Whales in the carbon cycle: can recovery remove carbon dioxide?

• Published in: Trends in ecology & evolution (Amsterdam) Vol. 38; no. 3; pp. 238 - 249
• Main Authors: Pearson, Heidi C., Savoca, Matthew S., Costa, Daniel P., Lomas, Michael W., Molina, Renato, Pershing, Andrew J., Smith, Craig R., Villaseñor-Derbez, Juan Carlos, Wing, Stephen R., Roman, Joe
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2023
• Subjects: Animals; biological carbon pump; Biomass; blue carbon; Carbon Cycle; Carbon Dioxide - metabolism; carbon sequestration; climate change; Ecosystem; great whale; nature-based solution; Whales; great whale; nature-based solution; blue carbon; biological carbon pump; carbon sequestration; climate change
• ISSN: 0169-5347; 1872-8383; 1872-8383
• DOI: 10.1016/j.tree.2022.10.012

The great whales (baleen and sperm whales), through their massive size and wide distribution, influence ecosystem and carbon dynamics. Whales directly store carbon in their biomass and contribute to carbon export through sinking carcasses. Whale excreta may stimulate phytoplankton growth and capture atmospheric CO2; such indirect pathways represent the greatest potential for whale-carbon sequestration but are poorly understood. We quantify the carbon values of whales while recognizing the numerous ecosystem, cultural, and moral motivations to protect them. We also propose a framework to quantify the economic value of whale carbon as populations change over time. Finally, we suggest research to address key unknowns (e.g., bioavailability of whale-derived nutrients to phytoplankton, species- and region-specific variability in whale carbon contributions). As climate change accelerates, there is increasing interest in the ability of whales to trap carbon (i.e., whale carbon), yet it is currently undetermined if and how whale carbon should be used in climate-change mitigation strategies.Restoring whale populations will enhance carbon storage in whale biomass and sequestration in the deep sea via whale falls, though the global impact will be relatively small.Whale-stimulated primary productivity via nutrient provisioning may sequester substantially more carbon, though there is uncertainty regarding the carbon fate in these food webs.Recovery of whale populations via reduction of anthropogenic impacts can aid in carbon dioxide removal but its inclusion in climate policy needs to be grounded in the best available science and considered in tandem with other strategies known to directly reduce greenhouse gas emissions.