The ocean has a secret.I am very lucky to work in the field of ocean health. I grew up in a coastal English village, and spent a lot of time looking at the sea, wondering at its secrets. Now I’m working to preserve them.The ocean, as we know, is critical to all oxygen-dependent life, you and me included! But life is also critical to the ocean. The ocean produces so much oxygen because of ocean plants. These plants draw down carbon dioxide (CO2), a greenhouse gas, and convert it to carbon-based sugars and oxygen. They are climate change heroes! There is now wide recognition of the role of ocean life in slowing climate change, there’s even a term: blue carbon. But there is a secret… Ocean plants can only draw down as much CO2 as they do, and oceans can only store as much carbon as they do, because of ocean animals. In April, on the Pacific island of Tonga, I had the opportunity to present this secret at the “Whales in a Changing Ocean” conference. In many Pacific Islands, whales support booming tourism economies, and are culturally important. While we are rightly concerned about the impacts of climate change on whales, we also need to recognize that whales can be a great, big ally in fighting climate change! Through their deep dives, vast migrations, long life spans, and large bodies, whales have an enormous role in this ocean secret.