(Bloomberg) –– Climate activists would be better off trying to save whales rather than planting trees if they had to choose between those options, according to a report published by the International Monetary Fund.

Great whales are the carbon-capture titans of the animal world, absorbing an average of 33 tons of CO2 each throughout their lives before their carcasses sink to the bottom of the ocean and remain there for centuries, according an article in the December issue of the IMF’s Finance & Development magazine. A tree, by contrast, absorbs no more than 48 pounds of the gas a year.

That difference prompted Ralph Chami and Sena Oztosun from the IMF’s Institute for Capacity Development, and two professors, Thomas Cosimano and Connel Fullenkamp, to argue that supporting international efforts to restore whale populations, decimated to 1.3 million by years of industrialized hunting, “could lead to a breakthrough in the fight against climate change.”

Read more: Why TIME Devoted an Entire Issue to Climate Change

“Coordinating the economics of whale protection must rise to the top of the global community’s climate agenda,” they wrote. “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.”

In addition to binding significant amounts of CO2 themselves, whales also support the production of phytoplankton, which contributes at least 50% of all oxygen to the Earth’s atmosphere and captures as much CO2 as 1.7 trillion trees, or four Amazon forests.

Increasing phytoplankton productivity by just 1% would have the same effect as the sudden appearance of 2 billion mature trees, according to the study.

Protecting whales and raising their numbers comes at a cost. The authors put the value of one animal at more than $2 million, taking into account the value of carbon sequestered over the whale’s lifetime as well as other economic contributions such as fishery enhancement and ecotourism.

The researchers argue that if the whale population were allowed to grow to around 4 to 5 million — the total before the era of whaling — thereby capturing 1.7 billion tons of CO2 annually, it would be worth about $13 per person per year in subsidies.

International financial institutions would be “ideally suited to advise, monitor, and coordinate” actions of individual countries, the authors said.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.