For every headline about blazing wildfires, we also need to think of ocean acidification, caused when the pH of oceans falls as they absorb the extra carbon dioxide released by burning fossil fuels. The more acidic our oceans, the more shells and bone structures dissolve. This affects everything from zooplankton to whales.
The humpback whales we encountered feed on herring and small forage fish. They eat more than 2,000 pounds of food each day. Herring compose a major portion of their consumption. And what do the herring eat? They eat small sea snails, pteropods (a type of mollusk) known as sea butterflies, which have a winged foot held in place by a small, internal shell. The sea butterfly cannot survive without its shell.
In 2014, PBS reported on a National Oceanic and Atmospheric Administration study that found that more than 50% of pteropods, including sea butterflies, sampled from between central California and northern Washington had “severely dissolved shells.” If the sea butterfly population declines, then herring populations decline. It’s a short food chain jump from this to negative effects on humpback whales.
Right now, in my Alaska backyard, the whales are doing fine. They are rhythmically breathing. They do not know what awaits these cold waters that must absorb more and more carbon. For decades the oceans have acted as a buffer against global warming, absorbing roughly a quarter of the carbon dioxide that we emit from burning fossil fuels. The ocean also absorbs more than 90% of the excess heat trapped on Earth by carbon dioxide and other greenhouse gases.