Seeing the Oysters for the Reefs

Artificial reef structures at an oyster restoration site at Alabama Port

[Editor's note: The following post is written by Dr. Rob Brumbaugh, Restoration Program Director for The Nature Conservancy’s Global Marine Program.]

If you clear-cut a forest leaving only the stumps behind, would you still call it a forest? Probably not. Everyone knows you need trees to make a forest.

Unfortunately, it seems we don’t have that same perspective when it comes to managing some of our coastal areas, like oyster reefs.

I recently co-authored a study with a number of my Conservancy colleagues and more than a dozen scientists from other research institutions and management agencies around the U.S. We took a close look at where oyster reefs exist today, as well as the actual biomass (the “living weight”) of the oysters on those reefs. We did this at nearly 40 estuaries throughout the United States, and then compared those numbers with records from 110 years ago.

Oysters have always been a valuable resource, and in the late 1800s government surveyors mapped out the acreages and estimated the amounts of oysters available for harvests in bays throughout the U.S. Collectively, their historic and amazingly detailed accounts give us incredible insights about the abundance and condition of oyster reefs in the past. When we compared the reefs described in the past with the reefs we see today, we learned some things that will shape our conservation and restoration work in the future.

First, we learned that the area in coastal bays taken up by wild oyster reefs has declined by 64%. That by itself wasn’t a shock. The head-turner was the realization that the total “living weight” – meaning actual live oysters versus bare or broken shells of formerly vibrant reefs – had dropped by a whopping 88%.

What does that mean?

A reef without a lot of real, live oysters isn’t much of a reef; it’s a remnant of one that will disappear beneath sediment pretty quickly without some kind of restoration. And, just as a field of tree stumps won’t produce oxygen, scrub carbon dioxide from the air or provide a home for songirds, these remnant reefs are probably not providing all the benefits we expect from healthy reefs – like filtering water, removing nutrient pollution, or producing fish.

The good news (yes, there is good news!) is that this reinforces our current push for restoration of coastal habitat, and of oyster reefs in particular. These findings will also provide a powerful baseline – a clear vision of how things were and are now – to help us measure progress. It lays the foundation for establishing meaningful goals: how many fish do we want to produce? How much water should we filter?

Restoration is happening all across the country and in fact, the U.S. is leading the world in turning things around for these habitats. In the last 15 years, The Nature Conservancy and NOAA have teamed up to do more than 130 restoration projects, including scores of oyster reefs. In doing so, we’ve learned a lot about how this benefits local communities and the people who care about clean coastal waters and abundant seafood.

Since a single oyster can filter up to 30 gallons of water every day, clearing and cleaning it for the benefit of other marine life, just imagine what restoring billions might do for your favorite coastal bay.

Is it worth the investment? I think so. But if (like me) you’re a numbers person, stay tuned for my colleague Timm Kroeger’s upcoming blog on the economics of reefs. If you thought tiny slimy bivalves couldn’t pull much weight and earn a wage, you’re in for a treat.

[Image: Artificial reef structures at an oyster restoration site at Alabama Port. Image source: Andrew Kornylak]

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