Whales act as carbon sinks

Whales are so massive, that they can act as a way of storing atmospheric carbon
19 December 2022

Interview with 

Heidi Pearson, University of Alaska Fairbanks


A humpback whale and its calf


The extent of oceanographic data is not just for measures of physical changes to our planet’s hydrologic systems, it also plays a key part in ecology and conservation. Indeed a study out just this week showed that whales, which not only play a pivotal role in keeping ecosystems healthy, might also be so massive that they act as carbon sinks as well. Heidi Pearson, of the University of Alaska Fairbanks,spoke  about how oceanographic data is vital to continued studies on ocean health, and how much of a role whales might play in carbon storage.

Heidi - There are many ways that understanding the basic oceanography helps in conservation. And one big part of biological oceanography is this thing called the biological carbon pump, which describes how carbon gets from the surface layers of the ocean down to ocean depths. And with some of the research that my team has been doing, we're looking at how whales might play a role in the biological carbon pump.

Will - What kind of oceanographic data needed to be collected in order for this study to work?

Heidi - We need information on whale population sizes and whale mortality rates, body size, and then we need information on oceanic food webs, and photosynthetic rates, and nutrient levels in the water. The depth of what we call the thermocline, the temperature gradient in the water. So this type of work really pulls together many aspects of ocean science all tied to whales.

Will - And so what are some of the ways that whales can act as carbon sinks?

Heidi - Well, there's two main pathways that my team describes in our paper, and we separate them into what are called direct pathways and indirect pathways. So these direct pathways are what I just mentioned. So whales are very big. They live for a long time. And just like you and me, they're made of carbon. And so this means that they can store a lot of carbon for a long period of time. They can take it out of the atmosphere just by living their daily lives. And then when they die, these very big carcasses, most of them will sink to the sea floor. And we believe that most of them will sink to the deep sea. And sinking to the deep sea is really important in terms of carbon sinks because once something that is made of carbon like whales sink to the deep seafloor, that carbon will be trapped from the atmosphere for thousands of years, maybe even longer. And so that's really the exciting part about understanding this carbon sink. So these direct pathways that I've just described, we have a pretty good handle on it scientifically. We're fairly confident in the numbers we're getting, but in the scheme of things, it's a pretty small contribution if you think of the overall global carbon budget. So the other pathway is this indirect pathway, and this is where whales essentially release byproducts. So poop, urine, slough skin, placentas in the case of breeding females. And these byproducts are rich in nutrients. And this is important because the upper parts of the ocean are oftentimes devoid of nutrients. And nutrients are important because that's what phytoplankton take up. And phytoplankton, you can think of like tiny marine plants, they are sucking up CO2 from the atmosphere. And so when we have more nutrients in the surface, waters deposited by whales, we have the potential to stimulate phytoplankton growth and thus more capture of carbon from the atmosphere. So that indirect pathway is a lot more intricate than those direct pathways. We have less scientific understanding of that, but we believe that there is more potential for carbon capture through that indirect pathway than the direct pathway.

Will - And if the ways that these whales can be carbon sinks are so far reaching, both primary and secondary, it sounds like a very difficult task of quantifying how much effect they have in terms of being a carbon sink. And indeed is there a risk potentially of overselling their level of carbon capture?

Heidi - Yes, there is. And that was one of the driving factors for this paper. So as I mentioned, we have pretty high scientific confidence in some of these pathways fairly low at the moment in these other pathways. And the risk is overselling the carbon benefit of whales. We just don't have the data we need to fully put a carbon value on all of the ways that whales might be helping to capture, store and sequester carbon. And the risk is putting a value on whales, the carbon carbon values. And then once we get the scientific data, we find out that it doesn't quite support it. And there have been some pretty high dollar economic figures put on the carbon values of whales that our team was concerned about. And so we were attempting to rein in the science on this and our paper. We do put forth an economic framework that can be populated once we do get the requisite data in hand. But right now we don't feel like we are at a place scientifically to put an economic figure on the carbon value of whales.

Will - But you would still be confident in saying that even if their level of carbon capture is not significant enough to warrant this kind of investment, it's still an extra reason as to why they should be conserved?

Heidi - It is, absolutely. So we know that whales make some contribution to carbon dioxide removal. What we don't know right now is the full scale. And another thing we're trying to do with this work is put what we call a confident lower bound on the ability of whales to remove carbon dioxide, saying, okay, they at least do this much. We think they have this potential, but we need more data to get there. We also advocate for the precautionary principles. So there's really no downside to conserving whales. It's a low regret, low risk strategy for conserving ecosystems as a whole. So we know that whales can help to keep ecosystems healthy. We know that they can help to combat the biodiversity crisis, which we are also in. And we also know they have these climate benefits. And so if we conserve whales, we know that there's a lot of ecosystem benefits that will occur.

Will - So it strongly advocates more oceanographic data to be collected.

Heidi - Yes, absolutely. And we have a great team. We've outlined some of the outstanding questions. We've outlined some research pathways, so I think we know how to get there. We just need a little bit more time and resources to answer all of these critical questions.


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