Only 0.001% of the deep seafloor visually observed in seventy years, revealing gaps and bias in ocean exploration and global biodiversity understanding

(Press-News.org) (Saunderstown, RI — May 7, 2025) In a groundbreaking study published today in Science Advances, researchers from Ocean Discovery League reveal that only a minuscule fraction of the deep seafloor has been imaged. Despite covering 66% of Earth's surface, the deep ocean remains largely unexplored. The study, "How Little We've Seen: A Visual Coverage Estimate of the Deep Seafloor," is the first to document that, in decades of deep-sea exploration, humans have observed less than 0.001% of the deep seafloor. This total area is roughly the size of Rhode Island or one-tenth the size of Belgium.

The deep ocean, defined as being deeper than 200 meters, sustains diverse ecosystems and provides essential services, including oxygen production, climate regulation, and crucial pharmaceutical discoveries, and plays a critical role in maintaining the health of our planet. Yet, despite its importance, research into this immense ecosystem is severely limited, with visual surveys primarily focused on just a few regions and countries. Visual imaging is one of the most critical methods to study the deep seafloor and is one of the three key pillars of ocean exploration, alongside mapping and sampling.

"As we face accelerated threats to the deep ocean—from climate change to potential mining and resource exploitation—this limited exploration of such a vast region becomes a critical problem for both science and policy," said Dr. Katy Croff Bell, President of Ocean Discovery League, National Geographic Explorer, and lead author of the study. "We need a much better understanding of the deep ocean's ecosystems and processes to make informed decisions about resource management and conservation.”

Using data from approximately 44,000 deep-sea dives with observations conducted since 1958, across the waters of 120 different countries, the study is the most comprehensive global estimate of deep-sea benthic observations to date and highlights the disparity in global exploration efforts. Given that not all dive records are public, the researchers assert that even if these estimates are off by a full order of magnitude, less than one-hundredth of 1% of the seafloor would have any visual records. In addition, almost 30% of documented visual observations were conducted before 1980 and often resulted in only black and white, low-resolution, still imagery. 

Remarkably, over 65% of visual observations have occurred within 200 nautical miles of just three countries: the United States, Japan, and New Zealand. Due to the high cost of ocean exploration, a mere handful of nations dominate deep-sea exploration, with five countries— the United States, Japan, New Zealand, France, and Germany—responsible for 97% of all deep-sea submergence observations. This bias in geographic coverage and operator representation has led the oceanographic community to base much of its characterization of the deep ocean ecosystem on this incredibly small and unrepresentative sample.

The study also highlights the knowledge gap regarding seafloor habitats. Certain geomorphological features, such as canyons and ridges, have been the focus of significant research, while vast areas, including abyssal plains and seamounts, remain underexplored.

These findings underscore the urgent need for a more comprehensive and global effort to explore the deep ocean, ensuring that scientific research and conservation efforts accurately reflect the true extent of the seafloor. As noted in the study, if the scientific community were to make all assumptions about terrestrial ecosystems from observations of only 0.001% of that total area, they would be basing their assessments of all land-based life on Earth on an area roughly the size of Houston, Texas.

To address these challenges, the researchers call for expanding exploration efforts and utilizing emerging technologies to increase access to the deep ocean. With advancements in smaller, more affordable deep-sea tools, there is an opportunity to broaden the scientific community’s reach, including low- and middle-income nations in ocean exploration and research.

“There is so much of our ocean that remains a mystery,” says Dr. Ian Miller, Chief Science and Innovation Officer at the National Geographic Society, which contributed funding for this work. “Deep-sea exploration led by scientists and local communities is crucial to better understanding the planet’s largest ecosystem. Dr. Bell’s goals to equip global coastal communities with cutting-edge research and technology will ensure a more representative analysis of the deep sea. If we have a better understanding of our ocean, we are better able to conserve and protect it.”

This study represents a crucial step in understanding the gaps in ocean exploration and the need for comprehensive global strategies to ensure the protection and sustainable management of the deep ocean. The authors hope these findings will encourage more scientific collaboration, leading to a deeper understanding of our planet's most vital ecosystem.

Funding for this study was provided in part by the National Geographic Society and Rolex Perpetual Planet Expeditions program and the Cabot Family Charitable Trust. 

About Ocean Discovery League
Founded by deep-sea explorer Dr. Katy Croff Bell, Ocean Discovery League's mission is to accelerate deep-ocean exploration by developing accessible systems to broaden the community of those who explore and understand the deep sea. ODL is developing a strategic approach to expand the area of the seafloor that is explored, mapped, and characterized while reducing expenses by creating lower-cost, easier-to-use tools, technology, and training. These actions, combined with a more targeted approach to selecting exploration locations, will expand deep-sea exploration to a broader community of researchers and explorers.
 
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