Earth’s oceans have lost roughly 2% of their dissolved oxygen since 1960, and a new scientific review argues that loss is spreading fast enough, and interacting with enough other planetary systems, to deserve formal recognition as a tenth force capable of destabilizing the planet. The review, led by scientists at the Scripps Institution of Oceanography at UC San Diego, was published in the journal Limnology and Oceanography on June 30, 2026.
The researchers are not just cataloguing a chemistry problem. They are arguing that aquatic deoxygenation, the decline of dissolved oxygen across oceans, coastal waters, lakes, rivers and streams, already shows up inside the geologic record as a companion to Earth’s worst mass extinctions. Their case is that the modern version of that pattern is now running on the scale of decades rather than millennia.
Oceans Have Quietly Lost 2% of Their Oxygen Since 1960
The global figure sounds small. A 2017 assessment published in Nature found the oxygen content of the global ocean had fallen by more than two percent over five decades, with far steeper losses in specific basins and depths. Scripps Institution of Oceanography’s own research page on the subject lays out the scale in plainer terms.
- 2% of dissolved oxygen lost across the global ocean since the 1960s, according to Scripps Institution of Oceanography’s oxygen research page
- 4.5 million square kilometers of new low-oxygen water added to the open ocean over the same period
- 20 to 50% oxygen decline already recorded in the hardest-hit regions, including upwelling zones off California
- 1 to 7% additional oxygen loss projected globally by 2100 under current ocean models
Two mechanisms drive most of it. Warmer surface water simply holds less dissolved gas, a straightforward chemical fact. At the same time, a warming ocean stratifies into layers that resist mixing, so oxygen-rich surface water struggles to reach the depths. Nutrient runoff from farms and sewage adds a third driver, feeding algae blooms whose decomposition strips oxygen from coastal water entirely.
The Idea Was Born at a Climate Summit in Madrid
Lead author Erica Ferrer, a Scripps Oceanography alumna now a postdoctoral scholar at UC Santa Barbara’s National Center for Ecological Analysis and Synthesis, developed the paper’s core argument with senior author Lisa Levin, a Scripps biological oceanographer. The two conceived the project after attending COP25, the 2019 United Nations Climate Change Conference held in Madrid.
An assessment from the International Union for Conservation of Nature released at that same Madrid summit had already found that oxygen-starved coastal sites worldwide had grown from just 45 in the 1960s to roughly 700 by 2019. That finding sat behind the researchers as they built their case over the following years.
This is not a single paper appearing out of nowhere. Ferrer raised the idea in a 2023 paper of her own, and Rensselaer Polytechnic Institute ecologist Kevin Rose led a 2024 follow-up titled aquatic deoxygenation as a planetary boundary and key regulator of Earth system stability, co-written with Ferrer, Levin and researchers including fisheries ecologist Denise Breitburg. The new 2026 review, carrying ten co-authors across institutions in the United States, Canada and Europe, is the most complete version of that argument yet.
This study is designed to elevate the profile of aquatic deoxygenation as a global threat and show that it does not operate in isolation.
Ferrer said that in a statement describing the paper’s aim, adding that oxygen loss deserves the same institutional weight already given to carbon emissions and biodiversity loss.
Earth Ran This Experiment Once, at the End of the Permian
The geologic record already contains a version of this story, and it did not end well. Roughly 252 million years ago, the end-Permian mass extinction wiped out more than 95% of marine species, the worst die-off in the planet’s history. Research published in the journal Science modeling temperature-dependent hypoxia found that ocean warming during that period raised marine animals’ oxygen demand at the exact moment their oxygen supply was collapsing, a double squeeze that stripped away breathable habitat across entire ocean basins.
A separate, earlier oceanic anoxic event during the Toarcian, roughly 183 million years ago, produced a similar pattern tied to volcanism and disrupted carbon cycling. Scientists studying both events describe them as part of a recurring class of Phanerozoic-era anoxic episodes, greenhouse periods when the ocean’s chemistry turned against the life inside it.
The fossil record already holds a case study in delayed marine collapse from a different extinction entirely. Ammonites, the coiled cephalopods that filled ancient seas, survived the asteroid impact that ended the age of dinosaurs only to disappear entirely in the epoch that followed, undone by ocean conditions scientists are still working to fully untangle.
| Event | Timing | Ocean Oxygen Pattern | Outcome |
|---|---|---|---|
| End-Permian mass extinction | About 252 million years ago | Rapid volcanic warming triggered widespread ocean anoxia within at most tens of thousands of years | More than 95% of species lost; roughly 5 million years to recover |
| Toarcian Oceanic Anoxic Event | About 183 million years ago | Volcanism-linked anoxia sustained across ocean basins | Major marine extinction pulse |
| Modern aquatic deoxygenation | Since the 1960s, accelerating | About 2% of global oxygen lost already; regional declines of 20 to 50% | Unfolding over decades rather than millennia |
The comparison is not about magnitude. It is about speed. What geologists estimate took at most tens of thousands of years to trigger the Permian collapse is now playing out within a single human lifetime.
