Priming the whale pump
After decades of industrialised whaling, overall whale populations around the globe
are 25 per cent of what they once were. There have been movements to save the whales, as we gradually appreciate the importance of biodiversity and find admiration for the capabilities of these impressive creatures. What we are now realising is that whales may also hold a key to fighting climate change.
The potential of whales to capture carbon is impressive. Whales accumulate carbon in their bodies during their long lifetimes and play a significant role in capturing carbon from the atmosphere. A large great whale such as a humpback sequesters an average of 30 tonnes of carbon dioxide, taking that carbon out of the air for centuries. A tree by comparison, absorbs about 22kg of carbon dioxide per year. A live oak tree, one of the most efficient carbon-capturing tree species, captures about 11 tonnes in a 500-year lifetime.
As impressive as this is, carbon accumulation, or sequestration, is not the end of the story for whales. Many species of whale dive deep to hunt for nutrientrich prey. Since they are mammals, they must rise to the surface to breathe and as they do, they release large amounts of nutrient-rich faeces and urine. This is referred to as the “whale pump”, because the whales are eff ectively pumping nutrients such as phosphorus, nitrogen and iron from the ocean depths to the surface. On the surface, these nutrients feed phytoplankton and blooms of these phytoplankton capture the equivalent of four Amazon rainforests’ worth of carbon dioxide each year.
Even more, when a whale dies, their carcass often sinks to the ocean floor, trapping the carbon stored in their bodies at the great depths. These “whale falls” can capture carbon for hundreds of years. As the carcass decomposes, the carbon is sequestered in sediment and cycles through the deep-sea ecosystem preventing it returning to the atmosphere as carbon dioxide.
The scale on which whales contribute to the planet’s management of carbon is staggering. When it comes to saving the planet, one large whale is worth 1000 trees. By saving the whales, we are saving ourselves.
