Wildfires across our hot planet

forest fire wildfire trees
Forest Fire / Courtesy U.S. Forest Service, U.S. Department of Agriculture

Laura Nielsen for Frontier Scientists

Wildfires are a hungry, terrible and complex force which we’ve long struggled to live alongside. Smoke and particulate matter from wildfires can travel thousands of miles, lowering air quality and causing health impacts. Local fires risk lives, and fire damage costs millions or more to repair. And now, conditions that bolster wildfire strength and magnitude are changing. How do humans and wildfires fit together within our transforming world?

Alaska wildfires
Extreme fire behavior in Alaska on July 1, 2004. Fires (outlined in red) continued to grow since mid-June, triggered by a few days of record-breaking lightning and encouraged by hot, dry, and windy conditions. Image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. / Courtesy NASA

Wildfires thrive when conditions are right. Earlier spring snowmelt, high air temperatures, low moisture content, and lingering conditions like drought can skyrocket the chances of wildfire.

Climate change and changing wildfire trends

Sound familiar? That’s because it is. Climate change enhances fire conditions. Heightened temperatures and hot air that is saturated with moisture are expected symptoms of global warming. The occurrence of ore extreme weather events is another symptom, like extreme storms. We’ve also noticed climate change creating lingering, long-lasting trends like drought by changing the way jet stream winds blow: meandering and slow, instead of speedy and streamlined.

These trends elevate fire risks, setting the stage for hot-burning uncontrollable wildfire. Hot moist air and a longer growing season due to earlier spring snowmelt allows plants to thrive, filling forests with future fuel including ‘ladder fuel’, understory brush. Ladder fuel lets fire easily climb to the forest canopy, where it can swiftly spread. Then extreme storms bring fast-blowing winds. Wind-fallen branches end up on the forest floor: future deadwood to fuel flames. Then climate trends might shift, bringing hot dry air or even drought. Forests dry out swiftly in the heat, priming them for a spark from lightning or human sources like agricultural burning. Hot, windy conditions spread the sparks.

Humans in the red zone

The world is a crowded place. In the last two decades, a quarter million people have moved into Colorado’s ‘red zones’, places highly susceptible to intense wildfires. The damage to life and property that results from a megafire is alarming. This year saw multiple lives and many acres destroyed by fires like the Black Forest Fire, the most destructive wildfire in Colorado history. Wildfires in the western United States are increasing in frequency and duration, accompanying a growing season that is 18-21 days longer since 1900. The United States have warmed 1.5°F overall since 1985. Alaska has warmed 2°F since 1985, and its growing season lasts an average of 30 days longer since 1900.

The U.S. Forest Service chief Tom Tidwell addressed the Senate Energy and Natural Resources Committee in June 2013. He stated: “On average, wildfires burn twice as many acres each year as compared to 40 years ago. Last year, the fires were massive in size, coinciding with increased temperatures and early snow melt in the West. The largest issue we now face is how to adapt our management to anticipate climate change impacts and to mitigate their potential effects.”

How do we fight fires?

Firefighters are seeing more frequent, hotter- and longer-burning fires, and because of warmer springs the fire season has grown longer by nearly 80 days in the last three decades. With more houses in danger zones, there’s more to protect. Yet budget cuts have hit the Forest Service hard. In 1991 fire suppression used about 13% of the agency’s budget; in 2012 fire suppression used nearly 50% of the agency’s budget. Yet the Forest Service’s fire suppression funds have been slashed by more than $500 million since 2010. Still they struggle on. Different tactics are employed. The Forest Service often allows natural fires in federal-owned forests to burn longer before quenching them, or to burn out naturally in a controlled manner, in the hopes of removing fuel sources that would otherwise linger for the next, bigger fire. Alternately, some invest in preemptive tactics that clear ladder fuels from old-growth forests, a tactic that firefighters praise as highly effective in preventing and stopping the swift spread of fire. By striving to manage forests according to the natural fire regime they are adapted to, the Forest Service hopes to keep both people and trees healthy.

elk fire widlfire Montana
Elks flee before an August 2000 wildfire in the Bitterroot National Forest, Montana, U.S. / Courtesy John McColgan, U.S. Forest Service, U.S. Department of Agriculture

It’s a neverending battle. Pest outbreaks like Pine Beetles, which kill off old-growth trees, create more fodder for the fires. Mountain forests in the southwest United States are failing to regenerate after wildfires because the local climate conditions have changed (especially the amount of precipitation). And far to the north where boreal forests blanket parts of Alaska, Canada and Siberia, “We expect another doubling to quadrupling of fire over this next century,” says Mike Flannigan, professor at the University of Alberta. “We attribute this — and I’ll be quite clear — to human-caused climate change.” The loss of great forest have dire consequences, since forests act as a carbon sink. Growing plants use and store carbon dioxide. Burning plants, however, release carbon dioxide, and forests are slow to recover. Far-north Arctic permafrost holds millenia-old carbon in rich layers of soil and ancient plant matter. As that permafrost thaws and becomes more susceptible to fire, the Arctic can turn from a carbon sink to a carbon source.

Wilfdires seen from space

In this video from NASA, the National Aeronautics and Space Administration, you can watch wildfires flare up around the world. NASA’s satellite-born MODIS sensors (MODerate Resolution Imaging Spectroradiometer) help inform continually-improving models which predict fire severity. MODIS sensors detect about 10,000 actively burning fires around the world on any average August day. It’s a clear reminder of the fire realities we face, and continually learn to live with.

Watch: NASA’s A Global Tour of Fire


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  • ‘A Look Back at a Decade of Fires’ National Aeronautics and Space Administration (2011)
  • ‘Black Forest Fire The Most Destructive In Colorado’s History’ National Public Radio (2013)
  • ‘Colorado Wildfire: Our Scorching Future?’ Tim McDonnell and James West, Mother Jones (2012)
  • ‘Fires Burn More Fiercely As Northern Forests Warm’ Dylan Walsh, Yale Environment 360 (2013)
  • ‘Forest Service Chief testifies on wildfire response capabilities, challenges’ U.S. Forest Service (2013)