As Alberta conducts annual aerial surveys of its forests, the province’s forest expert says she expects they’ll start to see the signs of drought — including more mountain pine beetles.
This year’s surveys, which started on Aug. 15 and run until Sept. 15, come after extremely dry weather hit the province throughout the summer.
“Drought has a variety of effects on the forests and obviously on the insect population,” said Erica Samis, manager of forest health and adaptation with Alberta Agriculture and Forestry. “When a tree is drought stressed, it can’t withstand attacks.
“It’s a lot easier for the beetles that are attacking that tree to get in and also the defences, when the beetles are inside, are lower so the beetle has a much greater success in a tree that is stressed by drought.”
Hot, dry conditions could also have other consequences for forests.
“With drought, you can often get fires too,” said Mike Flannigan, professor with the department of renewable resources at the University of Alberta.
Throughout Western Canada, there have already been hundreds of wildfires. A total of 6,484 fireshave already taken place across the country this year, up from a 10-year average of 5,761. They have burned more than 3,820,000 hectares — 172 per cent more than normal.
Flannigan, who’s also the director of the Western Partnership for Wildland Fire Science, said multiple stressors are critical for the health of forests.
“A forest can take a bit of insects or disease but then you put drought on top of that and the total is greater than the sum of the parts,” he said, noting that’s the danger for Alberta’s forests. “Throw in climate change, which arguably influences pests like mountain pine beetle and fire and drought, this is kind of a double or triple whammy.
“There will be more hot and dry years that will lead to more drought, bugs and fire. That’s a lethal combination for forests.”
Alberta’s pine beetle infestation began in southwestern Alberta in 2002 when the beetles flew in from British Columbia, assisted by wind currents flowing east.
Samis said the beetles have been almost absent in the southern parts of the province in recent years, but there’s still an active beetle population in areas up north such as Peace River and Grande Prairie.
They’ll know better whether that’s changed this year once they finish their aerial surveys, as well as ground work to inspect the trees.
“We can see on the ground how many trees there are attacked,” she said.
Samis added that the hot, dry weather can also have an impact on Aspen trees.
“It’s the canary in the coal mine,” said Samis, noting they have a program with the Canadian Forest Service that looks at the health of Aspens. “They show the signs of drought fairly early on so, for the past few years even, we’ve been seeing an increase in Aspen die-back so stands of Aspen are starting to die off.”
For example, she said she was driving to Drumheller recently and the normally full, green deciduous trees were starting to shrivel up and turn brown because of a lack of moisture — which starts to slow their growth and build up reserves for the wintertime.
Samis said most trees throughout the province are stressed.
“Trees that were healthy are seeing red or brown needles and starting to die off,” she said. “Not only does the forest feel the effect, but backyard trees … and shelter belts and natural stands used for windbreaks.”