A comprehensive new survey that compared the past and present condition of oyster reefs around the globe has found that more than 90 percent of former reefs have been lost in most of the regions where the molluscs were formerly abundant.
Writing in BioScience, the researchers note that in many places, such as the Wadden Sea in Europe and Narragansett Bay, oysters are rated “functionally extinct,” with fewer than 1 percent of former reefs persisting. The declines, they add, are in most cases the result of over-harvesting of wild populations and disease, often exacerbated by the introduction of non-native species.
Most reefs around the globe were rated poor or worse, with the exception of those in the Gulf of Mexico. Beck says that the oyster fisheries there are “probably the last opportunity to achieve large-scale oyster reef conservation and sustainable fisheries.”
As well as a being a foodstuff, oysters provide important ecosystem services, such as water filtration. Beck recommends that harvesting and further reef destruction should not be allowed wherever oysters are at less than 10 percent of their former abundance, unless it can be shown that these activities do not substantially affect reef recovery.