SEOUL (Reuters) - A huge South Korean land reclamation project has destroyed wetlands, killed migratory birds and pushed endangered species toward extinction, a report obtained at the weekend said.

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The Saemangeum land reclamation, completed in 2006 on the west coast and covering about 400 square kms (155 sq miles) -- about seven times larger than Manhattan -- has removed one of the largest feeding grounds on the Yellow Sea for hundreds of thousands of migratory birds who pass by each year, it said.

“Within Saemangeum, (we) recorded a decline of 137,000 shorebirds, and declines in 19 of the most numerous species, from 2006 to 2008,” according to the study by conservation groups Birds Korea and Australasian Wader Studies Group that will be released at an international Ramsar convention on wetlands this week in South Korea.

Migratory birds traveling between Russia and Alaska in the north to New Zealand and Australia in the south congregate for often their only refueling stop at Yellow Sea tidal flats to feast on shellfish and other food.

South Korea, now one of the world’s largest economies, launched its reclamation project decades ago to increase its farm land when it was trying to rise from the ashes of the 1950-1953 Korean War and now says it will use the land for factories and recreation sites.

The study indicated that the critically endangered Spoon-billed Sandpiper and the endangered Spotted Greenshank were being pushed to extinction by the loss of wetlands.

“There have been large declines and some of this is irreversible,” said Nial Moores, a British-born conservationist and director of Birds Korea. “We anticipate the declines will not only continue but become more obvious in other species.”

South Korean environmental officials have said they thought there would be no major harm done to migratory birds because they would be able to find food at nearby wetlands in the country.

“The evidence very strongly indicates that most shorebird populations are declining in the Republic of Korea (South Korea), the study said.

The study said the loss of wetlands at Saemangeum has decreased water quality on the coast, which has led to a loss of marine life and puts other areas at risk.

The conservation groups who conducted the study through bird counts for three years are calling on the South Korean government to restore the tidal flow in the area by opening and enlarging the sluice gates.