Increasing terrigenous pollen input in the late Holocene: Indications of intensive human activity and accelerated delta plain progradation

Abstract

Rapid expansion of the Pearl River Delta Plain (PRDP) of South China in recent millennia has been attributed to climatic changes or human impact. We have addressed this issue through detailed examination of pollen, charcoal, organic matter, chemical elements and foraminifera in a 6.5 ka marine core SCSF47 in the continental shelf of the northern South China Sea. Our results reveal a sharp acceleration in terrestrial sediment input around 2.8 ka BP connected to dramatic increases in pollen concentration, total organic carbon, and charcoal. These increases, combined with results of analysis of surface pollen samples in the area, indicate that the Pearl River's influence strengthened. The main source of pollen changed from the Pearl River basin to the PRDP during this time, indicating accelerated formation of the PRDP. Moreover, significant increases in charcoal concentration and Pinus pollen indicate that human activities intensified in this area during the past 2.8 ka, implying that human activities accelerated development of the PRDP. Our study provides evidence that the PRDP's accelerated formation in the late Holocene was mostly due to human activities, as the precipitation and other climatic variables have not changed much during this period. The findings suggest that ongoing global warming and human activities may substantially affect deltas and facilitate predictions of deltas' responses to such drivers.