Aerial surveillance and oil spill impacts based on beached bird survey data collected in southern British Columbia

Abstract

The cumulative impact of maritime oil pollution resulting from frequent but typically small oil discharges (i.e. <1000 L) is a significant issue worldwide, but this issue is difficult to address because of the size of the oil spills involved relative to the size of the environment into which they are released. Here we compare oil-spill patterns and surveillance-flight effort of the Canadian National Aerial Surveillance Program (NASP) with the proportion of oiled carcasses and beaches documented by Beached Bird Survey (BBS) programs conducted in several regions of southern British Columbia. BBS results from two regions (west coast of Vancouver Island and the Strait of Georgia) support the contention that NASP surveillance over adjacent waters has played a role in reducing the cumulative impact of small oil spills on marine birds. However, the proportion of oiled carcasses documented in other regions (south Vancouver Island, Vancouver Harbour and Boundary Bay) provides no support for the deterrence effect of NASP. The absence of a deterrence affect suggests that predominant maritime activities in these regions are not affected by NASP presence, because these activities may not have been targeted as potential oil pollution sources in the past. Our comparisons not only provide some evidence of the impact of NASP on oil discharges at sea, but also can serve to inform NASP or other enforcement agencies concerning where future effort could be most beneficial.