“Understanding the role of whales in the carbon cycle is a dynamic and emerging field that can benefit both marine conservation and climate change strategies,” wrote the authors, led by biologist Heidi Pearson. University of Alaska Southeast.
The ocean is by far the largest carbon sink in the world, having absorbed around 40% of all carbon dioxide emitted by the burning of fossil fuels since the industrial revolution.
Marine biologists have recently discovered that whales, especially large whales, also play an important role in capturing carbon from the atmosphere. They can weigh up to 28 tonnes and live for more than 100 years, the researchers wrote, and their size and long lifespan mean they store more carbon in their bodies than other small animals. When they die, they sink to the bottom of the ocean, removing carbon from the atmosphere for centuries.
“Whales consume up to 4% of their massive body weight in krill and photosynthetic plankton each day. For the blue whale, this equates to nearly 8,000 pounds,” the scientists wrote. digest their food, their droppings are rich in important nutrients that help these krill and plankton thrive, contributing to increased photosynthesis and storing carbon from the atmosphere.”
A report 2019 published by the International Monetary Fund estimated that a large whale sequesters 33 tonnes of carbon dioxide each year on average, while a tree only absorbs up to 48 pounds per year – a figure the report’s authors have used to suggest that conservationists are better off saving whales than planting trees.
The new paper explores how a restoration of whale populations to pre-hunting levels – between 4 million and 5 million, up from just over 1.3 million in 2019, according to the IMF report – could increase the animals’ ability to act as a carbon sink. (Commercial whaling, the main reason why whale numbers have declined, has reduced their populations by 81%, the researchers said.)
Among a number of whale species, the amount of carbon that was sequestered “jumps an order or two of magnitude” with a recovery in the whale population, said Stephen Wing, co-author of the paper and marine science teacher. at the University of Otago in New Zealand.
The figures are “relatively small” given the scale of the global climate challenge, “but compared to the pledges some countries are making to reduce CO2 emissions, they are relatively large”, he added.
“We’re sort of doing a backcast and saying the recovery could be up to pre-hunting numbers because the system has already supported that number of whales,” Wing said.
Whales, along with a number of marine animals, are vulnerable to climate change as rising temperatures push them into new habitats. They rank among the most endangered marine mammalsincluding the North Atlantic right whale, only about 340 left.
Whales are always killed in surprisingly high numbers, years after commercial whaling was banned, in waters brimming with ships battering them and ropes tangling them. Offshore wind turbines — part of President Biden’s Clean Energy Agenda — are also set to encroach on their habitat as the administration tries to balance the fight against global warming with the protection of wildlife.
“Whale recovery has the potential for long-term, self-sustaining enhancement of the ocean carbon sink,” the authors wrote. “The full carbon dioxide-reducing role of great whales (and other organisms) will only be realized through robust conservation and management interventions that directly support population increases.”
However, the authors were cautious about the calculations underlying the inclusion of whale carbon in any broader climate change mitigation strategy, as there are still many scientific unknowns. They argued that recent studies valuing the carbon contribution of a single blue whale at $1.4 million “are based on assumptions beyond our understanding of whale ecology and biological oceanography. “.
Dino Grandoni and Tatiana Schlossberg contributed to this report.