High-frequency mangrove degradation events during the Holocene climatic optimum in the Maowei Sea of tropical China

Abstract

Mangrove forests are ecologically and economically significant ecosystems in the (sub)tropics, and it is important to reconstruct their historical changes to understand the future of mangrove forests in the context of global warming. Although the Holocene climatic optimum (HCO) is regarded as an analogue of future climatic change, high-resolution studies of mangrove ecosystem changes during this period are rare. This study presents a high-resolution sedimentary record for the HCO (7800–6900 cal. yr BP) in the Maowei Sea, northern Beibu Gulf, China. Contributions of mangrove-derived organic matter in the sediments were quantified using an end-member mixing model and a Monte Carlo simulation. The model reveals there were high-frequency degradation events (11 times) of the mangrove forests during 7800–6900 cal. yr BP. Palaeo-environmental records (e.g., sea-level, stalagmite δ18O values, and sediment Ti contents) from near the study area demonstrate that an intensified Asian winter monsoon (AWM), rather than sea-level changes, was the key factor responsible for the high-frequency mangrove degradation events during the HCO in this region. The results indicate that the effects of the intensified winter monsoon on tropical ecosystems may be greater than previously thought, particularly in the context of anthropogenic warming scenarios.