I spent most of today walking down a beach and then walking back. Why? Because I wanted to go see a dead whale who had washed up there. Reportedly, her name was Pivot (many humpback whales have been named by researchers. They are are individually recognizable), and she has been known individually to humans for 13 years. That means that however old she was, she was an adult, sexually mature and full-size, despite looking quite small for her kind (at least to me). Her cause of death is not yet known.
Because I was thus occupied, I don’t have time to write a detailed piece. Instead, I did an internet search on “humpback whale climate change.” Here is what I found.
The humpback population of the western Atlantic (to which Pivot belonged) is one of the best-studied whale populations in the world–and it’s not doing well. Over the past fifteen years that their reproduction has been being closely studied, annual breeding success for females has dropped from around 40% to only 20%. That doesn’t mean an 80% failure rate–humpback pregnancy lasts almost a year, so females rarely if ever calve annually even if everything goes perfectly. But the period between successful pregnancies is increasing significantly. That’s enough to slow population growth of this still-endangered species. At least part of the reason is a reduction in the population of the whales’ favored prey species in the northwest Atlantic–humpbacks migrate south to breed in the Caribbean, but they don’t eat on their breeding grounds or on migration. The northwest Atlantic is IT for food. And that food is being threatened by climate change.
Puffins are having a curiously similar problem.
Humpback whales are not only victims of climate change, they are also potential agents of climate change mitigation.
There are several ways humpbacks (and other whale species) contribute to the sequestration of carbon. One is that they move nutrients by eating in one place and peeing and pooing elsewhere–for example, while they don’t eat on their breeding ground, they do still have to pee regularly while there. Since phytoplankton growth is limited by nutrient availability, fertilizer in the form of whale feces and urine will mean more phytoplankton–just a 1% increase in phytoplankton will mean an increase to carbon sequestration equivalent to that of two billion mature trees.
The other way whales help is that when they die, they often sink to the bottom of the ocean (Pivot was an exception here), and much of the carbon in their bodies simply stays down there, eaten by animals who never come up.
There aren’t a lot of whales these days–counting all species together, there are currently about a quarter of the number who lived prior to the age of intensive whaling. If their populations recover fully, that will mean two or three million more whales, each of them fertilizing phytoplankton for decades and then carrying more carbon down to the bottom of the sea, to be replaced by more young whales ready to start fertilizing phytoplankton in turn.
I really hope Pivot’s kids are OK.