Nine Boundaries Rarely Break One at a Time
The framework Ferrer and Levin want to join was introduced in 2009 by Earth system scientists led by Johan Rockström. It defines nine processes that keep the planet within a stable, livable range:
- Climate change
- Biosphere integrity (biodiversity loss)
- Land-use change
- Freshwater change
- Biogeochemical flows of nitrogen and phosphorus
- Ocean acidification
- Atmospheric aerosol loading
- Stratospheric ozone depletion
- Novel entities, including chemical pollution
A 2023 assessment from the Stockholm Resilience Centre’s full quantification of all nine boundaries found six had already been crossed: climate change, biosphere integrity, land-use change, freshwater change, biogeochemical flows and novel entities. Only ocean acidification, ozone depletion and atmospheric aerosol loading remained within safe limits.
Rockström, who directs the Potsdam Institute for Climate Impact Research, said the update painted a troubling picture of the planet’s condition.
This update on planetary boundaries clearly depicts a patient that is unwell, as pressure on the planet increases and vital boundaries are being breached.
Katherine Richardson, the University of Copenhagen professor who led that 2023 assessment, compared the situation to blood pressure. Crossing six boundaries does not guarantee catastrophe on its own, she said, but it functions as a clear warning sign that risk is climbing. Ferrer and Levin’s argument builds directly on that logic: deoxygenation does not act as a tenth, separate item on the list. It functions as connective tissue between the other nine, worsening biodiversity loss, amplifying nutrient pollution and feeding back into the ocean’s ability to absorb carbon in the first place.
Whales, Fisheries and the Food Web Underneath Them
Deoxygenation’s reach extends well past fish that breathe water directly. Marine mammals that surface for air are exposed too, since low-oxygen water pushes their prey to relocate or vanish outright. Ferrer said the stability of the entire planet rests on the health of these aquatic systems.
The health and stability of our planet depends on the health and stability of aquatic ecosystems, which need oxygen to function normally, Ferrer said, describing the chain that runs from dissolved gas to whole food webs.
That chain runs directly into coastal economies. Fishing communities positioned near expanding low-oxygen zones face shifting catches as species move toward cooler, better-oxygenated water or decline where they stand. Coral reefs already stressed by warming and acidification lose additional resilience when oxygen drops alongside them, since reef organisms have little tolerance for compounding stressors arriving at once.
Could Ocean Oxygen Become the Tenth Planetary Boundary?
Getting a new item onto the official list is not automatic. Adding oxygen would require the Stockholm Resilience Centre’s planetary boundaries team, the same group behind the 2009 framework and its 2023 update, to agree on a quantifiable global threshold, the kind of single number that already exists for carbon dioxide concentration or nitrogen flow. Ferrer and her co-authors acknowledge that a definitive global figure for safe oxygen loss does not exist yet, though they argue current rates already exceed what most scientists would consider tolerable change.
Ferrer said formally recognizing the problem would help clarify its downstream effects on the planet’s overall stability, and that mitigating oxygen loss represents a critical piece of protecting both biodiversity and climate. The review’s authors frame their paper as a foundation for that quantitative work rather than the final word on it.
For now, the case rests on a pattern the Permian seas already wrote into rock: take the oxygen out of the water, and everything living in it eventually runs out of room.
Frequently Asked Questions
What Is Aquatic Deoxygenation, Exactly?
Aquatic deoxygenation is the decline of dissolved oxygen in oceans, coastal waters, lakes, rivers and streams. Oxygen enters water two ways, through surface mixing driven by wind and waves and through photosynthesis by phytoplankton and algae. Deoxygenation happens when organisms and bacteria consume oxygen faster than those two processes can replace it.
Is Ocean Deoxygenation the Same Thing as Ocean Acidification?
No. They are separate items on the Planetary Boundaries framework. Ocean acidification tracks falling pH as the sea absorbs excess atmospheric carbon dioxide, while deoxygenation tracks dissolved oxygen levels directly. The two often occur together since both stem from rising carbon emissions, but they measure different chemical changes with different biological consequences.
Which Ocean Regions Are Losing Oxygen the Fastest?
Earlier oxygen-tracking research found the Arctic, equatorial and North Pacific, and Southern Ocean regions account for roughly 60% of the total global oceanic oxygen loss recorded so far. Coastal upwelling systems, including waters off California, have also shown localized declines far steeper than the 2% global average.
Can Ocean Oxygen Loss Be Reversed?
Not quickly. Current ocean models project an additional 1 to 7% decline in global dissolved oxygen by 2100 even under existing warming trends, since deep-ocean ventilation operates on decades-to-centuries timescales. Slowing the loss depends largely on curbing the warming and nutrient pollution driving it in the first place.
Has Earth Had Ocean Anoxic Events Before the Permian?
Yes. Scientists have documented multiple Phanerozoic-era oceanic anoxic events beyond the end-Permian extinction, including the Toarcian event roughly 183 million years ago. Researchers describe these episodes as recurring features of greenhouse climate periods, when disrupted carbon cycling repeatedly pushed ocean chemistry into conditions hostile to marine life.
