Whales’ bodies are enormous stores of carbon. They sink to the ocean floor when they die, and the carbon stored in their enormous bodies is transferred from surface waters to the deep sea, remaining there for centuries or more. But if a whale is killed and processed, that carbon is released into the atmosphere. Whales feed in the deep ocean, then return to the surface to breathe and poo. Their iron-rich faeces creates perfect growing conditions for phytoplankton that capture an estimated 40% of all CO2 produced. As whale populations declined, the orcas that predated them turned to smaller marine mammals like sea otters that subsequently declined, leading to the spread of sea urchins that destroy the kelp forests around the North Atlantic, with a knock-on effect on marine carbon sequestration. The good news is that there is now an attempt to increase protection for whales based on their climate change relevance.
www.bbc.com/future/article/20210119-why-saving-whales-can-help-fight-climate-change