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Bark beetles and Rocky Mountain National Park


In the dry Interior West, the pine forests that dominate many landscapes can experience widespread mortality during outbreaks of bark beetles such as mountain pine beetle.

 

The animation below shows a recent outbreak occurring in and around Rocky Mountain National Park in the late 2000s.  The visitor map to the right shows the location.

(source: www.nps.gov/romo)

What do the colors mean?  In this false-color composite, denser forest appears green and open soil appears light pink.  Sparse forests contain a mix of trees, shrubs, dead branches, and soil, and thus appear as a mixture of greens, browns, and pinks depending on the amount of each.  Elevations above treeline appear bright pink and aqua.  Clearcuts also appear pink because they remove most vegetation, exposing bright soil that slowly fades back to green as vegetation grows back.

 

What about bark beetles?  Because tree needles turn red, then grey, and then drop to the ground, the greenish vegetation component of the colors disappears after bark beetles attack and only pinks and reds remain.  Thus, the bark beetle outbreak appears on the landscape as a dark red to pink blob that spreads over several years. 

How can we map the change?  Because the movies above are based on mathematical segmentation of the satellite time series, we have quantitative information about the timing and severity of the change caused by the bark beetles.  This allows us to pinpoint when a particular area on the ground showed its first sign of bark beetle attack, which we can map below. 

Another look! In addition to noting the year the beetles first show an impact, we can also compare the images before and after the outbreak to see cumulative impacts. The images below show how the forests looked before (on the left) and after the outbreak (middle). The map on the right identifies where change occurred for the whole Rocky Mountain National Park. 

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