*Free* The vast majority of global marine oil pollution is due to human activity

The fraction of marine oil pollution caused by human activity may have been significantly underestimated, according to a new study, which uses satellite images to identify and map more than 450,000 ocean oil slicks worldwide. Oil pollution can have catastrophic and long-lasting impacts on marine biology and ecology. However, while much more is known about the impacts of large, punctuated oil discharges, far less is known about the extent and impact of small-scale oil releases. Ocean oil slicks – microscopically thin ephemeral layers of hydrocarbons floating on the ocean’s surface – can have natural and anthropogenic sources. In some cases, hydrocarbons can naturally seep from seabed oil reservoirs. Others can be attributed to oil discharge from ships, offshore oil/gas infrastructure, and coastal runoff. Due to their transient nature and the vast expanse of the ocean’s surface, monitoring marine oil slicks, particularly those caused by human activities, has been difficult. As such, estimates for the contribution of natural versus anthropogenic sources is poorly understood and highly variable. Contributions to oil slicks from natural seeps, for example, range from roughly 10% in the 1980s to 46% in 1990-1999, with contributions from anthropogenic sources even harder to pin down. A baseline understanding of global oil slicks is important for ocean conservation and policy. Using more than 560,000 synthetic aperture radar images (SAR) taken by the Sentinal-1A/1B satellites between 2014 and 2019, Yanzhu Dong and colleagues created a global map of oil slicks. SAR – a remote sensing method widely used in monitoring oil spills – allowed Dong et al. to identify and catalog static and persistent sources of marine oil slicks. The authors found a cumulative oil slick area of roughly 1.5 million square kilometers (km) – more than twice the area of France. Dong et al. identified a highly uneven distribution of slicks. The vast majority were located within 160 km of coastlines and along shipping routes. Using their analysis, Dong et al. estimate that the overwhelming majority of marine oil slicks (94%) stem from human activity. The remaining 6% are attributable to natural sources. In a related Perspective, Ira Leifer discusses the study’s findings further.

A live YouTube event discussing “Oil at Sea: How much is too much?” will be held on Thursday, 16 June, at 12:00 PST / 15:00 PM EST / 21:00 European Central Time.
Drs. Ira Leifer and Beril Sirmacek will discuss ocean resiliency / fragility and the implications of human-caused oil in the ocean. 
Moderation by Dr. William Kallfelz