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19-07-2024

The 2024 shorebird survey in China: a myriad of threats

by He-Bo Peng

From March 22 to May 28, 2024, we conducted a survey of shorebirds and macrobenthos at 41 key stopover sites along the Chinese coast, sampled 2100 locations, collected 1200 videos of foraging birds. This is the tenth year of the project, making it especially significant for us. From the initial dozen research sites, we now cover nearly all major wetlands and bird habitats along the Chinese coast. We aim to understand the challenges faced by migratory birds in the East Asian-Australasian Flyway by starting with their most basic food sources.

A comprehensive survey of shorebirds and macrobenthos was conducted at 41 key stopover sites along the Chinese coast from March 22 to May 28, 2024.

In today’s Chinese coastal areas, the threat of mudflat loss has largely disappeared, with more threats now coming from other human activities. In what follows we give a brief illustrated overview of five prominent human interventions on mudflats, some of which appear rather benign for shorebirds (shellfish aquaculture), while others may constitute serious threats.

1. Intertidal shellfish aquaculture: As the most frequent and widespread human activity along the Chinese coast, shellfish farming on mudflats has multiple impacts on the macrobenthic organisms and birds. It can alter the biodiversity of macrobenthic organisms on the mudflats while providing abundant food sources for birds.

Oyster aquaculture in Southern China. The standing poles are concrete columns for oyster aquaculture, densely scattered across the mudflats, with little room for birds to land. The wooden huts built into the water in the distance are temporary accommodations for the fishermen while they manage the mudflats. March 25 in Hepu, Guangxi province.
Clam aquaculture in Southern China. The mudflats are divided into many small pieces belonging to different fishermen for aquaculture. Many fishermen manage their “farms” on the mudflats on a daily basis, such as cleaning up garbage, removing algae and, more importantly, preventing others from entering their farms. They also sometimes dig up Sipunculus on the mudflats as a tasty seafood. March 27 in Fangchenggang, Guangxi Province.
Shorebirds are feeding on shellfish-aquacultured mudflats. May 16 in Dalinghe, Liaoning Province.

2. Pollution: As the intertidal zone lies between the land and the sea and also receives water flows from rivers, intertidal mudflats are affected by pollution from lots of sources.

Baby shellfish hatchery on the beach, with outfall
pipes discharging directly into the sea. The sand beach is covered with white sewage pipes, and a steady stream of sewage is discharged from the hatcheries every day. April 11 in Raoping, Guangdong Province.
Mudflats bordered by a large petrochemical plant. In the foreground: Great knots feeding on the mudflats. It is not known how much direct impact chemical plants have on shorebirds, but pollution from chemical plants may lead to a rapid decline in macrobenthos that are food for shorebirds. May 13 in Panjin, Liaoning Province.

3. Invasive vegetation – cordgrass: This invasive plant was found along most of the Chinese coast but since 2023 China has conducted nationwide invasive plant eradication campaigns. As such many locations were cleared of smooth cordgrass. But it’s also growing back, and it will be a continued challenge to eradicate them in the long term.

Regrowing of smooth cordgrass along the coast of Jiangsu Province.
Cordgrass after removal with a lawnmower. The mowers can only cut the above-ground portion of the Cordgrass, but the below-ground portion of this invasive plant is so vigorous that subsequent tilling to a depth of 1 meter is required to kill the plant. May 23 in Diaokou, Shandong Province.

4. Bycatch: Bycatch only occurs very frequently along the coasts of Zhejiang and Fujian, and not much elsewhere. Nevertheless, such local problems can have flyway-scale consequences for certain species.

Great knot caught by fishing nets. April 21 in Wenling, Zhejiang Province.

5. Energy infrastructure: Windmills are all over the coast of China nowadays, but we have little to no knowledge about the impact of windmills on birds.

Windmills located in the mudflats. Shorebirds feed not far from the windmills; what kind of effect does the windmills have on the birds? We know very little. May 3 in Changyi, Shandong Province.

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