Oysters are more than a tasty appetizer. The mollusks are key players in healthy marine environments. The filter-feeders improve water quality, and their beds provide habitat for fish and other underwater critters. Oyster beds also improve life out of the water, preventing coastal erosion and creating a buffer against large waves.

As oysters’ role in maintaining a vibrant coastal ecosystem becomes more clear, environmental groups are trying to bring back devastated oyster populations. In some places, this means getting restaurants to recycle their leftover oyster shells to put back into the ocean instead of sending them to a landfill, according to Fast Company.

This is particularly important along the Gulf Coast, where the Alabama Coastal Foundation (ACF) set up a recycling program in 2016 to collect used oyster shells from local eateries. According to The Nature Conservancy, 67 percent of the U.S. oyster harvest comes from the Gulf of Mexico [PDF]. The Nature Conservancy has been working throughout the Gulf of Mexico to restore oyster populations.

So far, the effort in Alabama, a partnership between the waste collection company Republic Services and the ACF, has collected enough oyster shells to cover 7.2 acres of sea floor. The program is currently funded by a grant from the National Fish and Wildlife Foundation and is free to restaurants, though that may change in the future.

Alabama isn’t the only place oyster shells are becoming a hot commodity. In New York City, the Billion Oyster Project is working to restore oyster populations and reefs in New York Harbor, in part to make Staten Island more resilient to superstorms and flooding. (Hurricane Sandy ravaged the island's east and south shores in 2012.) In New Jersey, the American Littoral Society is seeding local waterways with new oysters in Barnegat Bay in hopes of both restoring the once-vibrant oyster harvesting industry there and cleaning the waterways. Other oyster repopulation projects are ongoing in the Chesapeake Bay and along the Gulf Coast from Florida to Texas. On the West Coast, the Puget Sound Restoration Fund plans to restore 100 acres of native oyster habitats by 2020.

However, oyster habitat restoration isn’t as easy as it sounds. In a 15-year study of Rhode Island’s oyster restoration programs, the oysters had such a high mortality rate that populations began declining immediately when the programs stopped actively re-seeding the beds with new oysters. Another worldwide study found that the median survival rate for oyster bed restoration projects was only 56 percent.

As many current oyster restoration projects are just gaining steam, it may be years before we find out if they can be as effective as natural oyster beds.

[h/t Fast Company]