Oyster Beds
THE OYSTER BED: AN ICONIC COASTAL HABITAT TYPE THAT HAS NEARLY VANISHED
In temperate estuaries around the world, there are three vital habitat types created by living organisms – oyster beds, seagrass beds and salt marshes. Oyster beds, created by generations of oysters growing on each other, are analogous to coral reefs in tropical waters. But while coral reefs still exist today, very few extensive, intact oyster beds remain on the Pacific coast of North America. California in particular has lost virtually all representation of this distinctive, vital habitat type which not only supported dense oyster populations but also generated a myriad of other functions, such as providing refuge for small animals and improving water clarity.
Today, many conservation groups are trying to bring back this lost habitat type. Tribes and First Nations are sometimes also involved, because harvest from dense, sustainable oyster beds is culturally important and part of a return to food sovereignty.
But particularly in estuaries where conditions have become muddier due to human land uses, bringing back oyster beds poses a challenge. To thrive and persist, new oysters would need to settle on existing beds, consisting of living oysters cementing to the legacy shells of dead oysters, in such high numbers that the upward growth of the bed outstrips the rate of sedimentation and legacy shell degradation. So bringing back oyster beds involves both providing them initial hard substrates to become established and ensuring oyster numbers in the estuary are high enough to provide lots of new juvenile settlement in the future.
Most people in California have never seen a live Olympia oyster. If they’ve seen one, it has probably been on an artificial structure put out in the estuary by humans, such as rip rap and pilings. But if we had a time machine, what would we have seen? The most intact oyster beds around today exist in Washington and British Columbia, and hold clues. There is not one single look to an Olympia oyster bed. Sometimes oyster beds are very dense, with oysters the dominant species, growing on each other and bits of shell. Sometimes they form more sparse and ephemeral clusters, mixed in with mussels or gravel or seagrass, but are still prominent components of the mudflat community. Because oyster beds have almost entirely vanished from many estuaries, particularly in California, people don’t even know what has been lost, and aren’t motivated to support bringing them back.
This is what is called a shifting baselines problem – without a vision of the glory of functioning, healthy beds, no one will advocate for them. Ironically, a kid in California is more likely to care about saving coral reefs than the reefs in their own backyard, Olympia oyster beds. But the more people learn about the value of oyster beds, eelgrass beds and salt marshes, the more energy and support there will be for bringing back these natural habitat types to our coast.
