Why supporting whales can help combat climate change.

One of the planet’s greatest carbon sinks, the ocean absorbs nearly a third of greenhouse gas emissions from the atmosphere.

The great whales, a population that can have a significant impact on the ecosystem around them due to their sheer size, are found swimming in its depths. Although scientists have known for some time that whales play an important role in the carbon cycle of the ocean, it has been difficult to quantify exactly how these animals affect the seas and what we lost when they were killed off a century ago.

That challenge has now been accepted by a group of scientists. One of the most comprehensive studies to date on the amount of carbon that great whales absorb from the ocean and its significance in the fight against climate change was recently published by a group of ecologists, biologists, and oceanographers.

According to the lead researcher of the study, marine biologist Heidi Pearson of the University of Alaska Southeast, “large-bodied animals, they live for a long time, and many of them migrate over vast distances.” As a result, they may have significant effects on the ecosystem, including the carbon cycle.

The bodies of whales contain an enormous amount of carbon that would otherwise be present in the ocean or atmosphere, where they have the greatest impact.

The authors discovered that twelve species of great whales, including minkes, Antarctic minkes, sei, Bryde’s, blue, fin, bowhead, gray, humpback, and three right whale species, contain an estimated 2 million metric tons of carbon in their bodies. That’s about the same as the carbon dioxide produced when 225 million gallons of gasoline are burned.

And that only includes the cetacean family’s living members. Whale falls, the bodies of dead whales that sink to the seafloor and support an ecosystem of scavengers, trap an additional 62,000 metric tons of carbon each year, which is the equivalent of 7 million gallons of gas.

“Whale falls are a very good way, in terms of efficiency, of taking carbon from the upper ocean and putting it in the deep sea for sequestration,” said Craig Smith, an oceanographer at University of Hawaii at Manoa who worked on the study.

A lifetime’s worth of carbon is lost when a whale dies in open water and sinks into the deep. Since it can take up to 1,000 years for the elements and water at the bottom of the sea to return to the surface, carbon is effectively stored for more than a millennium.

Additionally, a less majestic but crucial byproduct, whales indirectly influence the ocean’s carbon cycle: their feaces.

The nutrients nitrogen, phosphorus, and iron found in whale feaces are essential for phytoplankton growth. Ocean surface waters contain relatively little of these nutrients.

However, when whales urinate close to the surface of the ocean, their waste boosts the growth of carbon-consuming organisms throughout the ecosystem by fertilising those at the base of the marine food chain. According to the study’s authors, this process is responsible for fixing an estimated 22 million metric tons of carbon in a network of living animals in the Southern Ocean alone.

The study was published in Trends in Ecology and Evolution in December.

Michael J. Moore, a senior scientist and veterinarian at the Woods Hole Oceanographic Institution who was not involved in the work, said that the paper is The paper is “an excellent synthesis of the progress that has been made in the past decade” on quantifying the role that whales play in the carbon cycle.

It’s “a wonderful thought experiment with oceans of unknowns,” he said, many of which the authors acknowledge in the paper.

Firstly, according to Pearson, the researchers were unable to quantify the amount of carbon that whales breathe back into the atmosphere through respiration.

The effect of whale waste in particular is difficult to quantify because whales are a population that is literally difficult to measure. However, their collective research reveals that the ocean is healthier the more whales there are.

“Whale recovery,” the study authors conclude, “could be an effective ‘low-regret’ CDR [carbon dioxide removal] strategy with less risk, longer permanency and higher efficiency than geoengineering solutions.”

The devastating effects of industrial whaling on whale populations have not yet subsided. According to the authors, commercial hunting in the 19th and 20th centuries resulted in the release of 17 million metric tons of carbon that had been previously stored in the bodies of baleen whales into the atmosphere and reduced the total mass of whales on the planet by 81 percent.

The seas can’t be healed just by rebuilding whale populations on their own. The highest amount of carbon dioxide ever recorded in a single year was released by fossil fuel use worldwide in 2022, when it reached 37.5 billion metric tons. That’s more than 18,000 times more carbon than all of the great whales that are currently alive.

Whales alone “are not going to solve climate change, but thinking about whales as playing a role in the carbon cycle can help motivate conservation,” said Andrew Pershing, a co-author of the study and director of climate science at the nonprofit Climate Central. “There are a lot of win-wins there, and I think that’s very true of a lot of natural climate solutions.”

 

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