Geospatial analysis of oil discharges observed by the National Aerial Surveillance Program in the Canadian Pacific Ocean

Oil pollution resulting from day to day human maritime activities contributes a high portion of the overall input into marine environments, constituting a major threat to marine ecosystems worldwide. In Canada, the National Aerial Surveillance Program (NASP) extensively monitors and collects information on oily discharges using remote sensing devices. Despite the availability of data from NASP and other surveillance programs internationally, there is a paucity of spatial analyses of oil pollution patterns, particularly in their association with human marine pursuits. The objective of this paper is to analyze the association between observed oily discharges and human maritime activities in the Canadian Pacific Ocean. This study used Poisson regression to spatially model detected oily discharges with marine traffic, coastal facilities and proximity to coast. Further, it developed localized ('regional') models to address spatial heterogeneity. The models identify recreational activities, passenger traffic, commercial traffic, fisheries, and proximity to the coast as predictors of observed oily discharges. The regional models yield more accurate and reliable estimates of local associations, and identify more parsimonious sets of predictors for each region. By identifying and accounting for human activities most associated with oily discharge patterns, the models developed in this study could be used to estimate pollution rates in areas with less surveillance, and identify areas where NASP coverage may need to be increased. Spatially explicit rates estimated by these models can be used to monitor the effectiveness of programs and policy aimed at reducing discharge rates of oily pollution. This study can be used as a model approach for extending the analysis to the other coasts of Canada, using available NASP data.