In a transformative new study published in Science Advances, researchers affiliated with the Ocean Discovery League have revealed a stunning truth about humanity’s relationship with the deep ocean: we have visually explored less than 0.001% of the deep seafloor. This extreme underrepresentation is startling, especially considering that the deep ocean covers approximately 66% of the Earth’s surface. The study, led by Dr. Katy Croff Bell, offers the first comprehensive global estimate of deep-sea benthic visual observations, exposing both the vast unknowns lurking beneath and the alarming inequalities in global exploration efforts.
The deep ocean, typically defined as waters deeper than 200 meters, represents one of Earth’s largest and most essential ecosystems. It plays a fundamental role in regulating global climate, producing oxygen, harboring biodiversity, and even serving as a reservoir for biomedical discoveries. Despite its critical importance, direct visual observations of this environment remain incredibly sparse. Our understanding relies heavily on data derived from a limited number of submersibles, remotely operated vehicles (ROVs), and other imaging technologies that have only recently become more accessible and sophisticated.
The study compiled data from roughly 44,000 deep-sea dives conducted since 1958, across the waters of 120 countries. Despite this immense effort, the total visual footprint covers an area approximately the size of Rhode Island. To put this in perspective, it equates to only one-tenth the size of Belgium, a negligible portion compared to the vast expanse of the global seafloor. Researchers emphasize that even if their dataset underestimated exploration by an order of magnitude, visual coverage would still measure less than 0.01%. This massive gap presents significant challenges for marine science and informs conservation strategies.
A crucial insight from the study is how uneven and geographically biased these visual explorations have been. More than 65% of documented visual observations are clustered within 200 nautical miles of just three countries: the United States, Japan, and New Zealand. Broadly, five nations—the United States, Japan, New Zealand, France, and Germany—account for 97% of all deep-sea submergence observations. This narrow concentration heavily influences the characterization and generalizations made about the deep ocean’s ecosystems, raising concerns about the representativeness and completeness of current oceanographic knowledge.
Furthermore, the temporal distribution of exploration is skewed, with nearly 30% of the visual observations predating 1980. Early missions frequently yielded low-resolution, black-and-white still images that barely scratch the surface of modern scientific potential. Advances in imaging technology over the past decades have improved data quality significantly, yet exploration remains geographically and temporally limited. This historical context underscores how deep-sea exploration methodologies have evolved but also highlights the persistent technological and financial barriers limiting progress.
The study sheds light on habitat-specific knowledge gaps as well. While features such as submarine canyons and ridges have enjoyed relatively high investigatory focus, vast and ecologically critical environments like abyssal plains and seamounts remain grossly underexplored. These habitats are vital for global ecological functions, including nutrient cycling and carbon sequestration, and may harbor unknown species and ecosystems integral to ocean health. The lack of visual data impedes comprehensive understanding of these systems and their roles within the planetary biosphere.
Rising threats amplify the urgency of broader and more inclusive deep-ocean exploration. Climate change, deep-sea mining initiatives, and other forms of resource exploitation present imminent risks to these fragile and poorly understood ecosystems. Without sufficient baseline data, policymakers and conservationists lack the critical evidence needed to regulate and protect these environments effectively. Dr. Bell emphasizes that informed decision-making concerning resource management and ecological preservation hinges on expanding our exploratory reach.
Encouragingly, new technological innovations provide hope for overcoming some of the cost and accessibility barriers currently limiting deep-sea research. The emergence of miniaturized, more affordable deep-sea vehicles and imaging systems enables a wider range of researchers, including those from low- and middle-income nations, to contribute meaningfully to ocean science. This democratization of exploration tools holds promise for diversifying global participation and generating a more representative scientific picture of the deep seafloor.
The researchers call for coordinated, global scientific initiatives that prioritize filling the vast gaps in deep ocean visual coverage. Such efforts would enable the oceanographic community to develop more accurate ecosystem models and support the sustainable management of ocean resources. Enhanced collaboration would ensure that the diversity of seafloor habitats and regions is studied systematically, rather than relying on the limited datasets of a handful of countries. These strategies will foster a better understanding of the deep ocean’s complexities and vulnerabilities.
This study also serves as a sobering reminder of the magnitude of the challenges faced in ocean conservation. If the knowledge base for terrestrial ecosystems were limited to an equivalent proportion of land area, scientific assessments would be based on a region roughly the size of Houston, Texas. Such a comparative illustrates just how little we truly know about the marine underworld — the largest, yet most mysterious environment on our planet.
National Geographic Society Chief Science and Innovation Officer Dr. Ian Miller underscores the importance of involving local communities and scientists in deep-sea exploration. Empowering coastal regions with cutting-edge research technologies aligns with the goal of achieving a more inclusive and comprehensive understanding of the deep sea. Community-led exploration initiatives not only broaden the scope of scientific inquiry but also foster stewardship and conservation ethics rooted in firsthand knowledge and experience.
The Ocean Discovery League, founded by Dr. Bell, pursues an innovative mission to accelerate deep-ocean exploration through the development of accessible and cost-effective tools. Their approach combines technological innovation with targeted geographic strategies to expand the scope of mapped, imaged, and characterized seafloor areas. By lowering financial and technical entry barriers, they aim to involve a more diverse range of researchers, democratizing deep-sea science and expanding global knowledge.
Funding for this impactful research was generously supported by the National Geographic Society, Rolex Perpetual Planet Expeditions program, and the Cabot Family Charitable Trust. Their investment underscores the significance of deep-ocean exploration for understanding planetary health, guiding policy, and inspiring future generations of ocean scientists.
In sum, this pioneering study exposes a profound knowledge deficit in our grasp of the deep ocean’s vast and intricate seafloor. Meeting the looming environmental challenges confronting marine ecosystems requires a transformative expansion of visual and scientific exploration efforts worldwide. Only through equitable, sustained, and technologically empowered exploration can humanity hope to uncover the secrets of the deep seafloor and safeguard this critical component of Earth’s biosphere.
Subject of Research: Not applicable
Article Title: How Little We’ve Seen: A Visual Coverage Estimate of the Deep Seafloor
News Publication Date: 7-May-2025
Web References: http://dx.doi.org/10.1126/sciadv.adp8602
Image Credits: Ocean Discovery League
Keywords: deep ocean exploration, seafloor imaging, deep sea biodiversity, ocean ecosystems, visual oceanography, deep sea submersibles, marine conservation, oceanographic research, global ocean mapping, ocean policy, ocean technology innovation
