Science looks beyond the pine beetle to a landscape of pests in B.C. forests
Credit to Author: Derrick Penner| Date: Mon, 02 Sep 2019 21:35:42 +0000
While British Columbia’s timber industry is occupied with the mountain-pine-beetle infestation’s aftermath, forest managers haven’t lost sight of other pest problems looming among the trees in a changing climate.
News this summer has been dominated by mill closures and production cuts as companies adjust to timber supplies depleted by the unprecedented infestation that killed off pine trees in up to 18,000 square kilometres of forests.
At the same time, the province is closely watching an outbreak of spruce beetles chewing through trees across hundreds of square kilometres of forests to the north and east, Douglas fir beetles are wreaking havoc in Cariboo forests around Williams Lake and 100 Mile House along with other pests such as the spruce bud worm.
“We wouldn’t expect (the spruce beetle infestation) to be at the same scale as the mountain pine beetle,” said entomologist Jeanne Robert. “That said, this is a large outbreak, so we are going to keep monitoring it very carefully.”
Robert added that scientists believe the spruce-beetle infestation peaked in 2017 when it spread across 3,420 square kilometres of northern-interior forests. In 2018, the spread was smaller at about 2,420 square kilometres. The estimate for 2019 won’t be complete until November, she said.
Aerial surveys are the province’s front-line tool for keeping tabs on all things related to forest health, said Robert, regional entomologist for the Ministry of Forests, Lands and Natural Resource Operations in the Omenica and North East region.
That includes all bark beetles, such as the mountain pine, spruce, Douglas fir and western balsam beetles — all close relatives — and are all natural disturbances in forest ecosystems, Robert said, so she cautioned that it is difficult to characterize the outbreaks “as all bad.”
Insects on the attack: The discoloured trees in the landscape above are indicative of an infestation of the spruce beetle, a bark beetle that is a close relative to the mountain pine beetle. The beetles are a normal part of forest ecology but a warming climate has created conditions that have allowed larger-than-usual outbreaks. Photo: Ministry of Forests, Lands, Natural Resource Operations and Rural Development
In smaller-scale outbreaks, bark beetles attack the oldest and sickest trees first, Robert said, which helps open gaps in forest cover to allow for new trees to grow and increase a forest’s diversity of species.
“This is actually how ecosystems have evolved into what we see today (in B.C. forests),” Robert said, “which is very useful for humans.”
It is a combination of factors, however, ranging from insects to forest fires that forest managers, First Nations and timber companies need to worry about, said Allan Carroll, director of the forest science program in the University of B.C.’s department of forest and conservation sciences and a professor in insect ecology.
“But the one big bow that can be wrapped around all of this is the issue of a warming environment,” Carroll said.
The mountain pine beetle, for instance, took hold so well and in areas it had never been before because interior forests rarely experience the deep winter cold snaps that normally kill the insects off, keeping them in check, Carroll said.
Then the large number of dead trees left over from the infestations contributed to a buildup of fuels in forests for successive years of record forest fires.
And fire-damaged trees became susceptible to pests such as the western spruce bud worm, which weakened forest stands making them less resistant to more damaging threats, such as the Douglas fir beetle.
“Forests and forest ecosystems are so super complex that things that happen at one point in time can have an echo effect for many, many years — decades — to come,” Carroll said.
Professor Allan Carroll, an expert in insect ecology and director of the forest sciences program in the University of B.C.’s department of forest and conservation sciences.
In response, Carroll said scientists are learning that people need to focus on how to re-establish resiliency in forests, which will require considerable patience.
That will include planting tree species and mixes of species of trees that are better able to withstand the stresses of warmer, drier weather expected in the future.
“(But) the point at which it needs to resilient is not going to be in our lifetimes, it’s a long-term prospect,” Carroll said.
Shorter-term fixes will be in how foresters manage timber harvesting and silviculture to control, to the best of their ability, the impact of pest insects and how, by killing off trees, they can create the accumulation of fuels that exacerbate wildfires, Carroll said.
Foresters have had successes though, Carroll said.
In Alberta, for instance, authorities “have applied state-of-the-art science” to isolating and slowing the spread of the mountain pine beetle after it crossed the Rocky Mountains in the mid 2000s.
Carroll added that if they can keep that effort up, evidence suggests the population of beetles will crash before they spread into Canada’s vast tract of northern boreal forests.
Then in B.C., scientists are using the latest developments in pheromone science to tackle the spread of the Douglas fir beetle.
“Again, we have all the tools needed to manage (the beetles),” Carroll said.
So the forest ecologist remains hopeful, though his students sometimes call him Dr. Gloom, and his hope lies in the potential of those students to affect the change needed to make forests more dynamic and resilient.
That means viewing forests not just for the timber they provide for industry but managing them to provide clean water, the sequestration of carbon and the biodiversity that humans need to build healthy ecosystems.
“We don’t have that luxury of treating our forests as these static portfolios of timber as we have done so in the past,” Carroll said.