Deep roots

The one theory Trump gets wrong about forest management

Forest fires keep burning up across the globe. A new study underscores an aspect of forest management that everyone has missed.

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Since mid-August, 4 million acres of forest have burned in California. As the blazes continue across the American West, researchers have plainly stated that not has this fire season been strengthened by climate change, but the situation is only going to get worse.

President Trump's response has been to downplay the role of climate change, and instead focus on forest management to help fight fires using strategies like clearing dried leaves and planting trees.

But a new study reveals why Trump's proposed solution may be missing the point. The key to understanding forest fires and their impact on the climate may not be the trees, so much as the soil and ecosystems in which they grow.

In a new study published in Nature Climate Change this week, researchers examined 417 burn sites in six regions in Canada and Alaska across 2004 to 2015. They found that vegetation plays a crucial, previously under-appreciated role in how fires spread, and how they may be predicted in the future.

Recent fires in California have been devastating.

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This runs contrary to the popular belief that weather events, like drought, and the seasons play a major role in what burns, by how much, and the consequences for the environment.

Forests are complex ecosystems, Xanthe Walker, a researcher at the Center for Ecosystem Science and Society at Northern Arizona University, says. If we are to understand them — and the fires that destroy them — then we need to consider the carbon stored in the soil, as well as the trees.

“We were surprised that fire weather and the time of year a fire starts proved to be poor indicators of carbon combustion. It's really about the fuels that are there when a fire starts," Walker said in a press statement.

Much like hurricanes, fires' strength and power depend on a number of factors. When looking at the best ways to combat a fire, forest rangers and firefighters alike look at fire weather, which can be measured by the National Wildlife Coordinating Group's Fire Weather Index. The index looks at precipitation, wind, and temperature in order to calculate a fire’s viability.

The elements that can make up an FWI.

National Wildfire Coordinating Group

All of those factors are important. But Marc-André Parisien, a research scientist with the Canadian Forest Service and co-author of the study, thinks this research adds an important fourth component: vegetation.

The fuel burned in boreal forests is a combination of below-ground organic soils, dead organic matter on the soil surface, and herbaceous and woody vegetation. These living and dead elements of any forest all play crucial roles in their ever-changing ecosystems. Now, scientists realize they play a role in their destruction as well.

There are "self-regulating feedbacks between fire and vegetation that can stabilize or destabilize regional fire regimes," the study authors say. And these "determine the direction of the feedback between increasing wildfire emissions and climate warming," they note.

"When we think of climate change and wildfires, we often instinctively think of extreme weather conditions. But our study shows that vegetation also matters — a lot! Predicting future vegetation is a tough nut to crack, but this study emphasizes the need to keep chipping away at it," Parisien said in the press release accompanying the research.

Breaking the monotony — There are four types of forest in the world, with boreal forests the most familiar to folks in the northern hemisphere. They’re built to withstand cold temperatures years around, like the spruce trees of Maine and the Western hemlocks of Alaska.

"While only a few tree species occur in the boreal forest, its enormous."

But people make the mistake of thinking of these forests as a “monotonous stretch," Sander Veraverbeke, assistant professor at Vrije Universiteit Amsterdam and co-author of the study, said.

"While only a few tree species occur in the boreal forest, its diversity in ecosystem structure, forest age, topography, peatland occurrence and permafrost conditions is enormous,” Veraverbeke says.

Essentially, the study highlights it is perhaps impossible to completely manage a forest and have it still be a forest. These places are wild and micromanaging them to the point where every black spruce can only age a certain number of years in a certain soil during certain climate conditions runs contrary to the very nature of a forest.

“We'll never be able to manage all of vast boreal biome — nor should we want to,” Parisien said.

Forests are ultimately uncontrollable. But scientists hope that their vegetation can be managed.

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But better establishing how these fires to vegetation conditions may help fight and even prevent these fires from occurring in the first place. That strategy may prove more ecologically sound, too, than the tree-planting strategy proposed by Trump.

The team behind this study hopes to work with NASA and other space agencies to better map fine-scale ecosystem variation. Bringing Earth-focused satellites on-board will enable scientists to better drill down into “what targeted actions, such as fire management or modifying forest vegetation, we can take to limit carbon loss," Parisien said.

Abstract: Carbon (C) emissions from wildfires are a key terrestrial–atmosphere interaction that influences global atmospheric composition and climate. Positive feedbacks between climate warming and boreal wildfires are predicted based on top-down controls of fire weather and climate, but C emissions from boreal fires may also depend on bottom-up controls of fuel availability related to edaphic controls and overstory tree composition. Here we synthesized data from 417 field sites spanning six ecoregions in the northwestern North American boreal forest and assessed the network of interactions among potential bottom-up and top-down drivers of C emissions. Our results indicate that C emissions are more strongly driven by fuel availability than by fire weather, highlighting the importance of fine-scale drainage conditions, overstory tree species composition and fuel accumulation rates for predicting total C emissions. By implication, climate change-induced modification of fuels needs to be considered for accurately predicting future C emissions from boreal wildfires.

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