Imagine the ocean completely lifeless—no whales, no fish, not even the tiniest plankton. What would that mean for our climate? A new study from Nature Communications explores this extreme scenario to understand how marine ecosystems shape the climate system—and the results are striking. Without ocean life, atmospheric CO₂ would rise by 50%, dramatically accelerating global warming.

“We have long understood that the biological carbon pump plays a crucial role in keeping atmospheric CO₂ levels low. However, most studies have overlooked the interaction with Earth’s ecosystems,” said Jerry Tjiputra, lead author of the study. “Our research suggests that land ecosystems compensate if marine life is eradicated and the ocean’s ability to absorb CO₂ is thus limited.”

For the study, researchers used a high-resolution climate model—the Norwegian Earth System Model (NorESM)—to simulate a planet where the ocean is biologically dead. Their goals were to isolate the role marine organisms play in absorbing and storing human-caused carbon emissions.

Marine organisms, especially plankton, absorb carbon dioxide near the surface through photosynthesis. When they die, their bodies sink, taking carbon with them to the deep ocean in a process known as the biological carbon pump.

This natural system has helped the ocean absorb about 25% of human-made CO₂ emissions, buffering the effects of climate change. But what if that pump were turned off?

To find out, the team ran two simulations:

• One with marine ecosystems functioning normally.
• One where all marine life was removed.

In the lifeless ocean scenario, CO₂ levels in the atmosphere surged by 50% compared to the realistic model. With fewer organisms to draw carbon from the surface and carry it to the deep sea, the ocean lost much of its ability to absorb additional CO₂.

“In all cases, much more CO₂ will remain in the atmosphere if all marine life were removed,” Tjiputra explained. “Without living organisms consuming carbon at the ocean surface, the carbon content at the ocean surface is much higher. This limits the ocean’s ability to absorb more CO₂.”

Interestingly, the simulation also showed that terrestrial ecosystems—like forests and grasslands—absorbed about half of the excess carbon the ocean couldn’t take in.

“But the simulation showed that in a scenario where all marine life is eradicated, land ecosystems will absorb about half of the carbon that the ocean cannot take up,” noted Couespel. Still, this wasn’t enough to fully offset the loss of marine carbon cycling.

The researchers stress that this is a theoretical, worst-case scenario. But by exploring the extreme, they uncovered a deeper truth: marine life is essential to climate regulation, and its loss would significantly weaken one of Earth’s most powerful carbon sinks.

The implication is clear: preserving marine ecosystems isn’t just about biodiversity—it’s about climate stability and human existence.

“A healthy ocean buys us time,” said Tjiputra. “Damage to marine ecosystems can significantly accelerate human-caused climate change and further challenge our ability to meet the goals in the Paris Agreement. Preserving the function of marine ecosystems is essential for mitigating climate change and its associated risks.”

The ocean’s biology isn’t just beautiful—it’s functional. It’s part of the planet’s climate machinery.

Whether you’re driven by conservation or commonsense risk management, a thriving ocean ecosystem is in everyone’s interest. Safeguarding it is not a partisan issue—it’s a practical investment in our future, our economy, and our shared home.

From plankton to whales, marine organisms are quietly keeping Earth cooler. If we lose them, we lose time—and possibly our shot at a livable future.

JF Tjiputra et al. Marine ecosystem role in setting up preindustrial and future climate. Nature Communications (2025). https://doi.org/10.1038/s41467-025-57371-y