Mountain pine beetle populations in Jasper National Park have declined for the first time in six years, according to a survey conducted by Natural Resources Canada.

The survey examined how well the beetles had reproduced and colonized in the trees they had attacked.

Scientists sampled 25 sites in the park. After completing the survey in May, they found the mortality rate of the populations they examined was 98 per cent.

"This is really the first year that we've had significant decline in the population," said Roger Brett, lead researcher of the study.

Brett said he has been mapping mortality rates of pine beetles in Jasper for six years and has never seen populations decline like this. Normally, they would double from one year to the next, he said.

Delayed development, cold snap

The mountain pine beetle has devastated more than 16 million hectares of forest in B.C. and Alberta.

The insects burrow into pine bark and mine the phloem, the layer between the bark and the wood. After the eggs hatch, the larvae feed under the bark, which makes the trees turn red and die.

Brett said the decline was not only due to a cold winter, but also to a delayed mating season. In 2018, larvae were produced from mid-July to September. Normally, they would be produced from July to August.

"That doesn't help the population at all, because the younger immature larvae ... they're not as cold tolerant as more mature larvae, so when you do end up getting the cold snap, it'll affect them a lot more," Brett said.

Red trees will persist

According to Parks Canada, 163,000 hectares of forest in Jasper National Park have been infected by the mountain pine beetle.

"Those larvae were all killed over the winter, but the trees they were in are also dead, so we will see an expansion of that total area impacted this summer," said David Argument, the resource conservation manager for Jasper National Park.

According to Parks Canada, 163,000 hectares of forest in Jasper National Park have been infected by mountain pine beetles. (Wallis Snowdon/CBC)

"But those trees that are turning red now won't produce a new crop of adult pine beetles to continue that expansion," he said.

Kim Mumby works at the Whistle Stop Pub in Jasper. She said tourists are often shocked when they see the sweeping hills of red trees in Jasper.

"It's just devastating for everyone to watch year after year because it just seems to get worse," Mumby said.

Populations also drop outside Jasper

Erica Samis, director of forest health and adaptation with Alberta's Ministry of Agriculture and Forestry, said February's cold snap negatively impacted beetle populations outside Jasper.

Based on the province's recent survey, Samis said, high mortality and low reproduction rates for pine beetle were seen in areas such as Slave Lake, Lac La Biche, Whitecourt, Edson, Hinton and Grand Prairie.

"Whether this will lead to a specific decline in population around the province, we'll just have to wait and see until the fall," she said. "But it is some good news for us, that's for sure."

Problem not solved

But scientists say the problem is not over.

Brett said the high mortality rate only applies to the areas that were sampled and not to all affected areas in Jasper National Park.

"This number has got to be taken with a very large grain of salt," he said. "It's going to vary in different parts of the park."

"Mountain pine beetle outbreaks do periodically experience very high levels of mortality," said Allan Carroll, a professor of insect ecology and the director of the forest sciences program at the University of British Columbia.

"In the absence of 100-per-cent mortality, there are still going to be beetles building up their numbers if conditions are conducive to that," said Carroll.

"Now there's an opportunity to really hit them hard by the way of management activities, because this is the chance to kick them while they're down," said Carroll.

The beetles could bounce back and rebuild their populations, Brett said.

"So we have to remain vigilant. We can't just sit back and say it's done and there's no more mountain pine beetle."