Colorado’s Forests and the Pine Beetle Epidemic

Colorado’s Forests and the Pine Beetle Epidemic


the mountain pine beetle has been
attacking force for millions of years this cycle is different this one is
unprecedented both in its intensity at a site and also in its geographic extent
this thing goes from New Mexico a thousand miles north to the Yukon
Territories from the Front Range of Colorado to the Pacific Ocean this thing is already 10 times bigger
than the second biggest epidemic in history and people are wondering why is
this one so big Coloradans want to know what the next
forest will look like over the next hundred years
what will this turn into scientists at the University of Colorado
are working to find answers to these questions
Jeff mitten and Scott Ferranberg are trapping pine beetles and documenting
attacks on trees just east of the Continental Divide they are finding that
longer warmer growing seasons and persistent droughts make the trees more
vulnerable to pine beetles trees are killed as female beetles bores through
the bark to lay their eggs Scott look a bark beetle is just starting a new a new
hole now I can see I just saw the bark beetle go into that hole yeah I can see
them too there’s another one here job when
beetles attack a tree it’s a green tree when they mass attack it within a few
days water is no longer moving up carbohydrates are no longer coming down
it’s effectively dead but it looks perfectly healthy for another 10 months
to 12 months the following summer in July it begins to turn red like some
of the trees around us the tree needs water for everything but one of the
primary uses of the water and certainly the primary defense is that the water is
turned into resin and the resin is stored in resin canals in the bark and
that is what the bark beetle severs when it goes tunneling into the tree we go
Jeff look at these darkened up ready to fly if the tree is beautifully healthy
an enormous flow of resin will actually push it out foresters say it’s being
pitched out its pitch tossing the beetle out that’s the defense of the tree some
people have asked how many bark beetles does it take to kill a tree and the
answer is it’s incredibly variable if a tree is healthy and it’s got all the
water that it needs there are documented cases where two thousand beetles will
hit a tree all of them get pitched out and the tree survives the entire attack
if it doesn’t have enough water the resin pressure goes down
it can only put out a little bit of resin the beetle has no problem with
that and the beetle calls in more and more and they collectively sense we’ve
won and that tree is a donor does drought or
climate change have something to do with it it certainly does Jeff and Scott have
compared their observations of beetle activity in May and June with records
from the University of Colorado’s Mountain Research Station where
climatologist have been closely tracking daily temperatures for decades it gets
warmer and drier during the summers now the temperature is particularly changing
in spring before July 1 and so if it’s hotter and drier this is a more
susceptible tree so then instead of perhaps 800 beetles needy needed to kill
this tree perhaps only 200 or needed to kill them if it gets really drought
stressed a couple dozen can kill it all right let’s see how it goes in
addition one of the consequences of the change in summer temperature is the bark
beetle life cycle has really changed to three and four decades ago the bark
beetles started coming out in July there was a pulse of them the second and the
third week in August one two and their offspring would get out of the tree the
following year at about the same time a female bark beetle can lay about 60 eggs
what Scott and I have found is that the bark beetles now are starting much much
earlier this year when did you catch the first beetles May 22nd May 22nd instead
of the first few coming out in July and that’s fully two months earlier
furthermore we catch them later we catch them as late as September 20th so the
season is fully twice as long as it used to be and we saw last year that the ones
that can start early their offspring are out in August not 12 months later two
months later as a consequence a female that can start in June has 60 offspring
and then her offspring each have about 60 so that’s 60 offspring plus 3600 in a
year and so the season is much longer the beetles are now starting in May
instead of in July so the reproductive potential is exponentially greater than
it’s been before because at least some of the beetles are pulling off two
generations per year we think this is one of the reasons that this epidemic is
unprecedented in scale and intensity within about five years almost every
large lodgepole in the state will be killed
the mountain pine beetle has affected more than 3 million acres of forests in
Colorado I’m studying the regeneration that’s following this intense mountain
pine beetle outbreak even though we have a death the death of a mature forest we
want to know what is going to help create a new forest we are not seeing a large number of new
lodgepole pine seedlings coming in the understory of this dead forest what we
are seeing the subalpine fir and in species that grow better in the shade
which will be a very different forest than the pine forests were used to
we will also most likely see an increase in Aspen in many areas where Aspen is
currently existing it could take 30 40 50 years for those trees to reach the
height of the current forest however it is a different force there will be logs
strewn all over the ground I think that soil moisture and climactic conditions
will be the most influencing factor in the regeneration of our future forests
we’re in that midst of a long-term drought a very dry period drought
conditions are not favorable to any tree species and so the lack of regeneration
of tree seedlings could largely be due to extremely dry conditions I think one
of the things to reflect upon is that we are no longer talking about the
possibility of climate change this began decades ago and now what we’re seeing is
one of the major changes we’re seeing an epidemic that is just completely
unprecedented we talk a lot about stopping the increase in carbon dioxide
but as of yet we haven’t done anything

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