Restoring whales to their pre-hunted numbers could capture 1.7 billion tonnes of CO2 a year

There’s no doubt that whales are one of the most extraordinary animals on our planet, but did you know that they’re also helping to lighten the load of climate change?

We tend to think of trees as doing the bulk of natural work to absorb CO2 from the atmosphere. While that’s certainly true on land, under the sea these titans of the ocean are playing a huge role.

Whales store large amounts of carbon in their bodies, and when they die they take it to the bottom of the ocean floor. Known as ‘whale falls’, these sinking carcasses ensure that the carbon is trapped in the deep sea rather than being released in surface waters.

New research at marine sanctuaries off San Francisco has revealed that whale falls represent roughly 60 % of annual carbon sequestration (or storage) there. This is greater than the combined efforts of ‘kelp export’ – where seaweed moves carbon loads out to the deep ocean – and the carbon-capturing habitats of seagrass and salt marsh.

The whale pump

Wherever whales, the largest living things on earth, are found, so are populations of some of the smallest, phytoplankton. These microscopic creatures not only contribute at least 50 % of all oxygen to our atmosphere, they do so by capturing about 37 billion metric tons of CO2, an estimated 40 % of all CO2 produced.

To put things in perspective, we calculate that this is equivalent to the amount of CO2 captured by 1.70 trillion trees—four Amazon forests’ worth—or 70 times the amount absorbed by all the trees in the US Redwood National and State Parks each year. More phytoplankton means more carbon capture.

In recent years, scientists have discovered that whales have a multiplier effect of increasing phytoplankton production wherever they go. How? It turns out that whales’ waste products contain exactly the substances—notably iron and nitrogen—phytoplankton need to grow.

Whales bring minerals up to the ocean surface through their vertical movement, called the “whale pump,” and through their migration across oceans, called the “whale conveyor belt.” Preliminary modeling and estimates indicate that this fertilizing activity adds significantly to phytoplankton growth in the areas whales frequent.

International public good

Whales produce climate benefits that are dispersed all over the globe. And because people’s benefits from the existence of whales do not diminish the benefits that others receive from them, they are a textbook public good.

This means that whales are affected by the classic “tragedy of the commons” that afflicts public goods: no individual who benefits from them is sufficiently motivated to pay their fair share to support them.

Just think of the importance of earth’s atmosphere to our survival. Even though all nations acknowledge that everyone has an interest in preserving this common resource for the future, global coordination remains a problem.

Letting whales live

This is where the whales come in. If whales were allowed to return to their pre-whaling number of 4 to 5 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.

At a minimum, even a 1 percent increase in phytoplankton productivity thanks to whale activity would capture hundreds of millions of tons of additional CO2 a year, equivalent to the sudden appearance of 2 billion mature trees. Imagine the impact over the average lifespan of a whale, more than 60 years.

Despite the drastic reduction in commercial whaling, whales still face significant life-threatening hazards, including ship strikes, entanglement in fishing nets, waterborne plastic waste, and noise pollution. While some species of whales are recovering—slowly—many are not.

Enhancing protection of whales from human-made dangers would deliver benefits to ourselves, the planet, and of course, the whales themselves. This “earth-tech” approach to carbon sequestration also avoids the risk of unanticipated harm from suggested untested high-tech fixes. Nature has had millions of years to perfect her whale-based carbon sink technology. All we need to do is let the whales live.

Now we turn to the economic side of the solution. Protecting whales has a cost. Mitigating the many threats to whales involves compensating those causing the threats, a group that includes countries, businesses, and individuals. Ensuring that this approach is practical involves determining whales’ monetary value.