Oil in Canadian Waters: Identifying Significant Ecological Areas Vulnerable to Chronic Oil Pollution in Canada’s Coasts. Norma Serra-Sogas 1 , Stephanie Blazey 1 , Rosaline Canessa 1 , Patrick O’Hara 2 , Stefania Bertazzon 3 1 Geography Department, University of Victoria, Victoria, BC, Canada 2 Birds Oiled At Sea Program, Canadian Wildlife Service, Sidney, BC, Canada 3 Geography Department, University of Calgary, Calgary, AB, Canada normaserra@gmail.com Abstract Chronic oil pollution from commercial and recreational vessels is known to be a significant threat to marine and coastal ecosystems. Studies suggest that location and timing are key players when assessing the effects of oil pollution in any environment. To identify the areas where chronic oil pollution presents the greatest threat, we mapped and analyzed the spatial interaction between selected significant ecological areas (for example, designated Important Bird Areas) and estimated probability surfaces of oil spill occurrence for the Pacific, Maritimes and Great Lakes regions. The end results are a series of vulnerability surfaces representing the relative risk that a particular sensitive area will be exposed to oil pollution. This study aims to assist programs such as the Birds Oiled At Sea (BOAS) and the National Aerial Surveillance Program (NASP) in allocating their resources by highlighting and prioritizing areas in need of more monitoring and enforcement of compliance. 1 Introduction The successful management and conservation of marine and coastal environments depend on recognizing and understanding the impact that human activities have on different marine environments (Ban and Alder, 2008). A number of studies have employed mapping techniques to determine the location of vulnerable marine ecosystems to sea-based activities, regionally (Hiddink et al., 2007) or globally (Halpern et al., 2008), and by evaluating multiple threats (Ban and Alder, 2008) or by analyzing the spatial interaction of single species and threats (Zacharias and Gregr, 2005). Zacharias and Gregr (2005) define vulnerability as “the probability that a feature (i.e., ecosystem or single species) will be exposed to a stressor to which it is sensitive” while sensitivity is “the degree to which a marine feature responds to [a] stress […] measured using one or more indicators (of species, communities, and habitats) that respond to one or more natural or anthropogenic stressors” (p. 88). At the same time, vulnerability can be evaluated based on the spatial scale, frequency and the effects that a threat has on an ecosystem or species, the resistance of an ecosystem or species to a threat, and the resilience or recovery time of the ecosystem or species impacted (Halpern et al., 2008). In this study, we use Geographic Information Systems (GIS) spatial modelling and mapping capabilities to identify marine areas potentially vulnerable to small but chronic levels of oil pollution from vessel operations in Canada's Pacific and Atlantic 1 1 We refer to the Atlantic region as those marine and coastal waters adjacent to following provinces: Quebec, Nova Scotia, New Brunswick, Prince Edward Island and Newfoundland and Labrador. regions and based on the location of potential sensitive sites. Chronic oil pollution from commercial and recreational marine vessels is known to be a significant threat to marine and coastal ecosystems worldwide (Group of Experts on the Scientific Aspects of Marine Environment Protection, 2007), and particularly to seabird species as demonstrated by data collected from organized Beached Bird 852