The utilization of a natural levee − backswamp landscape by late Neolithic communities in the coastal lowlands of East China

The coastal lowlands of eastern China served as important centers for Neolithic wetland rice agriculture. However, there is limited understanding as to how ancient communities mitigated coastal flooding and saltwater intrusion to safeguard rice production. In this study, three sedimentary profiles were collected from a late Neolithic site in the lowlands of coastal East China and subject to multi-proxy analyses including determination of chronology, total organic carbon content, and sporo-pollen analysis to reconstruct the geomorphological and ecological environmental evolution since 6.3 cal. kyr BP. These analyses reveal how Neolithic communities utilized the tidal river landscape across a bayhead delta plain, and indicate that, by 5.9 cal. kyr BP, a tidal river–natural levee–backswamp geomorphic system had developed, with rice cultivation initiated soon after the formation of this landscape. Exploitation in the backswamp intensified between 5.3 and 5.0 cal. kyr BP, resulting in a marked increase in rice productivity, a situation that contrasts sharply with evidence observed at piedmont sites along the Hangzhou Bay coast, where saltwater intrusions were associated with a marked decline in rice yields. Our findings suggest that the late Hemudu communities occupying the bayhead delta plain successfully mitigated coastal flooding and the effects of saline intrusions, thereby ensuring continued stable rice production through the strategic utilization and maintenance of natural levee systems. This study highlights the sophisticated environmental management practices of Neolithic societies in coastal lowlands adopted against a background of environmental deterioration, and offers new insights into the development of wetland rice agriculture in East China.