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Can Oysters Save Our Seas?

Oysters are one of the few crops that are hard to overfarm—and they come with a bevy of ecological benefits.

Oysters get inspected in Maryland.
Edwin Remsberg
Oysters get inspected in Maryland.

You know who had a weirdly great 2020? “Oysters,” Rachel Dean told me. Oysters grew fatter and faster than expected last year, and diners frequently weren’t around to eat them.

Rachel and her husband, Simon, are harvesters (known as “watermen”) in the Chesapeake Bay. “We’ve had a great wild fishery this year, it’s been really robust; it was last year, as well,” she said. “We can’t sell everything we’re catching all the time.”

It can be hard to tell, from one year to the next, how the bay’s oysters are doing. In 2004, they appeared in crisis, with only 26,000 bushels harvested. But then, through a combination of restoration, sustainable practices, and aquaculture, the numbers began to climb back up, reaching 900,000 bushels in 2015. Harvesters like the Deans are able to make a full or partial living from the water once more, much to the delight of oyster lovers.

It’s also good news for the environment and the communities around the Chesapeake. Oysters provide crucial environmental benefits in a changing climate, even when they are farmed. And unlike other crops, it would be difficult to overfarm them.

Accounts from the seventeenth century describe the Chesapeake Bay as clear, clean, and overflowing with marine life. Fish darted through the seagrass, and crabs scuttled over oyster reefs, some of which towered so high, they broke through the water at low tide. Even in the late 1800s, at the height of the oyster trade, there were billions of oysters in the bay. Watermen harvested about 20 million bushels of oysters a year, compared to a few hundred thousand now.

Until the turn of the twentieth century, oysters could filter the entire bay in a day or so; now, it takes about a year. Overharvesting in the late 1800s and early 1900s led to sharp drops in oyster populations, to the detriment of everything they supported—the reefs serving as habitat for fish and crabs, the water that was filtered regularly, the people who ate them. Disease and pollution slowed oysters’ recovery. But at long last, they seem to be stabilizing—and understanding the lessons learned in the bay could help other watersheds protect and restore shellfish sustainably.

“They filter the water at fairly incredible capacities,” Dr. Brandon Puckett, research coordinator at the North Carolina Coastal Reserve and National Estuarine Research Reserve, told me. Oysters pull sediment from the water, making it less murky; they process nutrients like nitrogen and phosphate, which runs into the water after nearby farms are fertilized; and they reduce the growth of algae and plankton, keeping the water clear and healthier for other marine life.

Oysters also provide some protection from the disruptions of climate change. While more frequent and powerful storms and rising sea levels can erode coastlines and damage communities, oyster reefs halt or slow those waves and reinforce the strength of shorelines. “Living shorelines provide not only ecosystem services benefits for things like fish and crabs, but also provide flood retention and opportunities to reduce wave energy before it affects land,” Chris Moore, senior regional ecologist at the Chesapeake Bay Foundation, told me.

Oyster restoration for ecological purposes is still a pretty new and evolving science, Moore said, dating back only “20 to 25” years. The Chesapeake Bay Foundation has a program now to restore oyster populations in 10 tributaries by 2025, and the Commonwealth of Virginia recently promised $10 million in funding for restoration projects like these. Restored oysters are usually placed in sanctuaries, so they won’t end up on our plates. But the oysters in protected areas release larvae that float through the water and can settle elsewhere, boosting wild populations.

The foundation also has the separate but related goal of adding 10 billion new oysters in the bay by 2025, through not just restoration but also aquaculture. Aquaculture, or seafood farming, means that more oysters go into the water each year, taking some of the pressure off wild oysters and generating jobs and income. Farmed oysters usually don’t reproduce, so they don’t add to future populations, but they still filter the water and provide important habitat for other species as well. “The number of species that inhabit oyster reefs and benefit from them is really impressive,” Puckett said. (In places where oysters don’t thrive, especially in fresh water, some organizations are beginning to restore mussels, which offer many of these same benefits.)

Given oysters’ ecological value, eating them might seem counterproductive. “We like to harvest oysters, and I consume them myself—love them,” Puckett said. “But it’s a bit of a double-edged sword. You’re removing the individual oyster from the water but also the habitat for subsequent generations of oysters.” However, he said, watermen and officials have been figuring out over the past few decades what level of harvest is sustainable to keep diners happy and harvesters employed. And as populations rebound, so far the formula seems to be working. Perhaps paradoxically, the more we consume oysters, the more motivated we may be to conserve them, Puckett said. “As a society, we tend to protect what we treasure.”

There are limits on how much oysters can reverse the damage we’re wreaking on the planet. Protection and restoration can help, Puckett said, but “you’re not going to oyster your way out of bad water quality. You can’t just do nothing upstream and dump it all in, and hope the oysters take care of it all.”

“They can’t save the bay,” Dean said. “But I do think they certainly help.” She sees oyster populations as an indicator of the bay’s health—“the canary in the coal mine when it comes to water quality.” Looking at how well oysters are doing can help officials gauge what land use policies are working or need to be strengthened. The bay is only as healthy as the land around it: Fertilizer from farms, pollution and rainwater from roads and housing developments, and wastewater management are all factors feeding into watershed health, experts told me.

Much of this happens at the policy level, but individuals can help, too—for instance, by fertilizing our lawns less. Individuals can also return opened oyster shells to watermen and conservation organizations. Oysters prefer to attach to a certain kind of surface, so watermen and conservationists reuse the shells to rebuild reefs. Usually, restaurants return shells, but if you buy a bushel of oysters to eat at home right now, you can also help by giving the shells back. “Don’t simply throw that oyster shell away. Take time to recycle it. It’s extremely important, in terms of helping the oyster population recover,” Moore said.

Although oysters have been plentiful this year, business has not: It’s been difficult for harvesters to change course from serving restaurants to delivering at home. For at-home diners who still have disposable income, eating oysters can be a way to support local businesses with environmental advantages. For many people, though, such possibilities feel increasingly out of reach. The week before Christmas, Dean loaded three bushels of oysters in the back of her white pickup truck and headed to her local food pantry, handing out bags of two dozen oysters to anyone interested. “If any year was a good year to give,” she said, “this was it.”