However, historical whaling has made whale populations plummet. Overseas researchers have modelled five species of southern whales to find that they could sequester 400,000 tonnes of carbon a year before the onset of commercial whaling.

However by 1972, whales were storing only 15% of what they did before whaling. By 2100, these slowly recovering whale populations will only sequester carbon at around less than half of their pre-whaling levels under a “business as usual” climate change scenario.

Despite the importance of marine megafauna on ecosystem functioning, their contribution to the oceanic carbon cycle is still poorly known.

In new research, we explored the role of baleen whales in the biological carbon pump across the Southern Ocean. We accounted for both past exploitation and future impacts of climate change on whales' recovery. We modelled whale-mediated carbon sequestration through the sinking of carcasses after natural death. We reveal that whales could sequester 4.0x10^5 tonnes of carbon per year before exploitation, but that whaling has drastically reduced their sequestration potential.

Now whale populations and the associated carbon pump is imperiled by climate change, with predicted carbon sequestration in 2100 being less that half of its historical value.