China's new Great Wall is not for the birds
More than half of China's tidal flats around the Yellow Sea have been smothered by development over the past 50 years, driving migratory shore-birds out of vital resting and foraging grounds. And with construction of the new “Great Wall of China” expected to continue apace, scientists say the tidal flats now qualify as an endangered ecosystem under new IUCN criteria.
The Yellow Sea's primary coastal habitat – tidal flats – extend across northeastern China and along the Korean Peninsula. The flats are home to numerous invertebrates and vertebrates (including fish and avifauna), forming complex communities that depend on regular tidal inundation. More than three million shorebirds migrating between the Arctic and sites in Asia and Oceania stop over on the flats each year. However, the low cost of developing coastal lands and the scarcity of land elsewhere also make the tidal flats attractive to developers. “The flats in some areas are up to 20 km wide; they're reclaimed for alternative land uses across the entire Yellow Sea coastline”, explains conservation biologist Nick Murray (University of New South Wales, Sydney, Australia). “Unconstrained development is resulting in a hard wall of reclaimed land along the Chinese coastline that is expected to be part of an 1800-km-long urban corridor by 2030.”
In a study published this year (Austral Ecol 2015; doi:10.1111/aec.12211), Murray and fellow researchers Richard Fuller (University of Queens-land, Brisbane) and Ma Zhijun (Fudan University, Shanghai) concluded that the Yellow Sea tidal flats are at a turning point. As well as the loss of area, evidence of an ecosystem under pressure includes declining commercial fisheries stocks, increased prevalence of hypoxic zones, more jellyfish and harmful algal blooms, and dwindling numbers of migratory birds in Australia and Japan. While the problem is increasingly recognized by governments, a comprehensive development plan incorporating ecosystem conservation remains elusive. Tidal flats are frequently reclaimed for aquaculture development, which is often just the first step to permanent loss. “Agriculture often follows, with harder structures like urban development and ports a frequent next step”, warns Murray.
Satellite imagery indicates that while tidal flats have disappeared rapidly in China and South Korea, they have held their own and even increased in North Korea (Front Ecol Environ 2014; doi:10.1890/130260). “It may provide somewhere for migratory birds to continue their migration”, says Murray, “but it's still concerning because it seems to be due to increased sediment in rivers from North Korea clearing its forests.”