Kate Wing's Blog
Fewer eggs, fewer baskets
March 24, 2008
Posted by Kate Wing in Reviving the World's Oceans
The idea of a diverse portfolio is a common theme in financial discussions. If you happen to have any money these days, the experts would tell you to spread it around to maximize your returns and reduce your risk. Putting all your money in a savings account is safe, but earns you less interest than putting some of that money in savings and the rest in the stock market. Sinking all your cash into a house in California may have seemed like a wise investment, but now, perhaps not so much. Let’s hope there are some Canadian loonies hiding under the couch cushions.
Animals have evolved similar strategies to cope with the changing environment that affects their most valuable asset – their offspring. Older female Pacific rockfish give their tiny planktonic young more food in the form of a large oil globule, letting the larvae survive longer until they find a suitable rock to call home. Since rockfish are also known to be cannibals, the juveniles don’t always live near the adults. These diversifications have helped many species survive the many milder fluctuations on ocean temperature and productivity. With global warming pushing sea surface temperatures beyond the range marine wildlife has grown accustomed to, animals are reaching their limits. Including the king penguins.
This piece by Le Bohec et al in the Proceeding of the National Academy of Sciences gave me a grave sense of unease. 2/3 of the world’s king penguins live on the Crozet Archipelago where they breed year-round. Penguins need high calorie prey available year-round, preferably close to their rookery. Warmer water temperatures may reduce the extent of the ice shelf, but they also negatively effect the penguin’s prey, making them less numerous and pushing them further offshore. Warmer ocean temperatures are hitting penguins in both the winter and the summer, making it harder to feed their young and harder just to make it through the winter. Previous El Nino events caused lower recruitment and lower adult survival, but as those events were relatively short, colonies could recover.
Here’s a quote from the discussion:
“..according to life history theory in long-lived species, king penguin populations would not be sustained with a 9% drop in their adult survival such as that we show for an increase of only 0.26C in SST.”
They then cite an IPCC that global surface temperature is predicted to increase by 0.2 per decade for the next two decades. There’s not a one to one ratio between surface temperature and SST, but this is not good news for the penguins. They’ve already tried spreading their foraging out over time and space, but those distances are getting longer and the seasons are less productive. There’s only so diverse your survival portfolio can be at the bottom of the world.
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