Impact of coastal island restoration engineering and subsequent tourism on migratory waterbirds: a 3‐year case from Southern China

Abstract

Coastal engineering poses a significant threat to the survival of migratory waterbirds worldwide. However, the mechanisms through which engineering affects waterbirds are still unclear. To gain a better understanding of this issue, we conducted a three‐year survey of waterbirds on Shanxinsha Island, which underwent restoration engineering, along the East Asian–Australasian Flyway. We compared the seasonal migratory change among different species groups through and after the island restoration engineering. We observed a total monthly maximum count of 118,506 individuals from 61 waterbird species over the span of 38 months, including eight globally threatened species and five species that exceeded 1% of the flyway population. Throughout the survey periods, the average number of total waterbirds and small shorebirds observed during the migrating season decreased by 52.7 and 48.6%, respectively. The massive loss of high‐tide roosting areas was the primary factor contributing to this decline. The combined effects of increased vegetation and deeper water levels resulted in a 38.8% reduction in exposed tidal flat area, as determined through land cover verification and fractional vegetation cover calculations. While tourism activities exhibited fewer negative consequences compared to island restoration engineering, they had a greater impact on small breeding shorebirds. Our study showed that small shorebirds were particularly susceptible to island restoration engineering, whereas large shorebirds and swimming birds were more flexible in their use of roosting or foraging sites. We suggest that the impact of future coastal engineering requires more detailed assessment and monitoring, especially for small migratory shorebirds.