The Deep Bay, at the border between Shenzhen and Hong Kong, was originally the site of prime aquaculture in both cities. At the mouth of the Shenzhen River lies Mai Po, an ecologically sensitive wetland that is protected under the Ramsar Convention and managed by the World Wildlife Fund. The Mai Po “Marshes” are not only valued for their natural ecological conditions, but an artificial ecologic phenomenon that began in the 1950s when the influx of immigrants constructed “gei-wai’s” (tidal shrimp ponds) that replaced the original mud flats. Currently, the 230 hectares of gei-wai’s are no longer economically productive, but during the winter months, Mai Po attracts over 55,000 migrant birds to feast on the rich supply of invertebrates exposed by the annual drainage of the shrimp ponds.
The shoreline of the Deep Bay is an apt example of differentiated urban development in Hong Kong and Shenzhen. On one side, Shenzhen has reclaimed land and built up the city right to the water’s edge; on the other, Hong Kong has retreated from this edge and populated the shore with landfills, power stations, or other infrastructure. The 5.5km 2007 Hong Kong Shenzhen-Western Corridor connects the two cities over the Deep Bay and is one of the six border crossings that facilitate interaction between the two cities. The bridge corridor is a joint venture between Shenzhen and Hong Kong and its architectural expression symbolizes a collaborative spirit between the two regions. It also signals the beginning of a new understanding of the Deep Bay as continual territory instead of a site of oppositions, suggesting a collaborative urban future that is rooted in ecology, economy, and exchange.
Climate Change or Natural Sedimentation?
The Deep Bay is a shallow sediment shelf with an average water depth of 3 meters. Mai Po Ramsar Site and Futian Nature Reserve are both important habitat areas with valuable mudflats, mangroves, and aquaculture ponds, all sensitive to potential sea level rise. These habitat types rely on gradual and shallow slopes within intertidal zones and can only survive within certain water depths. Sea level rise would reduce the amount of space available for a large number of species because current urban development restricts their upland migration. However, recent observations show that the natural sedimentation rate in the Deep Bay exceeds the potential rise in sea levels and encourages the expansion of mangrove forest sea-ward.