The world's largest animals are unusually good at taking carbon dioxide out of the atmosphere.
Whales are among the largest creatures on Earth. Their bodies are enormous stores of carbon, and their presence in the ocean shapes the ecosystems around them.
From the depths of the ocean, these creatures are also helping to determine the temperature of the planet – and it's something that we've only recently started to appreciate. "On land, humans directly influence the carbon stored in terrestrial ecosystems through logging and the burning of forests and grasslands," according to a scientific paper. "In the open ocean, the carbon cycle is assumed to be free of direct human influences."
But that assumption neglects the surprising impact of whaling. Humans have killed whales for centuries, their bodies providing us with everything from meat to oil to whalebone. The earliest record of commercial whaling was in 1000 CE. Since then, tens of millions of whales have been killed, and experts believe that populations may have declined from anywhere between 66% and 90%.
When whales die, they sink to the ocean floor – and all the carbon that is stored in their enormous bodies is transferred from surface waters to the deep sea, where it remains for centuries or more.
In the study, scientists found that 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 – that's the equivalent of taking between 40,000 and 410,000 cars off the road each year. But when the carcass is prevented from sinking to the seabed – instead, the whale is killed and processed – that carbon is released into the atmosphere.
Andrew Pershing, a marine scientist at the University of Maine and an author of that study, estimates that over the course of the 20th Century whaling added about 70 million tonnes of carbon dioxide into the atmosphere. "This is a lot, but 15 million cars do this in a single year. The US currently has 236 million cars," he says.
But whales are not only valuable in death. The tides of excrement that these mammals produce are also surprisingly relevant to the climate.
Whales feed in the deep ocean, then return to the surface to breathe and poo. Their iron-rich faeces creates the perfect growing conditions for phytoplankton. These creatures may be microscopic, but, taken together, phytoplankton have an enormous influence on the planet's atmosphere, capturing an estimated 40 percent of all CO2 produced – four times the amount captured by the Amazon rainforest.
Restoring whale populations to their pre-whaling numbers could be an important tool in tackling climate change, sequestering carbon both directly and indirectly, and thus helping to make a small dent in the enormous volume of CO2 emitted by fossil fuels every year.
And, unlike with risky geoengineering techniques, the benefits would not just accrue to the climate, but to the whole ecosystem.
In 2019, the International Monetary Fund published a report looking at the benefits of putting whales back in the ocean. And they did it in a way that politicians would understand: by putting a dollar value on it.
This study found that, 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 $2m (£1.48m), with the entire global stock amounting to over $1tn (£740bn).
The IMF study concludes that whale protection must now become a top priority in the global effort to tackle climate change. "Since the role of whales is irreplaceable in mitigating and building resilience to climate change, their survival should be integrated into the objectives of the 190 countries that in 2015 signed the Paris Agreement for combating climate risk," the authors write.
Later this year, the UN climate conference will take place in Scotland, a country whose coasts regularly host species like minke and humpback whales. With a carbon market for whales now a real possibility, perhaps it's time to put these creatures on the agenda.
It would be lovely to think that an orchestra playing music on an ocean raft would attract whales. However, this gorgeous, inspirational video was actually created by some clever ad men at M&C Saatchi in Australia for a telecomms client.