Scientists have identified vast stretches of coastline where oyster reefs could thrive but are currently largely absent. An estimated 85% of the world's oyster reefs have disappeared over the past century, taking with them ecosystems that protect shorelines, support marine life and help clean coastal waters. A new study argues that restoring them could unlock ecological benefits worth trillions of dollars.
The research, published in the journal Frontiers in Marine Science, uses the concept of gross ecosystem product (GEP). Unlike conventional economic measures, GEP puts a value on services such as water purification, carbon storage and coastal protection. As Dr. Matteo Convertino, an associate professor at Tsinghua University and the study's lead author, explains, fully restoring reefs in the ten countries with the greatest potential would generate a GEP of $12 trillion.
Oyster reefs do much more than provide seafood. As oysters filter water, they remove suspended particles, while the surrounding ecosystem helps regulate nutrients. These underwater structures also reduce wave energy along coastlines and provide feeding grounds, shelter and breeding grounds for fish and invertebrates.
The researchers calculated that if reefs covered all the suitable areas identified by their analysis, they could filter enormous amounts of water. In the United States alone, the estimated potential reached 77.58 quadrillion liters. Across all the regions in the model, restored reefs could also sequester up to 12.3 million metric tons of carbon annually. For the US, the combined potential annual value of water purification, nitrogen removal and carbon sequestration was estimated at $25.1 billion.
To identify where reefs could thrive, the researchers analyzed thousands of reef records with geographic coordinates from two public databases. Using machine learning, they predicted which habitats are suitable based on conditions such as water temperature, salinity, light availability, nutrient concentrations and dissolved oxygen.
The analysis identified ten countries with particularly high potential: the United States, Australia, Chile, China, Japan, South Korea, Argentina, France, Germany and Italy. Together, they have around 295,000 square kilometers of suitable habitat, or about 6% of their coastal zones. However, known oyster reefs currently occupy only 10% of this area, mainly in bays, lagoons, estuaries and river deltas.
Restoration on this scale would require significant conservation efforts. Only 23% of suitable habitat currently lies within marine protected areas, leaving much of it without formal protection. “We estimated that 90% of suitable areas need restoration, while 80% need protection through conservation action. In other words, the current state of oysters is far from ideal, but there is a huge opportunity given the benefits,” Convertino said.
The $12 trillion estimate nevertheless comes with significant uncertainty. The calculations are based on global averages for ecosystem services rather than direct measurements at each location. Changes in oyster populations, local environmental conditions and the success of restoration efforts could affect the eventual benefits.
Rising temperatures and other climatic changes threaten the long-term survival of reefs in many coastal environments. However, the effects are not expected to be uniform, and some areas could become more suitable for oyster growth. “Because global warming generally reduces the quality of oyster reef habitat, we expect their global GEP to fall from the current potential value of $12 trillion. But some countries may see reefs expand because of more favorable conditions: particularly Australia, Indonesia, South Korea, Japan and France,” he added.
The study is a reminder that nature provides services rarely recorded in national accounts. Even if the figures remain theoretical, they show the scale of what was lost with the disappearance of the reefs and the scope to recover some of it through targeted protection and restoration of coastal ecosystems.
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