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Forests are always changing. They're a very dynamic ecosystem.

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We've used data from the Landsat satellites

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to produce a comprehensive look at forest dynamics

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on the scale of human management and natural disturbances.

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Dark green pixels had no disturbances in the 25 years studied.

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Yellow shows where a disturbance happened in a particular year.

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At this scale, what really stands out are the large fires in the West

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and timber harvesting in the Pacific Northwest, Maine, and all across the Southeast.

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We need to know the rate of disturbance and how that rate is changing

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in order to understand how carbon is changing across the landscape.

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Here we can see the impact of policy decisions on forest dynamics

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The various protected areas around Broken Bow Lake

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remain largely undisturbed

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compared to the surrounding region,

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which flickers with the tell-tale patches of timber harvesting.

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Any disturbance, whether from fire or hurricanes,

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mining or logging, impacts how much carbon the forest can store.

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The southern and central Appalachian Mountains,

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from Tennessee to West Virginia,

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are home to most of the disturbances

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resulting from mountaintop removal mining.

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Throughout Appalachia, coal mining has been a big industry since the 1860s,

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and mountaintop mining became dominant over the last 30 years.

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The Hobet Mine in Boone County, West Virginia, existed before 1986

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and has continued to expand throughout the course of this study.

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The pattern we see at the Hobet Mine is

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replicated across the entire southern Appalachia.

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We mostly think of hurricanes wreaking houses,

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flooding cities, and endangering lives.

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But they can also damage forests,

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knocking down wide swaths of trees.

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Hurricane Hugo was a category 4 storm

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when it struck South Carolina in September of 1989,

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and the scale of the disturbance shows in the 1990 data.

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Four and a half million acres of forest

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were affected by wind gusts and storm surges of salt water.

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Disturbances of this magnitude

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can release large amounts of carbon dioxide

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into the atmosphere as the trees decompose.

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Tornadoes leave long tracks of damaged forests in their wake

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showing as a bright line in the satellite imagery.

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These long straight tracks are extremely distinctive of this type of disturbance.

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On Mother's Day in 2008,

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several tornadoes in Georgia left a track 150 kilometers long

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and about 2 kilometers wide.

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For many tree species in the Rocky Mountain West,

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fire is a natural part of their life cycle,

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clearing space for new growth on the forest floor

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and releasing seeds from their pinecones.

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But climate change is projected to increase

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the intensity and frequency of wildfires.

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In 1988, Yellowstone National Park

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endured the largest fire ever recorded there.

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Many individual fires combined to damage 36% of the park,

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burning for several months.

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The scale of the disturbance

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is apparent in the following year's disturbance map.

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Less than 30% of the burned area re-gained forest cover by 2008.

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and the rate of recovery across Yellowstone

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has been quite variable,

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depending on the fire intensity and local conditions.

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Forests have always dealt with

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outbreaks of insects that can damage trees.

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Northern Colorado, near Rocky Mountain National Park,

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did not have severe damage

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from Mountain Pine Beetle before 2003.

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But the damage starts appearing in 2004

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in low areas,

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and spreads to higher elevations over the next few years.

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Climage change might result in more frequent episodes

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and trees less able to withstand the stress,

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but this will vary from region to region.

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Forests are a dynamic ecosystem.

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And we need to know how fast they change

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and what is driving those changes if we ever hope

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to track how much carbon

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they're pulling out of the atmosphere

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and storing for us.

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The Landsat archive, and other remote sensing systems,