The world is my oyster, or so a Shakespearean character once said. That old saying, still alive in modern English, makes oysters a metaphor for "something from which a person may extract or derive advantage."
And oh, how true that turns out to be in a literal sense.
Humans have been extracting advantages from the humble oyster for centuries, as writer Rowan Jacobsen's insightful new book, "The Living Shore: Rediscovering a Lost World," points out.
Oysters are vitally important "ecosystem engineers" in several ways. They act as water filters that keep estuaries from becoming algae-choked dead zones, their reefs act as breakwaters that help reduce shoreline erosion, and their shells form the infrastructure for seagrass and many other species to thrive.
Jacobsen puts it this way:
More than 300 species have been counted on oyster reefs. You couldn't design better habitat....Oysters create the condos, streets, schools, restaurants, parks, and even the water treatment plants of thriving undersea communities, and the great conversation of life begins.
And yet humans seem bent on destroying them---about 85 percent of the world's oyster reef populations have vanished since the late 1800s, according to a Nature Conservancy study published last year. After crunching these and other disheartening numbers, the study's authors concluded that "oysters reefs are one of, and likely the most, imperiled marine habitat on earth."
Part of the problem, as you might have deduced, is that oysters are tasty. Darn tasty. Native populations in America's Pacific Northwest have known that for millennia, says Jacobsen, who calls oysters "the ham sandwich of 1000 B.C." (Salmon were a more prized entree, but clams and oysters were plentiful and easy to get.) He points to the evidence of huge mounds of discarded shells---called middens---that date back at least four thousand years. The size of the shells tends to diminish as the height of the pile rises, suggesting that even native populations weren't exactly sustainable eaters.
They still followed the usual trend of eating their way through a shellfish community faster than the community could replenish itself. But for thousands of years, human populations on the coast were small enough to simply move on to the next, unexploited beds, allowing the exhausted beds to recover.
And then came the Gold Rush, and a rush of settlers with mighty appetites, and you can guess what happened next. The native Olympia oyster population in San Francisco Bay was utterly exhausted by 1910, according to Jacobsen.
When he turns to the East Coast, the news gets even worse. In a bleakly terse chapter titled "How to Kill A Bay," he explains how pollution, over-development and over-harvesting combined to destroy both the Chesapeake Bay and its oyster population.
But for all the depressing news, it's actually a gorgeous little book, anchored to the narrative of Jacobsen's journey with a group of marine scientists searching for the remnants of what was once a thriving population of Olympia oysters off the coast of British Columbia. He includes an appendix listing several groups that are working to restore and conserve oyster reefs; a hopeful ending.
As a consumer, this doesn't mean you must avoid oysters---even Jacobsen still eats plenty of them. In fact, farmed oysters (95 percent of what's available these days) are considered a "best choice" on the Monterey Bay Aquarium's sustainable seafood guide. Turns out the farms are good for coastal ecology (unlike many salmon farms). But if you're concerned, you could go the extra mile by buying only from fisheries which have been certified as sustainable.