Wetland Woes

Land reclamation was once considered an effective, if not the only, solution to Hong Kong’s land shortage problems. It is not surprising then, that our neighboring city Shenzhen is following in our footsteps, reclaiming stretches of land around the border to meet with the area’s rapid economic development.

Recently, numerous cracks have appeared in the ground where land has been reclaimed. Ten-centimeter gashes in the earth have been reported in the coastal Baoan District, leaving walkways tilting and many residents in fear of building collapse. This type of shoddy reclamation is just one symptom of the wider ecological damage that is being wreaked on the area. As China’s economy has boomed, Shenzhen’s wetland area, which is ecologically part of our Mai Po Wetland in Yuen Long, has sadly shrunk. Since 1990, 304 hectares of wetland conservation area has been reduced to around 100 hectares in order to pave the way for further development. However, such rampant development may be harming not only Shenzhen’s environment, but Hong Kong’s too. Hong Kong and Shenzhen share a large body of water—what is known here as Deep Bay is called Shenzhen Bay over the border. Reclamation is found all along Shenzhen’s coast, a large part of which is made up of the wetlands.

Mai Po is recognized as an internationally significant wetland, and one of the major stops for up to 100,000 migratory birds flying from Arctic Siberia and Central Asia to warmer climes, such as Australia and New Zealand. Bena Smith, Mai Po Reserve Manager with the WWF, says reclamation on the Shenzhen side of the bay is changing the shape and shrinking the area of both inner and outer Deep Bay. This is affecting the Bay’s natural hydrodynamics. In particular, it is causing a reduction in fresh water circulation. “When less water enters the bay from the mainland side, there is poorer circulation. The water in the bay then becomes less salinic and waterborne pollutants less diluted. These factors cause long-term damage to wildlife in the bay,” he says. “Pollution can affect invertebrates living in the mud in Deep Bay, and can thus influence the birds that feed upon them,” adds Professor David Dugeon, an ecologist from the Department of Biodiversity at the University of Hong Kong. “Pollutants such as pesticides could reduce the abundance of invertebrate food for birds, and this is a big potential problem for migrating birds that rely on Mai Po as a place to feed and store up energy for their next long flight.”

Sediment accumulation is another problem that could gravely affect the wetland area. “Both sides of the border have the potential to affect what flows into the bay,” adds Dugeon. “This is especially applicable to the Shenzhen side as it is responsible for much of the sediment accumulation within Mai Po, which makes the marshland drier and more terrestrial.” The drying-up of a wetland would hugely affect the biodiversity of the habitat, and certainly impact the food sources for migratory birds.

Besides rampant reclamation, there have been other environmental impacts on Shenzhen that could potentially affect Hong Kong’s wetland ecology. The most recent occurred in February last year. A landfill site collapsed and the toxic silt and sewage underneath the surface were flushed into the Buji River, a branch of the Shenzhen River that ultimately leads into Deep Bay. Fortunately, the mainland government put up barriers to stop the pollutants from getting into the main stream, and according to monitoring results from the Environmental Protection Department, the incident did not cause any serious pollution to Deep Bay. But it is a troubling sign of what could happen.

Another mishap occurred in the mid-90s. The Shenzhen government introduced a fast-growing exotic species of mangrove, Sonneratia, to replace the native mangrove that had been lost due to reclamation. This led to a non-natives species invasion that has affected not only Shenzhen but Hong Kong too. The problem is still ongoing.