Sustainability Climate Change

Humans responsible for more oil slicks than previously thought

“What’s compelling about these results is just how frequently we detected these floating oil slicks.”
Oil in water
The Associated Press/ Dave Martin

Story at a glance


  • Measuring the extent of oil slicks on the earth’s oceans can be difficult due to changing wind patterns, tides, and currents.

  • New satellite imaging technology employed by a team of researchers helped chronicle how many slicks are human-induced.

  • Scientists hope effective regulations, similar to those adopted after the 2010 Deepwater Horizon spill, will be implemented in other affected areas.

Oil spills may be one of the more consequential and tangible examples of humans’ impact on the natural environment, as photographs of slicked marine life and vegetation helped spur calls for improved ocean conditions following major incidents throughout the 2000s. 

Since 1969 at least 44 oil spills of over 420,000 gallons each have affected U.S. waters, while thousands of smaller spills occur each year, according to National Oceanic and Atmospheric Administration (NOAA) data.  

A byproduct of oil spills are oil slicks, or microscopic thin layers of oil on the ocean’s surface. These can also be caused by other human activities like boating. 

Previously, it was estimated around 50 percent of oil slicks in the ocean resulted from natural causes and the remainder from human sources.

However, using satellite imaging technology, a group of researchers from the United States and China concluded a significantly higher proportion of chronic oil slicks – over 90 percent – are caused by human activity. 

Winds and currents are constantly moving oil slicks while waves break them down and can dissipate the slick further. These factors hinder large-scale investigations of oil slick prevalence, researchers explained. 


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But satellite technology poses a potential solution to monitor ocean oil pollution, especially in waters where human surveillance is difficult, explained study author Yongxue Liu, a professor at Nanjing University’s School of Geographic and Oceanographic Science.

To conduct the study, scientists used artificial intelligence to assess over 560,000 radar images taken from 2014 to 2019. Over 90 percent of slicks identified were within 100 miles of coastlines. 

“What’s compelling about these results is just how frequently we detected these floating oil slicks — from small releases, from ships, from pipelines, from natural sources such as seeps in the ocean floor and then also from areas where industry or populations are producing runoff that contains floating oil,” said Ian MacDonald, a professor in the Department of Earth, Ocean and Atmospheric Science at Florida State University, in a press release

Notably, fewer slicks were found in the Gulf of Mexico compared with other waters, likely due to reforms put in place following the 2010 Deepwater Horizon Oil spill.

This finding suggests government regulation, enforcement and oil platform compliance reduce leakage from wells operating in the area.

“If we can take those lessons and apply them to places globally, where we have seen high concentrations of oil slicks, we could improve the situation,” MacDonald said.

Oil has harmful effects on plankton, fish, whales, sea turtles, birds and other marine life.