly likely to be adaptable even under a variety of future conditions. For instance, thinning of dense small trees and applying prescribed burning in fire-adapted native forests that have seen a century of fire suppression will increase the odds of conserving them as climate warms. Conversely, severe fires in ecosystems that have natural adaptations to intense burns should not be labeled "catastrophes," at least not in ecological terms.

Third, when wildland managers compare alternative management options, they should routinely apply models linking climate, vegetation and fire. Although models have many frustrating weaknesses, their purpose is not to provide a single correct answer but to show the range of relative differences, allowing stakeholders, such as the public, to debate more fairly about the mosaic of future landscapes on short and long timescales.

Future fire regimes will present many new situations that will range only from bad to worse — there is not a bright side to climate change in terms of conservation of native ecosystems. But even under the urgent threat of severe fires, we do have modeling tools, studies of effects of past climate fluctuations and ongoing research that can be applied now to make thoughtful decisions that recognize sources of uncertainty and seek to retain options for the future.

The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on LiveScience.