A recent global analysis by SkyTruth has estimated that 1.58 million km² of ocean surface is covered by oil slicks annually. The report highlights that over 90% of the estimated pollution occurs within national waters, often near coastlines. However, limited satellite coverage, particularly on the high seas, leaves substantial areas of the ocean unmonitored.
The analysis reveals that approximately 81% of the attributable annual oil slick area is associated with vessels, including AIS-tracked and 'dark' vessels. Tankers and cargo vessels are the dominant vessel types associated with the slicks. According to Karl Wuster, Chief Technology Officer at SkyTruth, oil pollution is a constant, global issue that happens far more often than the spills that make headlines.
The global analysis maps chronic oil pollution from vessels and offshore oil industry infrastructure, identifying where pollution is concentrated and which fleets are associated with oil slicks. By combining satellite imagery with data from SkyTruth's Cerulean platform and Sentinel-1 radar imagery collected between 2023 and 2025, the analysis provides a global picture of where chronic oil pollution is concentrated.
The report states that pollution is concentrated around major maritime and oil-producing regions, with some of the highest concentrations found in the Red Sea, Persian Gulf, Mediterranean, and Black Sea, off the western coast of Africa, and in waters surrounding Indonesia. The analysis also revealed that 75% of marine protected areas generally have lower slick concentrations than surrounding waters.
Despite this, sensitive marine mammal habitats remain affected by oil pollution, including porpoise and dolphin habitats in the Southeast Black Sea, and critically endangered Rice's Whale habitats in the Gulf of Mexico. The report warns that these areas require attention and enforcement to mitigate the impact of oil pollution.
The analysis identified 16 individual vessels that appear to be associated with oil slicks in more than 10% of observed satellite passes, alongside several offshore facilities, particularly off Indonesia and Nigeria. Additionally, the analysis examines vessel ownership and corporate accountability, finding significant gaps in beneficial-ownership information that can make it difficult to identify the companies ultimately connected to vessels associated with chronic oil slicks.
The report was released during Climate Week NYC, alongside SkyTruth's event Turning Geospatial Data into Action on Pollution and Climate, held on the sidelines of UNGA 81 in New York City. The findings raise questions about flag-state oversight and monitoring, particularly for flags of convenience disproportionately associated with oil slicks, including Palau, Panama, Malta, and Cyprus.
Key points
- Oil slicks cover 1.58 million km² of ocean surface annually, with 90% occurring within national waters.
- Vessels, including AIS-tracked and 'dark' vessels, are associated with 81% of the attributable annual oil slick area.
- Sensitive marine mammal habitats, including porpoise and dolphin habitats, remain affected by oil pollution.
