Great Whales Crucial to Deep-Sea Carbon Sequestration, Research Confirms

Emerging scientific findings continue to solidify the indispensable function of great whales in the planet's natural climate regulatory systems. These massive marine mammals operate as potent biological carbon sinks, exerting a measurable influence on atmospheric carbon dioxide concentrations through their life cycles and ecological interactions. A single great whale is estimated to sequester approximately 33 tons of carbon dioxide over its existence, a figure that significantly surpasses the sequestration capacity of many terrestrial counterparts, such as a live oak tree which captures roughly 12 tons over a 500-year lifespan.

The process of long-term carbon storage is dramatically realized upon the whale's natural demise, a phenomenon termed 'whale fall.' When these colossal animals pass away, their carbon-rich carcasses descend to the abyssal plains, effectively locking away the sequestered carbon within deep-sea sediments for centuries, potentially millennia. This mechanism prevents the stored carbon from re-entering the atmosphere as carbon dioxide, a critical service for climate mitigation.

Beyond direct biomass storage, whales actively enhance the ocean's capacity to absorb atmospheric carbon through the 'whale pump' mechanism. Marine biologists, including Professor Heidi Pearson of the University of Alaska Southeast, have extensively documented this process. The whale pump involves whales feeding in nutrient-rich deep waters and subsequently defecating closer to the surface, releasing buoyant plumes of feces laden with essential nutrients like iron and nitrogen. These nutrient-rich excretions act as a fertilizer for surface phytoplankton, the microscopic marine algae responsible for photosynthesis. Phytoplankton, fueled by this nutrient upwelling, absorb vast quantities of atmospheric carbon dioxide, with global phytoplankton populations accounting for approximately 40% of the carbon captured from the atmosphere.

Research exploring baleen whales in the Southern Hemisphere indicates that at their pre-exploitation abundance, five species could have sequestered 4.0 × 10⁵ tonnes of carbon per year (tC yr−1). This sequestration capacity dropped to an estimated 0.6 × 10⁵ tC yr−1 by 1972 following extensive commercial whaling operations. Consequently, restoring whale populations is increasingly viewed as a crucial, nature-based strategy to augment the planet's inherent carbon storage capabilities.

Studies suggest that the current sequestration capacity of whales is severely limited due to historical overharvesting, creating a sequestration deficit estimated between 41.9 × 10⁶ tC and 45.2 × 10⁶ tC by 2100, depending on climate scenarios. Professor Pearson's recent work in 2023 has focused on modeling how the recovery of these populations could bolster CO2 storage, emphasizing that robust conservation and management interventions directly promoting population increases are necessary to realize this long-term, self-sustained enhancement of the ocean carbon sink. This research underscores the profound, yet often overlooked, interconnectedness between the health of marine ecosystems and the stability of the global climate framework.