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      Oysters transform coastal seas

      Writer: Matteo Convertino  |  Editor: Zhang Chanwen  |  From: Shenzhen Daily  |  Updated: 2023-11-02

      Bio terraformation is the process of preparing extraterrestrial planets for life by creating habitats and a suitable atmosphere. Similar efforts can be carried out on Earth to restore lost habitats or enhance existing ones.


      Pak Nai natural oyster reefs. Courtesy of The Nature Conservancy in Hong Kong


      Oysters are particularly useful in this regard due to their collective behavior, which stabilizes sediments, filters water, and increases biodiversity in coastal marine ecosystems. A single oyster can filter 7 liters of water per hour, and the carbon sequestered in the shells of oysters harvested annually is roughly 10% of the total blue carbon stored in coastal wetlands per year. Restoring oyster reefs is crucial for reversing global ecosystem declines and preserving marine ecosystem functions, not to mention the economic benefits. However, uncertainties in the dollar value of oyster reefs and certain conditions required of restoration sites hinder the potential for global-scale restoration.


      Over the past 50 years, there has been a shift from natural reefs to rapid and massive aquaculture farming of oysters. As a result, many oyster reefs in areas such as Shenzhen and other parts of the Greater Bay Area have disappeared, leading to the loss of ecological value and the local supply chain, as well as the disruption of coastal diversity corridors. It is imperative to predict the potential distribution of oyster reefs, quantify their ecosystem benefits and economic value, and consider local hydro-climatic risks that oysters can mitigate.  


      A man prepares oyster in Shekou , Shenzhen. Most of the oysters come from elsewhere other than Shenzhen (typically from Hong Kong). Matteo Convertino


      Light at the sea bottom and primary productivity are the dominant environmental variables governing the global distribution of oyster reefs. Only about 13.8% of high-suitability areas in eight hotspot countries are incorporated into marine protected areas, highlighting the need for protection. China is the 7th oyster restoration hotspot in the world in terms of total benefits, despite being the largest producer and consumer of globally farmed oysters.


      Several hotspots in the Guangdong-Hong Kong-Macao Greater Bay Area, including Shenzhen Bay, Yantian port, Nan'ao, old Dapeng Town, and Hong Kong are deemed oyster habitats due to the presence of tidal flats, mangroves, and seagrass that facilitate oyster aggregation. However, questions remain about water quality, restoration of hydrological corridors, climate stress, and stakeholder desirability for restoring oyster reefs in these areas.


      Restoring oyster reefs through habitat rewiring or rewilding is crucial for climate engineering and habitat improvement. Oysters can play a role in rewiring coastal ecological corridors, which has global and local positive effects on carbon sequestration in addition to other benefits. Oyster shells can be used for concrete by developers.


      Many estuarine areas in the Greater Bay Area have the potential as oyster reef restoration sites, and effort is worthwhile for governments to consider this nature-based solution to improve the marine ecology.


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