Syncrude Canada Ltd. and Suncor Inc. operate oil sands processing facilities in the Fort McMurray area that emit acidic emissions including sulphur, nitrous oxide and heavy metals. A study of the vegetation stress was conducted in a study area within the vicinity of the Syncrude Canada Ltd. and Suncor Inc. oil sands leases in order to document conditions in 2001. This is the fifth assessment of vegetation stress in the area since 1978. The study consisted of the interpretation of false colour infra-red (FCIR) air photographs with a nominal scale of 1:10 000, a field inventory to ground-truth the interpretation and final mapping of the extent of vegetation stress. The air photographs were obtained in early August and field inventories were conducted in late August of 2001.
Stress factors of insect infestations, disease, excess moisture stress (natural and man-caused) and fire were documented and ranked based on the amount of vegetation displaying symptoms of injury or stress. Trees and shrubs known to be sensitive to acidifying emissions, including trembling aspen, jack pine and alder were examined to document the extent of impact.
The overall vegetation health within the study area is good to very good, thus reducing the amount of stress from all causes. The major causes and areas of stress within the study area are:
• insect and disease damage (1 685 ha);
• natural moisture excess (191 ha);
• man-caused moisture excess (41 ha); and
• fire (1 777 ha).
Based on interpretation of FCIR photography and field survey, no visual evidence of vegetation stress related to air pollution was found within the study area.