Mountain Pine Beetle and Climate Change

 

Supplemental Resources:

 

 

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Notes regarding MPB & Climate Change

 

MPB - Basic Facts

 

MPB - Current Outbreak

 

How Climate Change Has Affected the MPB

 

 

How the MPB has Affected Climate Change

 

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Questions for CHLY radio

 

1) How significant is the current infestation of MPB compared to others in the past – either MPB or other forest insect pests?

Historically MPB is the most destructive insect pest of BC's forests - even western forests of NA for that matter.  Most of the time it occurs at very low levels - attacking only stressed, over-mature lodgepole pole pine trees.  During outbreaks it can successfully attack healthy pine trees.  The current infestation is an order of magnitude greater than any previous outbreak.  The current outbreak started in about 1999/2000.  It has now affected a total of about 17.5 million hectares.  The rate of infestation in this area ranges from light to severe.

2) The area affected by MPB is huge, how does this compare with the area that is logged in BC each year?

Each year less than 1/3 of 1% of the area of BC is harvested.  This amounts to ~300,000 ha - as compared to the 17.5 million ha of area infested by the MPB.  The current area that has been attacked is 50x's larger than what is harvested on an annual basis.

3) I assume that there are number of factors that have contributed to the extent and intensity of the MPB outbreak over the past several years.  Can you give me an overview of what they are?

As an overview, 2 factors have significantly contributed to the current outbreak: amount of host material and climate. 

Successful fire fighting efforts over the last 60 years have contributed to a significant increase in the amount of mature lodgepole pine in BC.  In fact there is (was) 3x's the amount of mature lodgepole pine than there was in the early 1900's.

A warmer, drier climate favors the survival MPB.

4) Focusing now on climate change: which aspects of our changing climate have contributed to the recent success of the MPB?

There are two aspects of primary concern: temperature and moisture.

The MPB (and all insects) are cold-blooded.  Their development and activity are directly affected by temperature.  Average annual temperature dictates where the MPB can just survive and where it can thrive and do well.  Simply put BC can be divided into 3 zones regarding the MPB: 1) climate inhospitable - where MPB generally does not survive, except in milder years, 2) climate benign - where MPB survives and gets along just fine; outbreaks occur but are small in area and short-lived, 3) climate favorable - where MPB does quite well, occasional outbreaks occur over large areas that can last 5-10 years.  Recently the area of climate inhospitable has been decreasing and areas of climate benign and climate favorable have been increasing.

In addition to the need for "sufficient heat" to develop and "do well", there is the factor of winter mortality.  Generally speaking, winter temperatures of -35-40C can substantially kill the over wintering brood.  Alternately, an early or late cold snap of -20C in the fall or spring can do similar damage.

Lately, we have seen slightly warmer  temperatures all year and NO significant cold snaps.  Thus the successful development of MPB has been favored AND significant winter mortality has NOT occurred.

Further to this, summer conditions have also favored the MPB.  One factor is the temperature in August.  This is when the new adult beetles take flight from the brood tree and seek a new host.  Average daily temperatures above 18C favor a mass flight.  We have had these summer temperatures lately.  It takes a mass attack of the beetles to overcome a tree's defense mechanisms.  Recent temperatures have favored mass attack conditions.

A second factor is summer precipitation.  Low precipitation favors the beetle in 2 ways: 1) the MPB is a weak flyer and does not do well with summer rains, 2) summer drought also stresses the pine - inhibiting its ability to pitch-out the beetle.  Thus low summer precipitation favors the colonization period of the beetle.

5) We now have a vast area – millions of hectares - of MPB damaged forest.  I’ve only seen pictures of it from space or from the air.  What does it actually look like on the ground, say in comparison to an area impacted by a forest fire or by intensive harvesting?

Well, forest fire or harvesting have the effect of removing much of the trees from the landscape - BUT these disturbance events are limited in their geographic extents.  Damage by the MPB, on the other hand, does not directly remove the trees from the landscape.  Granted they may be removed by subsequent harvest or forest fire, but the MPB leaves the dead trees standing.  Instead they are left to decay over the next few decades.  Also, this recent attack covers an area 5x's the size of Vancouver Island.  It is massive beyond words.  Fresh kill is the most apparent as the foliage is a bright red.  Trees that have been dead for 2 or more years are a pale gray and tend to fade from view.  As time passes the forestland will recover - the newly regenerating forest will re-green the landscape.

6) MPB damage must have implications for present and future climate change.  Can you talk about those implications for a minute?

This is a new area of study and not much in the way of empirical data is available.  There are 3 processes we need to consider regarding climate and carbon from these forests: 1) photosynthesis (converts CO2 into sugars, starches and wood), 2) wood decay ( slow process that is the reverse of photosynthesis) and 3) fire (a quick and "violent" reverse process of photosynthesis).  Presently boreal forests act as a small carbon sink (photosynthesis and tree growth > decay + fire).  However, the recent outbreak of the MPB has converted the lodgepole pine forests of BC from a carbon sink to a carbon source.  The impact of the current outbreak (modeled for 2000-2020) has been the release of ~270-320 megatonnes of carbon (990 Mt of CO2 equivalent) into the atmosphere.

7) We, as a society, are doing very little, so far, to reduce our impact on the climate.  The climate will continue to change, so we can probably anticipate more forest pest outbreaks like the MPB.  What can the forest industry and/or the provincial or federal governments do to avoid – or at least minimize – a comparable outbreak in the future?

Indeed we can expect more outbreaks of forest pests.  The problem is potentially two-fold: 1) in some areas climate change will put a stress on the trees and 2) the altered climate (warmer & drier) can favour the insect (increase survival and increase their range. 

A few other forest insect pests of concern in BC include the spruce beetle (the MPB equivalent on spruce trees in the interior of BC), the spruce budworm (which actually attacks Douglas-fir in BC) and the forest tent caterpillar (which dines on hardwoods).

What can the forest industry do?  Well, there is not much you can do with a large epidemic - except salvage some of the wood.  THE most effective time to manage for an insect pest is during the building stage, when the population is just starting to climb.  So monitoring populations closely an an annual basis is very important.  Luckily we have been doing that for several decades in BC.  Once a population is "on the rise" it is critical that we act very quickly.  Unfortunately in BC we have not always been very good at that.  Usually funding is the issue.  The government needs to be willing to devote funding to managing insect outbreaks at the earliest stages.

Last, it is critical that we grow forests that can thrive in an environment with climate change.  This is the realm of silviculture.  We need to grow and promote healthy forests so they will be more resilient to attack.