The Devastating Spread of the Mountain Pine Beetle

When the mountain pine beetle began blazing a path across forests in British Columbia and Alberta, nobody could have imagined the extent of the damage to come. But as the insect devastated pine forests and disrupted communities, forest industries, recreational use, watersheds, and plant and wildlife habitats, the problem became disturbingly clear. Now, as the beetle creeps into the boreal forests of the Northwest Territories and Saskatchewan, with a real concern it may reach as far east as the Maritime provinces, researchers at the University of Alberta have responded to calls from government, industry, non-profit organizations and the general public to help conserve and protect an invaluable national resource at the heart of Canadian identity.

Anatomy of an invasion

Mountain pine beetles are tiny, about the size of a grain of rice. The hard-shelled insects spread by flying, aided by wind currents. At its core, their ability to destroy trees is rather simple: the beetles starve the tree of nutrients, and the fungi they carry grow into the wood and disrupt water transport.

The pine trees die in three stages, which can take up to several years: green, when the trees have been infested but their needles look normal and healthy; red, after the beetles have overcome the trees’ defences, and a change in needle colour indicates that the trees are dead; and grey, when the beetle has moved on and the needles have fallen away. A native to the pine forests of western North America, at lower-density population levels, the mountain pine beetle has played an important role in lodgepole and ponderosa pine forest renewal. It’s only when populations reach epidemic levels that we see large-scale mortality of forests.

mpb-life-cycle
Stages of the Pine Beetle Infestation

By 2006, the mountain pine beetle had breached the Rocky Mountain barrier in a big way, flying and being carried in air currents over long distances to establish in the Peace River district of northwestern Alberta. Here, the lodgepole pine that makes up much of the historic habitat for mountain pine beetle hybridizes with jack pine, a species whose range stretches all the way to the Maritime provinces. Given this fresh territory, it only took a few years for the mountain pine beetle to spread eastward across this hybrid zone in Alberta, successfully establishing in genetically pure jack pine and knocking at the doorstep of Saskatchewan’s northern forests. In the last couple of years, mountain pine beetle has even spread northward as far as the 60th parallel.

Making the leap:

In 2011, it was a University of Alberta-led research team that determined the mountain pine beetle had invaded jack pine forests in Alberta, opening up the possibility for an infestation stretching east across the Prairies all the way to the Atlantic.

Working with Alberta Sustainable Resources Development and the Canadian Forest Service, a group of U of A tree biologists and geneticists discovered that as the mountain pine beetle spread eastward from central British Columbia, it successfully jumped species from its main host, the lodgepole pine, to the jack pine. Tracking the progress of the mountain pine beetle infestation across the province, they found the insect in jack pines as far east in Alberta as Slave Lake, 200 kilometres north of Edmonton.

Confirming the pine beetle’s jump to another species was good news from a research perspective, but it also revealed a serious threat—a potential Canada-wide invasion. Jack pine is the dominant pine species in Canada’s boreal forest. Its range extends east from Alberta all the way to the Maritime provinces.

Map of Mountain Pine Beetle Spread Across Canada

The end of an endless sea of trees

Two years ago, Department of Renewable Resources discovered that the beetle, in addition to attacking North America’s lodgepole and jack pines, was threatening to wipe out the remaining population of Alberta’s whitebark pine—a tree endangered across North America. Their research showed that climate change was causing temperatures to rise in the cold mountain elevations where the whitebark pine grow, creating ripe conditions for the destructive beetle to spread.

Department of Renewable Resources is looking at the susceptibility of whitebark pine to mountain pine beetles and warming climate in western North America, including Alberta. The goal is to evaluate whether the defences of whitebark pine are compromised due to increasing global warming. The tree species had already been decimated by white pine blister rust, a fungal infection carried from Europe 100 years ago.

There are a small number of trees that have resistance to the fungal disease, but they are concerned that the mountain pine beetle will kill them off. Areas that were historically climatically unfavourable to the beetle are becoming better for them, even at higher elevations and northern latitudes in Alberta.

The whitebark pine grows in high elevations along the Rocky Mountains through to the coastal ranges in western North America, including Alberta, British Columbia, Montana, Idaho, Washington and California. The tree can live up to 1,000 years. It provides nutritious seeds crucial to the diet of birds, black bears and grizzly bears, and is often the last species at the treeline, where it regulates snow melt and stabilizes shallow sub-alpine soils in the mountains.

Current Infestation of Mountain Pine Beetle in North America

Department of Renewable Resources studied the life history traits of the mountain pine beetle in whitebark pines, exploring the question of how well the insect reproduces in this type of pine. Even though the tree isn’t as well suited to the beetle here because of Alberta’s cooler climate, the insect is still capable of killing whitebark pines and will still produce large broods in the oldest, most developed of these trees. In both the short and long term, it means the mountain pine beetle will kill more of these trees.

Whitebark pine, made more vulnerable than lodgepole pine due to white pine blister rust, has consequently been listed as endangered by the Committee on the Status of Endangered Wildlife in Canada. The Canadian wilderness has been described as an endless sea of trees, but the notion that this rugged, remote ecosystem could go extinct in our lifetime is startling.

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