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In higher

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latitudes, forests are adapted to burn
about once every century.

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But with warmer temperatures
comes more fires.

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And why is this?

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Partially because of this stuff,
called duff, forest debris

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that slowly builds up on the forest floor,
about one inch every 17 years.

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And because of the cold winters,
it doesn't decompose.

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Alison: It doesn't have roots.

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So it's completely dependent
on relative humidity for moisture.

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So it actually dries very rapidly in warm,

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dry conditions
like we often have here in the summer.

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Narration: Which means of warmer temperatures, duff
becomes a potent fuel for fires.

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Alison: Most Alaskans are vulnerable
to wildland fire.

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And with climate change,
it seems that the imprint on

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the landscape is growing, and so more
and more communities are vulnerable.

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Dr. Hoy: When a wildfire comes through,
what we're really seeing is it's actually

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it's not just the trees that are burning,

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but it's the soil layer that's burning as well.

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And so when that fire comes through
and it burns that soil layer, it's

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like you're taking off the lid of a cooler
where everything is frozen below.

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And so as that soil comes off,
then we start to see the ground

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start to thaw and permafrost is thawing there.

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And so as we see those changes happening,

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we're actually creating
more climate change over time.

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So wildfires are releasing
carbon gases into the atmosphere.

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And then as permafrost thaws,
it too is releasing carbon

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gases into the air,
which then can create warmer conditions

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which can allow for more wildfire
and more thaw.

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So you really see this cycle
that continues up in boreal forest

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and Arctic areas over time.