Whale of a tale? Stories about whales helping to tackle climate change are exaggerated

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Whales have long fascinated us with their size and beauty. Once we stopped whaling, their populations started to recover, in a major conservation victory.

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Research has suggested that healthy whale populations could help us in unexpected ways by storing carbon in the long term.

As? Whales are usually huge. Among them is the blue whale, the largest animal that ever lived. With a length of up to 30 meters and 190 tons, they are larger than any dinosaur. This gives these mega-mammals an oversized role in the oceans. Their plumes of poop contain so many nutrients that phytoplankton blooms can form in its wake. These tiny photosynthetic creatures absorb carbon dioxide in their bodies. When they die, they can sink to the bottom and be covered in sediment, storing the carbon.

As we desperately seek good climate news amid the accelerating crisis, the whales seemed to be offering one. Bring back whales, store more carbon naturally.

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But this is premature, as our new research points out. This area is full of uncertainty and lack of data. While the story sounds good, we simply can’t say that more whales mean more carbon storage at this point. If we focus on unproven measures like boosting whale populations, we risk diverting attention away from proven climate measures like steadily reducing emissions from burning fossil fuels or protecting our blue carbon stores in mangroves and grasslands. of seaweed.

Whale poop floating on the surface in Antarctica.

Why has there been so much attention on whales?

The climate crisis is intensifying. Our first year of over 1.5 warming could come within five years. That said, governments and researchers are looking for ways to address this global crisis by using nature to extract CO2 from the air.

Trees and peat bogs are natural carbon sinks. So is the blue carbon stored in mangroves and kelp meadows for thousands of years.

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So why not whales? In recent years, there has been growing enthusiasm for whales, any marine animal capable of boosting phytoplankton growth is likely adding to nature’s ways of storing carbon.

Here’s how the chain of events would work. As whales feed and migrate, they pump large amounts of nutrients between different parts of the oceans and different depths mostly through their poop. They also act as a conveyor belt, carrying nutrients between different oceans. One species, the gray whale, is the largest animal involved in bioturbation, which means they churn up sediment as they burrow into the seabed in search of shrimp.

These roles make whales ecosystem engineers. Their activities are significant enough to shape local ecosystems where they feed and fertilize the ocean surface through defecation. Whale poop, in particular, appears to have a significant effect on phytoplankton growth, especially in the Southern Ocean.

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sperm whale poop
A pooping whale is a real occurrence, as this sperm whale shows. But is it enough to make a difference at an ecosystem level?
Shutterstock

Fish and other marine species also contribute to the biological carbon pump. In this process, CO is stored in organic matter through photosynthesis and washed into the deeper ocean where some is stored for long periods of time.

Whales could also potentially capture carbon in other ways: in their meat, where they store it throughout their long lives, and when a whale falls and sinks to the bottom, where it could be covered in sediment.

These are the five main pathways by which whales could contribute to carbon sequestration.

So why should we be sceptical?

While its entirely possible whales could help sequester carbon, they are likely to make only a limited contribution.

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Research in this area is challenging, with many complexities and uncertainties. How do you measure the contribution to a whale’s life? We’ll need more research to find out either way.

For now, what we know suggests that the blue carbon in mangroves, salt marshes and algae is far beyond what large whales contribute to carbon storage.

To make a conclusive statement that whales may play a role in reducing atmospheric CO concentration, we should be able to draw a clear link between how they affect the biological carbon pump, with more whales leading to more organic carbon directed from the surface to the interior. the deep ocean and how much of it is then stored long-term in sediments.

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Whales are big. But we don’t know enough about them to say they’re good at storing carbon. This image shows a humpback whale feeding in Antarctic waters.
Lauren Harrell

What we know about how oceans respond to carbon dioxide adds further weight to whale skepticism. Of the carbon dioxide we emitted between 2009 and 2018, about 40% remained in the atmosphere, 29% was absorbed by terrestrial ecosystems and 23% was absorbed by the oceans, largely due to tireless photosynthesis of phytoplankton. The cold Southern Ocean is the major contributor among the oceans, accounting for 40% of all ocean uptake.

Scaled down, all of the world’s oceans absorb about 53 billion tons of carbon a year. Of this, 4 billion tons of organic matter sink below the surface. But only 1% of that is actually stored in long-term seafloor sediments.



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Read more: Bottoms up: How whale poop helps feed the ocean


So when we look at five ways whales could boost carbon removal, the most important is through their massive feces, which can trigger plankton growth. The whale pump is also powered by their poop, and when gray whales or other species spill sediment, it has only a local effect. When a dead whale falls to the seabed and is eaten, some of the carbon can be stored long-term if its bones are buried. But that’s unlikely to be a significant amount.

In short, we don’t know enough to say that whales help with carbon storage, and what we do know suggests otherwise.

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Whales are more than their carbon

Whales are valuable for much more than just their role in carbon cycles. They are celebrated in cultures around the world. They support local economies through industries such as whale watching. Whales host many other species on them, provide a vital food source for deep-sea life when they die, and serve as an indicator of ocean health.

Whale watching in Australia.

And while some species hard hit by whaling are now recovering, many whales face a very uncertain future in a rapidly warming ocean.

Whales are unlikely to protect us from climate change. It is more likely that we will have to save them.

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Read more: Could sea creatures store carbon in the ocean protect them and help slow climate change?


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