The Role of Whales in the Carbon Cycle

To combat climate change, nature-based solutions take a holistic approach, promoting ecosystem preservation and biodiversity. Although several efforts have concentrated on restoring wetlands or planting trees, scientists emphasize the importance of understanding the potential of carbon sequestration of whales — the largest animal on the planet.

The study was published on December 15^th, 2022, in Trends in Ecology and Evolution on December. In this study, the researchers analyze how these marine giants can impact the amount of carbon in the water and air and possibly contribute to the total reduction of atmospheric carbon dioxide.

“Understanding the role of whales in the carbon cycle is a dynamic and emerging field that may benefit both marine conservation and climate-change strategies. This will require interdisciplinary collaboration between marine ecologists, oceanographers, biogeochemists, carbon-cycle modelers, and economists,” say the authors, headed by Heidi Pearson, a biologist from the University of Alaska Southeast.

Whales can live for more than 100 years, weigh up to 150 tons, and be the size of large airplanes. Their bulky biomass consists largely of carbon, like all living things, and they comprise one of the major living carbon pools in the pelagic ocean, which is a part of the marine system that is accountable for storing 22% of the total carbon of the Earth.

The authors state, “Their size and longevity allow whales to exert strong effects on the carbon cycle by storing carbon more effectively than small animals, ingesting extreme quantities of prey, and producing large volumes of waste products. Considering that baleen whales have some of the longest migrations on the planet, they potentially influence nutrient dynamics and carbon cycling over ocean-basin scales.”

Every day, whales consume a maximum of 4% of their hefty body weight in photosynthetic plankton and krill. This equates to around 8,000 pounds in the blue whale. Once they complete their food digestion, their excretion is rich in essential nutrients that aid in the flourishing of these krill and plankton, helping in enhanced photosynthesis and carbon storage from the atmosphere.

A blue whale can survive for a maximum of 90 years. Once they die, their bodies fall to the seafloor; and as they decay, the carbon they comprised is transported to the deep sea. This supplements the biological carbon pump, where chemicals and nutrients are transferred between the atmosphere and the ocean via complicated biogeochemical pathways. Commercial hunting, which is the biggest reason for population decline, has reduced whale populations by 81%, with unidentified impacts on biological carbon pumps.

“Whale recovery has the potential for long-term self-sustained enhancement of the ocean carbon sink. The full carbon dioxide reduction role of great whales (and other organisms) will only be realized through robust conservation and management interventions that directly promote population increases,” authors conclude.

Journal Reference:

Pearson, H., C., et al. (2022) Whales in the Carbon Cycle: Can Recovery Remove Carbon Dioxide? Trends in Ecology & Evolution. doi.org/10.1016/j.tree.2022.10.012.