Natural Elements, NRCan's Monthly Newsletter

Landscape Features Affect Beetle Settlement Patterns

<Marring vistas of the Peace River region of British Columbia>

The gulleys and dissecting ridges perpendicular to a primary ridgeline have epidemic infestations of mountain pine beetle on their south-facing slopes. (Photo source: Jordan Koopmans)

Recent research by Natural Resources Canada’s (NRCan) Canadian Forest Service (CFS) has revealed that landscape topography plays a key role in the eastern spread of the mountain pine beetle epidemic from interior British Columbia toward northern Alberta. While the wind was known to carry the beetles, it was uncertain whether topography influenced where they settled.

“One of the primary findings of this study was that the orientation of valleys with more mountain pine beetle infestations was parallel to the dominant wind directions. This means that valleys may act as corridors for spreading the insect into the region,” says Honey-Marie de la Giroday, a CFS Forest Research Technician who is conducting the research as part of her Master’s thesis. 

The work is being led by CFS scientists at the University of Northern British Columbia (UNBC) in Prince George, British Columbia. Using detailed mountain pine beetle inventories from local forestry companies, Honey-Marie and CFS research scientists Brian Aukema and Allan Carroll have examined the beetle’s movements in the Peace River region of northern B.C. between 2004 and 2006, the years when the epidemic first hit the region.

<Newly developed adult mountain pine beetles> Adult mountain pine beetles in their natal gallery prior to dispersal from the host tree.

The scientists coupled this data with a specialized computer algorithm — the topographic position index — that classifies the region according to the various landforms. This approach allowed Honey-Marie to use an advanced statistical technique — spatial point process modelling — to examine how landscape features affected beetle migration.

“I’ve been able to demonstrate that certain landform types, in the first three years of infestation, have greater occurrences of mountain pine beetle infestations,” says Honey-Marie. Landscape features with the most influence were small-scale canyons, large valleys and windward slopes of mid-slope ridges.

These findings will help the development of new strategies to combat the spread of many invasive species, and not just insects but plants as well. In the case of the mountain pine beetle, knowing the roles played by specific landforms and directionality could enable pre-emptive thinning of tree stands and other forms of control. Improved options for pest control of the mountain pine beetle are increasingly important because populations of the insect established on the eastern slopes of the Rocky Mountains continue to threaten the jack pine of Alberta’s boreal forest.

“When an organism, whether invasive or native, spreads epidemically, finding ways to predict where it could establish in a region and the potential extent of its range is very important in managing and mitigating that problem,” says Honey-Marie. 

The next step in the research is to examine the dispersal patterns of the mountain pine beetle, including long-distance migration versus short-distance migration from year to year. Future projects will include the effects of climatic variables such as temperature and precipitation. 

To learn more, contact Honey-Marie at honeydel@nrcan.gc.ca or Brian at Brian.Aukema@nrcan.gc.ca. For information on other CFS projects, visit Forest Research.