Whales play an essential role in marine ecosystems and in the carbon cycle, but we probably shouldn’t go counting on them to be able to do anything to reverse climate change for us
Whales devour huge amounts of carbon-rich food and act as living carbon stores. At the same time, they fertilise carbon dioxide-consuming phytoplankton. And when a whale finally dies, its carcass typically ends up on the ocean floor, where it gets covered by sediment that prevents the carbon it stored up during its life from reaching the atmosphere.
Studies have suggested this could mean that whales could actually be helping to slow the pace of climate change. But, as a recent study that takes a close look at the carbon cycle and the contribution of whales, shows, it turns out this isn’t the case after all. The research team, led by Griffith University in Australia, studied the main mechanisms by which baleen whales such as humpback and fin whales remove carbon from the atmosphere and found that their potential carbon sequestration is not sufficient to alter the course of climate change significantly.
“Our study supports that whales are important for the marine ecosystem, but their contribution to the global carbon flux is too small to effectively reduce atmospheric carbon,” Olaf Meynecke, a marine scientist with Griffith University and lead author of the paper, said in a news release.
Even though promoting whales as carbon sinks could aide conservation efforts, perpetuating it would be misleading, he felt. Indeed, Dr Meynecke fears that giving whales a role in addressing climate change creates false hope in their ability to fix things for us, and “may act to further delay the urgent behavioural change needed to avert catastrophic climate change impacts”. Such a delay could, indirectly at least, harm the recovery of whale populations, he reckons.
But that’s exactly what’s still happening: in a non-representative internet search for the keywords “whales” and “carbon”, the research team found that, between 2012 and 2022, 352 news articles in more than 45 countries had been published about the topic, with a “strong increase” in the past three years. In contrast, only six scientific papers about the subject were published during the same period, underscoring the gap between available scientific evidence and media response, the paper argues. Social media, it said, further amplifies this phenomenon.
While whales are vital to the healthy functioning of marine ecosystems, Dr Meynecke worries that overstating their ability to prevent or counterbalance human-induced changes in global carbon budgets may unintentionally redirect attention from well-established methods of reducing greenhouse gases.
Previous estimates, he said, neglect the scale at which carbon sequestration occurred both temporally and spatially. This is particularly true of whale falls (when whales die and their carcass sinks to the ocean floor where the carbon is retained for decades). “Some of the pathways suggested for carbon sequestration such as whale falls also underestimate the breathing of whales.”
Instead of focusing solely on whales, the authors say we should advance the protection of marine ecosystems in general. Mangroves, salt marshes, seagrass beds and the deep sea are particularly good at removing carbon from the atmosphere. “Large-scale protection of marine environments including the habitats of whales will build resilience and assist with natural carbon capture,” the study says.
The ocean carbon cycle plays an important role in regulating the global climate: between 20% and 32% of carbon dioxide stemming from human activity enters the oceans from the atmosphere through various processes, and about 40% of this is absorbed by the Southern Ocean alone. We can count on whales to capture some of that for us, just not enough to save us from ourselves.
Julia Hager, PolarJournal
Jan-Olaf Meynecke, Saumik Samanta, Jasper de Bie et al. Do whales really increase the oceanic removal of atmospheric carbon? Frontiers in Marine Science, 2023; 10 DOI: 10.3389/fmars.2023.1117409
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