Abstract
Based on three ornithogenic sediment profiles and seabird subfossils therein from the Xisha Islands, South China Sea, the relative population size of seabirds over the past 1000 years was reconstructed using reflectance spectrum. Here we present an apparent increase and subsequent decline of seabirds on these islands in the South China Sea. Seabird populations peaked during the Little Ice Age (LIA, 1400–1850 AD), implying that the cool climate during the LIA appears to have been more favorable to seabirds on the Xisha Islands in the South China Sea. Climate change partly explains the recent decrease in seabird populations over the past 150 years, but the significant decline and almost complete disappearance thereof on most of the Xisha Islands is probably attributable to human disturbance. Our study reveals the increasing impact of anthropogenic activities on seabird population in recent times.
Highlights
Based on three ornithogenic sediment profiles and seabird subfossils therein from the Xisha Islands, South China Sea, the relative population size of seabirds over the past 1000 years was reconstructed using reflectance spectrum
Seabirds play a central role in the dynamics of these coral island ecosystems, and studies of their ecology in the South China Sea will contribute to a greater understanding of the development of tropical insular ecosystems[11]
A constant initial concentration (CIC) model was used to calculate 210Pb dates for profiles BD1 and ZS2, and a constant rate supply (CRS) model was employed for the age calculation of profile CH20
Summary
Based on three ornithogenic sediment profiles and seabird subfossils therein from the Xisha Islands, South China Sea, the relative population size of seabirds over the past 1000 years was reconstructed using reflectance spectrum. Seabirds forage at sea and breed on land, delivering significant quantities of marine-derived nutrients and contaminants to terrestrial ecosystems[1] Activities of seabirds such as Little Auks and Northern Fulmars in the Arctic resulted in the accumulation of guano, and significantly impacted on the properties of soil and lacustrine sediments, as well as plant communities[2,3,4]. The Xisha Archipelago (Fig. 1) is a group of coral islands located in the central South China Sea, and was formed during the mid-late Holocene[9] (last ~5000 years). This is approximately 10% of the world population for this species, rendering it the largest habitat for Red-footed Boobies in the Pacific and second largest in the world[16] Plants on these islands, including shrubs and trees, in addition to sand grounds, provide habitats for those birds[17]. Those materials provide specific insights into seabird ecology over the past 1000 years
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