Fisherman's Wharf might be the last place you would look for a problem that could threaten human existence -- all the seafood for sale, any day.
"I feel like I am walking through a museum," said Sven Huseby.
One filled a hard-shelled ecosystem we take for granted, but not Sven Huseby and his wife Barbara Ettinger.
"Already, fisheries are in decline," said Huseby
"It's important to our very survival," said Ettinger.
It is an issue most of us never heard of -- ocean acidification, and it is the subject of a film they have just released called 'A Sea Change.'
"We want ocean acidification to become a household word," said Ettinger.
Ocean acidification is like the evil twin of climate change. Not only is our air getting warmer, but our oceans are becoming more acidic. The culprit in both cases is carbon dioxide from fossil fuels.
"Thirty percent of human protein comes from the ocean," said Huseby.
When carbon lands in oceans, it interacts with water forming an acid. Now, scientific research shows that after 250 years of absorption, the ocean's chemical balance has changed to a point where that acid has begun dissolving the shells of some organisms.
Among them is the pteropod, a fundamental staple at the bottom of the food web. If this species goes extinct, others could tumble like dominoes.
"As a result they get thinner shells. They get picked off by other creatures. They have decreased fertility, and we see numbers decrease," said Huseby.
And so Sven's and Barbara's odyssey, as documented by the film, went pretty much to the ends of the earth in 18 months.
They went as far north as the Arctic Circle, where they watched ancient glaciers falling into the sea at an alarming rate.
"I probably have not seen anything more numbing or awe inspiring," said Ettinger.
We should note that that Sven Huseby did not begin life as a professional film maker. He spent 30 years teaching.
With this movie, it appears that his classroom just got bigger.
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