Wild Oysters Deemed 'Functionally Extinct'

by Katie Horner | February 10, 2011

A recent Valentine’s Day-inspired article in the Grist pointed out that oysters are the only delicacy that enhances The Mood and water quality. Don’t get too excited, though: a new study published this week in BioScience revealed that oysters are “functionally extinct” in many parts of the world where they were once abundant, and nothing kills The Mood (or mollusks) like functional extinction.

Today about 95% of all oysters served in restaurants and sold in markets are farmed, a result of the fact that overfishing has destroyed more than 85% of global oyster reefs. In places that were once famed oyster harvesting spots, only 1% of reefs remain; in fact, five locations in North America contain 75% of remaining global oyster reefs.

Estimates indicate that at the current rate of decline, wild oysters could disappear within decades if nothing is done to remedy the situation. This possibility is so alarming because oysters play a crucial role in the coastal ecosystems they inhabit. Not only do the mollusks filter impurities from the water and support fish populations, but they also prevent coastal erosion: over time, shells of deceased oysters form reefs, which mitigate the erosion of shorelines.

The importance of oysters for coastal waters and aquatic communities led Dr. Michael Beck (University of California, Santa Cruz) to conduct a study examining the decline of oyster populations worldwide. Dr. Beck and his team of marine biologists studied 144 former oyster beds in 40 regions around the world, making theirs the largest study to date of wild oysters.

Dr. Beck and his team found that oyster reefs are at less than 10% of their prior abundance in 70% of bays and 63% of eco-regions studied and less than 1% of prior abundance in 37% of bays and 28 % of eco-regions. These numbers led Beck to conclude that oysters have become “functionally extinct,” meaning “they lack any significant ecosystem role”.

This is a shocking finding considering the historic dominance of oysters in temperate coastal waters. Like lobsters, oysters were once so abundant they were considered peasant food. In recent decades, however, their status as a culinary delicacy has led to intensive harvesting and many populations have been destroyed by modern fishing methods, especially dredging and trawling, which disturb the ocean floor.

In an ironic twist, the only native oyster populations in the world that had remained at historic abundance levels were devastated last spring. Yes, the healthiest oyster beds in the world (in fact, the only oyster beds in the world deemed healthy by Dr. Beck and his team) were in the Gulf of Mexico, site of the BP Deepwater Horizon oil spill. While in the early stages of the spill it was determined that the oil had not significantly harmed Gulf oyster reefs, subsequent decisions by politicians only made the environmental disaster worse for the oysters.

Only days after the explosion that sent a steady torrent of oil into the Gulf, Louisiana officials and Governor Bobby Jindal decided to open giant valves on the Mississippi River in an attempt to push incoming oil out of the state’s coastal marshes and back out to sea. Although the intentions behind the decision weren’t bad, the deliberation (and consequently the outcome) was poor: state bureaucrats didn’t consider the delicacy of coastal ecosystems or the specific conditions marine organisms need to survive.

The impact of the freshwater diversions from the Mississippi was far more severe than the damage done by the oil. Following his study, Dr. Beck estimates that half of the Gulf’s most productive oyster reefs were destroyed by the decrease in salinity; immediately following the river releases, oyster fishermen along the Louisiana coast reported mortality rates of 80% for thousands of acres of oyster beds. While oyster harvesters are being compensated for their losses through the $20billion BP compensation fund, the oysters themselves aren’t so lucky.

At the end of the grim report, Dr. Beck offered hopeful suggestions, recommending that all areas where less than 10% of former oyster reefs remain be closed to harvesting, dredging and any activity that could harm remaining oyster stocks. Dr. Beck was quoted in a NY times article as saying that although oysters “are already functionally extinct [in many places]… if we act now with reasonable measures, we can get them back”.

So what measures should be taken? One possibility is re-introducing oysters into waters that they once inhabited, as suggested by one New York artist. Last year, Kate Orff presented her idea to reintroduce oysters into the waters around New York City as part of the MoMA’s “Rising Currents” exhibit. Orff proposed creating oyster farms in New York harbor and the Gowanus Canal; the oysters would filter (and thus improve) polluted waters and the rope structures that would comprise their beds would mitigate storm surge.

While initially presented as part of an art exhibit, Orff’s design has real potential. Students at the New York Harbor School have already begun experimenting with oyster farms in city waters. More important than the physical outcome of Orff’s idea, however, is the way in which it demonstrates and promotes innovative thinking. Orff’s New York oyster beds may not be the type of measure Dr. Beck had in mind for revitalizing oyster stocks but, the idea of finding a single solution for multiple problems may be the type of approach necessary for revitalizing the global environment.

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