Bark Beetles in Colorado
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According to experts on the subject, trees under stress from old age and drought are
more likely to be damaged by bark beetles.  However, the numbers of beetles have been
growing due to warmer temperatures especially since they have normally been controlled by
the very cold winter temperatures in the mountains.  In recent years the winters have just
not been cold enough to kill them off, so the trees can be attacked by huge swarms of
beetles.  In fact,
this news story from the University of Colorado at Boulder says that
the beetles now have a long enough warm, active season to produce extra generations thus
intensifying the problem. The news story was based on
this study of the Colorado beetles.

See
this for Forest Service information about infestations in Arizona and New Mexico.

According to the information at the above link, a tree that has been attacked will start to
turn reddish-brown within a month.  It seems that the color can vary with specific type of
beetle and time since infestation, as seen in the images
here (from similar infestations in
California).  There are more pictures and information
here.

These beetles have been attacking far and wide, as told in
this NY Times story. That
includes Colorado where all susceptible pine trees are expected to be gone in a few years.  
Although drought and old age can make trees susceptible, even healthy trees can be
successfully attacked by a large enough swarm of beetles, and there is a reason why these
swarms have been growing larger.  The winters are no longer cold enough to keep the
numbers down.

This ties the bark beetle problem to the warming climate.  At least
there is reason to
think climate change is part of the problem.  This may be an example of infestations by
various pests that have been forecast to occur with climate change.

The forests may regenerate as they do after fires, but that assumes that there will be
no more pest outbreaks to interfere.  
There have been forecasts of increased infestation by various plant-damaging pests with
the warming climate.  The pine bark beetle that has been killing millions of trees in the
western US and Canada l
ooks like an example of this.  I became interested in this after
noticing forests with as many dead trees as live ones on
two recent trips through Colorado.

Here are some pictures I took.  Below the pictures, you will find some more discussion and
some links.

CLICK ON THE PICTURES FOR LARGER VERSIONS. USE THE BACK BUTTON TO
RETURN.  

TREES AFFECTED BY BEETLES ARE COLORED RED, BROWN, OR SOME SUCH COLOR..
THE PICTURES TO THE RIGHT ARE ZOOMS ON PORTIONS OF THE PICTURES ON THE LEFT

I saw these trees from an overlook at the big reservoir south of Dillon and Silverthorne,
Colorado.  These towns are on I70 just a few miles west of the continental divide.  At the top,
the nearby trees seem OK, but the ones across the first bit of water are not.  Signs posted in
the area attributed the problem to the beetles.  I can't tell about the health of the very
distant trees, but their color doesn't seem to be very good.
Here, also at the Dillon Reservoir,
there is a problem with some of
the foreground trees.  I can't
quite tell about the trees on the
mountainside in the distance, but,
again, the color doesn't look good.

The dead trees could increase the
fire hazard in the area.
I got closer to these trees.  They are along US Highway 6 on the approach to Loveland Pass from
the west.  This highway climbs rapidly from the Dillon area to the roughly 12,000 foot altitude of
the summit of Loveland Pass, and I noticed scenes like this most of the way.

I did not edit the color, brightness, contrast, etc of any of the above pictures.  I did crop them and
reduce their memory size, but I did nothing else to them.
 I did edit the following pictures by
enhancing the colors.  However, the they do show the colors as I saw them.


I also saw many forests in Colorado that looked healthy, but this beetle is expected to spread.  See
more information below.
This picture is from a trail near Loveland Pass (11,990 ft) looking down toward Interstate 70,
which is the highway at the bottom of the valley below going right and left.  The closer highway
is US 6 descending from Loveland Pass.  This is the east end of the Eisenhower Tunnel, which is
just out of the picture to the left.  
I TOOK THE PICTURES BELOW IN 2011, A YEAR LATER THAN THE ONES
ABOVE. IN 2011, THEY WERE CLEAR CUTTING THE DAMAGED AREAS
SINCE THE BEETLE-DAMAGED TREES WERE DRIED OUT AND
REPRESENTED A FIRE HAZARD.
Clear cutting the beetle-damaged areas near the Dillon Reservoir. In the right-hand picture, notice
many more discolored trees in the distance.
Bark from some of the cut trees near the Dillon Reservoir with holes where beetles bored
through.
Another group of damaged trees near the Dillon reservoir.  The damage seems to have advanced
farther than just colored leaves.