Blue carbon: the climate role of whales

What if whales were allies of the climate? By feeding at depth and then fertilising the surface with their faeces, they boost the phytoplankton, which captures CO₂ and produces half the planet’s oxygen. This is the “whale pump“, at the heart of the concept of blue carbon.

The widget above presents the mechanisms (the whale pump, whale falls, vertical mixing) and the key figures. An IMF report estimates that a single great whale sequesters about 33 tonnes of CO₂ over its lifetime: restoring the populations would amount to rebuilding a natural carbon sink.

Blue carbon, carbon sinks and ecosystem services

Blue carbon is the name given to the carbon captured and stored by marine and coastal ecosystems (seagrass beds, mangroves, but also large animals). Whales contribute to it in two ways: by fertilising the surface phytoplankton (the whale pump) and by sequestering carbon in their own bodies, which end up on the seabed in a whale fall.

This carbon sink function comes on top of the other services cetaceans provide: structuring food webs, dispersing nutrients such as iron and nitrogen, supporting the productivity of fisheries. It is the central argument for treating whale conservation as a genuine climate lever.

Further reading: see whale falls, the great migrations and the diets that feed this pump.