Within northern Alberta, risks to regional landbird populations exist due to pervasive and intensive patterns of resource development. Industrial forestry and oil and gas exploration and extraction (conventional and oil sands) has raised concerns about the capacity of the boreal forest to absorb multiple, simultaneous disturbances. Although the effects of multiple stressors are often assumed to be additive (the impacts of two stressors are simply added together or =a + b), recent reviews suggest interactive effects (=a x b) in approximately 77% of studies leading to a major source of uncertainty for projections of biodiversity. We addressed this issue by examining the additive and interactive effects of forestry and energy stressors on boreal landbird density within the Athabasca Oil Sands Area. We used avian data (>2511 point counts from 279 survey areas), habitat data, and human disturbance data to create generalized additive models (GAMS) within sector groups (Forestry, Forestry-Energy, Energy). We included in our models multiple stressors associated with forestry, conventional oil and gas, and Steam Assisted Gravity Drainage (SAGD) development. The Forestry-Energy model group contained the best model for 17/30 (57%) of species while the Energy model group contained the best model for 13/30 (43%) species. For each of the 30 landbird species, the best model was an interactive model. Key stressors of importance within the best models included harvest units, wellsites, vegetated linear features, and roads. Comparing predicted density for landbird species between current and no disturbance landscapes revealed positive, negative, and neutral responses to multiple interacting stressors.
Dr. C. Lisa Mahon is the Boreal Landbird Biologist in the Prairie and Northern Region of the Canadian Wildlife Service, and Adjunct Professor at the Department of Biological Sciences, University of Alberta. She is project lead of Environment Canada’s cause-effects monitoring program to examine the effects of oil sands disturbance on boreal landbirds. Her work involves collaboration with partners to (1) develop methods to model relationships between landbirds and disturbance, and (2) implement studies to examine landbird response (patterns, mechanisms) to disturbance at local and landscape scales. Over the past 25 years she has studied habitat relationships of landbirds in coast-interior, sub-boreal, and boreal forests, grasslands, and agricultural lands in Western Canada.