11 Feb 2016

Reclamation of Yellow Sea causing serious declines in migratory shorebirds

The main threat to the globally threatened Great Knot is reclamation in the Yellow Sea (image (c) Zhang Ming)
By James Lowen

In-depth studies have indicated that rapid declines in three species of shorebird that migrate between Siberia and Australia is due to land reclamation along China's Yellow Sea coastline.

Research published in the Journal of Applied Ecology has revealed 20% reductions in the survival of three shorebirds that use Yellow Sea mudflats to refuel while migrating along the East Asian—Australasian Flyway. The three species – Red Knot Calidris canutus, Great Knot Calidris tenuirostris and Bar-tailed Godwit Limosa lapponica – nest in different areas of north-east Siberia but rely on staging posts in the Yellow Sea before wintering together in Western Australia. 

By individually marking thousands of birds with colour rings, an international team of scientists calculated the annual and seasonal survival of the three species from 2006– 2013. They found that the birds' survival rates remained constant on breeding and wintering grounds, but declined markedly from 2010 onwards during and immediately after each migration.

Led by Professor Theunis Piersma (Royal Netherlands Insitute for Sea Research), the team concluded that the declines stemmed from the loss of habitat and food on Yellow Sea mudflats – a result of land reclamation. Between 1990 and 2013, the area of shallow seas and intertidal flats along the Yellow Sea shrank by an average of 4% per year, with the rate of loss doubling towards the end of the period.

"This research", says Piersma, "delivers proof that land reclamation around the Yellow Sea puts many migratory birds at risk". Piersma fears that continuing land reclamation will result in "a further halving of the shorebirds' populations within three to four years. To halt further losses, the clearance of coastal intertidal habitat must stop now".

"Shorebird populations worldwide are declining and their habitats are under stress from human factors including land-use change, but the loss of habitat in the Yellow sea is particularly alarming, " said Ade Long at BirdLife International. 

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Migratory Bar-tailed Godwits roosting on an active dredge-dumping site on the Yellow Sea on 20 April 2012 (David S. Melville). The material was being excavated from a channel to improve access to the Donggang Fishing Port, Liaoning Province. The infilled area is planned to be part of an industrial park to be built on an area of intertidal mudflat that was excised from the Yalujiang National Nature Reserve by a boundary adjustment in 2012.

BirdLife International, in its role as Red List Authority for birds for the IUCN Red List, listed all three of these species to higher threat categories in 2015, partly owing to information about their declining population on the East Asian-AustalasianFlyway.

Professor Theunis Piersma is also a professor in Global Flyway Ecology at the University of Groningen, a position funded by Vogelbescherming Nederland (VBN, BirdLife in the Netherlands) and WWF-Netherlands. Professor Piersma and his team are part of the Global Flyway Network, a global alliance of worldwide shorebird-research groups. In 2014, he was awarded the Spinoza Prize – the so-called ‘Dutch Nobel Prize’ for his work on migratory shorebirds. Click here to read an interview with Theunis Piersma in the magazine World Birdwatch.