Why do Oysters Matter?
Often overlooked, the humble oyster is the unsung hero of our seas.
Starting life as microscopic free-floating larvae, young oysters will settle on hard surfaces – preferably the shells of adult oysters – to complete their development. Over time, as more larvae settle and grow, the oysters build large, dense colonies on top of each other known as oyster reefs.
Oyster reefs provide a multitude of benefits to nature and people. Just one oyster can filter 200 litres of water a day, helping improve water quality in our oceans. Fish, crabs and other marine species find food, shelter and breeding grounds among the shells, with one study in Hong Kong finding six times more biodiversity on oyster reefs than on mudflats.
Cultural Heritage of Oyster Reefs in Hong Kong and the Pearl River Estuary
Oyster reefs were once abundant across the Pearl River Delta, but significant changes began during the Tang Dynasty (618-907). The region saw rapid population growth, leading to extensive land reclamation for farming and increased sedimentation from deforestation. These activities disrupted oyster habitats, as dykes built for water control and farming altered the natural shores and increased mud in rivers, making it difficult for oyster populations to adapt.
Beyond savoring oysters, the harvesting of oysters for lime production, a practice that started over 1000 years ago. Lime, obtained by burning calcium carbonate materials like shellfish shells, was crucial for various industries, including construction and agriculture. The industrial-scale extraction of shells led to the widespread loss of oyster habitats. Archaeological evidence from Hong Kong indicates that coastal oysters were heavily exploited for lime production as early as the Tang Dynasty.
By the early 1900s, the Pearl River Delta was producing thousands of tons of lime annually, with significant contributions from Macau to Jiangmen. In Hong Kong, records show a substantial workforce and fleet dedicated to shell extraction, supporting regional economies such as salt production and construction.
Image © Kyle Obermann
Oysters are an important source of food and income for people, particularly in Hong Kong, where a 700-year-old oyster aquaculture industry forms an essential part of its cultural heritage. In the future, oyster reefs could also shield the city from increasingly severe storm surges caused by climate change.
85% of Oyster Reefs are Lost Globally
Unfortunately, oyster reefs are the most endangered marine habitat on the planet, having declined by 85% globally due to human activities. Hong Kong is no exception to this, with overharvesting, pollution, coastal development and mismanagement having destroyed most of its oyster reefs, leaving the species and oyster farmers who depend on them struggling to survive. Furthermore, with no shell recycling program in the city, oyster shells from aquaculture and restaurants are often discarded in landfills.
Image © Kyle Obermann