The Earth’s great whales are magnificent, intelligent, and peaceful. But new research shows that they also help keep the planet cool—in life, and in death. Such knowledge has put a new urgency to the call to “save the whales,” as doing so may also help cool the climate. 

Blue, baleen, and sperm whales are massive creatures, which means the tissue in their bodies stores an enormous amount of carbon, reports the BBC’s Future Planet. And when a whale dies a natural death, its body sinks slowly to the ocean floor, thereby transferring that huge carbon store “to the deep sea, where it remains for centuries or more.”

If, however, the whale is killed and its carcass does not sink, the carbon eventually slips away into the atmosphere. 

“Before industrial whaling, populations of whales (excluding sperm whales) would have sunk between 190,000 to 1.9 million tonnes of carbon per year to the bottom of the ocean,” writes the BBC, citing a 2010 study published by PLOS ONE. 

“That’s the equivalent of taking between 40,000 and 410,000 cars off the road each year.”

Study co-author Andrew Pershing, a marine scientist with the University of Maine, estimated that 20th-century whaling likely added around 70 million tonnes of CO2 to the atmosphere. “This is a lot, but 15 million cars do this in a single year. The U.S. currently has 236 million cars,” he noted.

But more recent research has revealed that a living whale is also an extraordinary boon to the climate. Or rather, more strictly speaking, the boon lies in its prodigious poops. 

While it is common knowledge that whales come to the surface to breathe, it is less well known that they also do so to defecate, and that their iron-rich feces in turn creates “the perfect growing conditions for phytoplankton,” writes BBC.

And it is upon these microscopic creatures that the fate of our climate may largely depend, as they sequester “an estimated 40% of all CO2 produced—four times the amount captured by the Amazon rainforest.” 

By providing them with an environment to grow, whales create a “multiplying effect on phytoplankton productivity and the ocean’s ability to absorb carbon,” said Vicki James, policy manager at Whale and Dolphin Conservation (WDC). “We need to think of whaling as being a tragedy that has removed a huge organic carbon pump from the ocean.” 

James told the BBC that whale carcasses also “provide a unique habitat for deep sea species, many of which are only found on these ‘whale falls’.” In its final stage of decay, the remains of a  single whale can provide food and habitat for up to 200 species.  

In a 2019 report, the International Monetary Fund called the carbon capture potential of whales “truly startling.” Each time a great whale dies a natural death and slips down the water column to the ocean floor, it ends up sequestering—for centuries—about 33 tonnes of carbon. “A tree, meanwhile, absorbs only up to about 48 pounds of CO2 a year,” IMF writes. 

As for the whale poop-phytoplankton continuum, the IMF notes that “if whales were allowed to return to their pre-whaling number of four to five million—from slightly more than 1.3 million today—it could add significantly to the amount of phytoplankton in the oceans and to the carbon they capture each year.”

If whale activity could create even a tiny boost to phytoplankton productivity—just a 1% increase, writes IMF—that could “capture hundreds of millions of tonnes of additional CO2 a year, equivalent to the sudden appearance of two billion mature trees.”

While the IMF notes that saving the whales is an uphill battle—calling them a classic example of the “tragedy of the commons,” in which “no individual who benefits from them is sufficiently motivated to pay their fair share to support them”—it does suggest actions that could make difference. Top of the list: a whale carbon market. 

“When you add up the value of the carbon sequestered by a whale during its lifetime, alongside other benefits like better fisheries and ecotourism, the average great whale is worth more than US$2 million, with the entire global stock amounting to over $1 trillion,” explains BBC.