With 90 percent of the new seawall already built, ornithologists say many endangered waders face eviction. These include the spoon-billed sandpiper which breeds in northeast Russia. Famous for its bizarrely shaped bill, the species is down to less than 500 breeding pairs.
"The tidal mudflats in Korea, particularly Saemangeum, are vital for the survival not only of migratory birds in eastern Asia, but also for the marine ecosystem of the Yellow Sea," said Simba Chan, a Korean bird expert from the Wild Bird Society of Japan.
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The WSG argues that waders are sensitive indicators of environmental change and that closer monitoring of these birds would help detect problems in the wider environment.
For instance, Clark says odd behavior by oystercatchers in Britain in the late 1990s indicated the collapse of shellfish beds in the Wash, off England's east coast. An important fishery for cockles and mussels, large numbers of oystercatchers feed in the Wash, where they winkle out the shellfish with their orange bills at low tide.
Clark said: "People were reporting oystercatchers hunting for earthworms in the middle of busy roundabouts. They were also seen in suburban back gardens. We discovered this was because there was no food left for them along the shore."
A similar problem has been identified in Holland's Wadden Sea, a staging site for many long-distance migratory waders. The WSG says scientific evidence suggests unsustainably high levels of shellfish harvesting have caused serious declines in several species.
Clark added: "Instead of taking shellfish in traditional ways, fishermen are using large boats which scoop everything off the bottom. Birds are being forced to move elsewhere to look for food."
The WSG conference also highlighted concerns that many waders, including the globally threatened slender-billed curlew and sociable lapwing, are highly susceptible to population crashes because breeding success is dependent on the birds gathering in large flocks.
The Royal Society for the Protection of Birds, Europe's largest conservation charity, says the sudden collapse in slender-billed curlew numbers in the 1960s has left the bird on the brink of extinction.
"This species is in very serious trouble, with no more than a few hundred left," said John O'Sullivan, from the RSPB's Global Programmes Department. "We don't know where they breed and the only evidence they still exist comes from rare sightings of migrating birds in southeastern Europemaybe one or two a year."
The birds, which once wintered in huge flocks around the Mediterranean, have probably fallen victim to agricultural disturbance at former breeding sites somewhere in the Russian or central Asian steppes, said O'Sullivan.
He added: "This species is believed to be numbers-dependent, having adapted to breed in colonies. The downside is they don't feel comfortable breeding alone, or in small numbers. So when they should be nesting they are wandering about looking for each other."
Dwindling populations have also left many waders vulnerable to the accumulated effects of harmful genetic mutations, so accelerating the plunge towards extinction.
The WSG says 140 wader populations have now fallen below 15,000 individuals, 28 percent of the global total.
The Cadiz conference noted that in 2002 the World Summit on Sustainable Development called for "a significant reduction in the current rate of loss of biological diversity" by 2010.
But the Wader Study Group now concludes: "The declines reported from all over the world suggest that, for waders at least, it will be extremely challenging to achieve these targets."
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