DURHAM, N.C. – The vast size of the ocean makes tracking human activity there challenging, but a new study, published Jan. 4 in Nature, provides a startling glimpse of how extensive this activity has become in recent years and how much of it occurs outside of public monitoring.

Among other findings, the new analysis reveals that about 75% of the world’s industrial fishing vessels are not being publicly tracked, with much of this “hidden” fishing taking place around Africa and south Asia.

More than 25% of transport and energy vessel activity is also missing from public tracking systems.

Offshore energy development, much of it previously unmapped and undisclosed, has surged.

From 2017 to 2021, the number of oil platforms in coastal waters grew by 16%, while the number of wind turbines in those waters more than doubled. By 2021, turbines outnumbered oil platforms, with China leading the way with a ninefold increase in offshore wind production.

“A new industrial revolution has been emerging in our seas undetected—until now,” said David Kroodsma, director of research and innovation at the nonprofit Global Fishing Watch and co-lead author of the study.

“On land, we have detailed maps of almost every road and building on the planet. In contrast, growth in our ocean has been largely hidden from public view. This study helps eliminate the blind spots and shed light on the breadth and intensity of human activity at sea,” Kroodsma said.

“The footprint of the Anthropocene is no longer limited to terra firma,” said Patrick Halpin, professor of marine geospatial ecology at Duke University’s Nicholas School of the Environment, who co-authored the study. “Having a more complete view of ocean industrialization allows us to see new growth in offshore wind, aquaculture and mining that is rapidly being added to established industrial fishing, shipping and oil and gas activities.

“Our work reveals that the global ocean is a busy, crowded and complex industrial workspace of the growing blue economy,” Halpin said.

Researchers from Global Fishing Watch, Duke, the University of Wisconsin-Madison, the University of California-Santa Barbara and the environmental nonprofit SkyTruth analyzed 2 million gigabytes of satellite imagery collected from 2017 to 2021 to detect vessels and offshore infrastructure in coastal waters across six continents where more than three-quarters of industrial activity is concentrated.

By synthesizing GPS data with five years of radar and optical imagery, the researchers were able to identify vessels that failed to broadcast their positions. Using machine learning, they then concluded which of those vessels were likely engaged in fishing activity.

“Historically, vessel activity has been poorly documented, limiting our understanding of how the world’s largest public resource—the ocean—is being used,” said co-lead author Fernando Paolo, senior machine learning engineer at Global Fishing Watch. “By combining space technology with state-of-the-art machine learning, we mapped undisclosed industrial activity at sea on a scale never done before.”

While not all boats are legally required to broadcast their position, vessels absent from public monitoring systems, often termed “dark fleets,” pose major challenges for protecting and managing natural resources.

Researchers found numerous dark fishing vessels inside many marine protected areas, and a high concentration of vessels in many countries’ waters that previously showed little-to-no vessel activity by public monitoring systems.

“Publicly available data wrongly suggests that Asia and Europe have similar amounts of fishing within their borders, but our mapping reveals that Asia dominates—for every 10 fishing vessels we found on the water, seven were in Asia while only one was in Europe," said co-author Jennifer Raynor, assistant professor of natural resource economics at the University of Wisconsin-Madison. “By revealing dark vessels, we have created the most comprehensive public picture of global industrial fishing available.”

The study highlights the potential of this new technology to tackle climate change. Mapping all vessel traffic will improve estimates of greenhouse gas emissions at sea, while maps of infrastructure can inform wind development or aid in tracking marine degradation caused by oil exploration.

The open data and technology used in the study can help governments, researchers and civil society identify hotspots of potentially illegal activity, determine where industrial fishing vessels may be encroaching on artisanal fishing grounds, or simply better understand vessel traffic in their waters.

“Previously, this type of satellite monitoring was only available to those who could pay for it. Now it is freely available to all nations,” said Kroodsma.

Other authors of the new paper were Tim Hochberg, Pete Davis and Luca Marsaglia of Global Fishing Watch; Jesse Cleary of Duke; Sara Orofino of the University of California-Santa Barbara; and Christan Thomas of SkyTruth.

The work was funded by Oceankind, Bloomberg Philanthropies and National Geographic Pristine Seas.

CITATION: “Satellite Mapping Reveals Extensive Industrial Activity at Sea,” Fernando Paolo, David Kroodsma, Jennifer Raynor, Tim Hochberg, Pete Davis, Jesse Cleary, Luca Marsaglia, Sara Orofino, Christian Thomas and Patrick Halpin; Nature, Jan. 4, 2024. DOI: https://doi.org/10.1038/s41586-023-06825-8.