Dueling climatic wildfire studies

It seems that for every alarming press release these days, we can find an opposite and equal reaction. Perhaps we should dub it the First (or maybe third) Law of Climate Skepticism. We have this from the National Science Foundation this week:

Press Release 11-193

Scorched Earth: The Past, Present and Future of Human Influences on Wildfires

Fires have continuously occurred on Earth for at least the last 400 million years. But since the 1970s, the frequency of wildfires has increased at least four-fold, and the total size of burn areas has increased at least six-fold in the western United States alone. Steadily rising, the U.S.’s bill for fighting wildfires now totals $1.5 billion per year.

How much of the increases in the frequency and size of fires are due to human activities? No one knows for sure.  But a paper in this week’s issue of the Journal of Biogeography puts the role of fire in natural ecosystems into context and provides support for efforts to plan for future risks from wildfires.

Produced by an international team of researchers, the paper presents a new framework for considering wildfires based on the Earth’s pre-human fire history, ways that humans have historically used and managed fire and ways that they currently do so. “We need to look into the past to understand our current and future relationship with fire activity,” says Jennifer Balch of the National Center for Ecological Analysis and Synthesis.

This research emphasizes the importance of understanding the relative influences of climate, human ignition sources and cultural practices in particular environments in order to design sustainable fire management practices that protect human health, property and ecosystems.

More information about this research, partially funded by the National Science Foundation, is provided in the accompanying interview with Balch, as well as in a press release issued by the University of California at Santa Barbara.

-NSF-

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Reading that, you’d get the idea that the only the supposed recent climate change drives wildfire increase, right? Welll…not so fast. There’s more to the story. First, I think wildfire data suffers from the same sort of technology and media driven statistical bias near the present as do thunderstorm and tornadoes. Second, just like with Mannian team insistence that trees are accurate treemometers, there are many other factors and drivers in play. Liebigs law rules the issue, and water is often the most influential factor rather than temperature. Read this press release from 2009 by the Ecological Society of America below. Emphasis mine.

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Plants Could Override Climate Change Effects on Wildfires

Paleoecological data reveal strong influence of vegetation changes on wildfire frequency

The increase in warmer and drier climates predicted to occur under climate change scenarios has led many scientists to also predict a global increase in the number of wildfires. But a new study in the May issue of Ecological Monographs shows that in some cases, changes in the types of plants growing in an area could override the effects of climate change on wildfire frequency.

Philip Higuera of Montana State University and his colleagues show that although changing temperatures and moisture levels set the stage for changes in wildfire frequency, they can often be trumped by changes in the distribution and abundance of plants. Vegetation plays a major role in determining the flammability of an ecosystem, he says, potentially dampening or amplifying the impacts that climate change has on fire frequencies.

“Climate is only one control of fire regimes, and if you only considered climate when predicting fire under climate-change scenarios, you would have a good chance of being wrong,” he says. “You wouldn’t be wrong if vegetation didn’t change, but the greater the probability that vegetation will change, the more important it becomes when predicting future fire regimes.”

Higuera and his colleagues examined historical fire frequency in northern Alaska by analyzing sediments at the bottom of lakes. Using meter-long samples, called sediment cores, Higuera and his colleagues measured changes in the abundance of preserved plant parts, such as pollen, to determine the types of vegetation that dominated the landscape during different time periods in the past. Like rings in a tree, different layers of sediment represent different times in the past.

The researchers used radiocarbon dating to determine the sediment’s age, which dates as far back as 15,000 years. They then measured charcoal deposits in the sediment to determine fire frequency during time periods dominated by different vegetation. Finally, they compared their findings to known historical climate changes.

In many cases, the authors discovered, changes in climate were less important than changes in vegetation in determining wildfire frequency. Despite a transition from a cool, dry climate to a warm, dry climate about 10,500 years ago, for example, the researchers found a sharp decline in the frequency of fires. Their sediment cores from that time period revealed a vegetation change from flammable shrubs to fire-resistant deciduous trees, a trend which Higuera thinks was enough to offset the direct effects of climate on fire frequencies.

“In this case, a warmer climate was likely more favorable for fire occurrence, but the development of deciduous trees on the landscape offset this direct climatic effect. Consequently, we see very little fire,” Higuera says.

Similarly, during the development of the modern spruce-dominated forest about 5000 years ago, temperatures cooled and moisture levels increased, which – considered alone – would create unfavorable conditions for frequent fires. Despite this change, the authors observed an increase in fire frequency, a pattern they attribute to the high flammability of the dense coniferous forests.

Higuera thinks this research has implications for predictions of modern-day changes in fire regimes based on climate change. These findings, Higuera says, emphasize that predicting future wildfire frequency shouldn’t hinge on the direct impacts of climate change alone.

“Climate affects vegetation, vegetation affects fire, and both fire and vegetation respond to climate change,” he says. “Most importantly, our work emphasizes the need to consider the multiple drivers of fire regimes when anticipating their response to climate change.”