Human drivers accelerated the advance of Pearl River deltaic shoreline in the past 7500 years

Abstract

In order to examine the role of human drivers in shoreline advance of the Pearl River delta plain over the past 7500 years, this study reconstructed several palaeo-shorelines based on sedimentary records, archaeological findings, historical archives, family ancestral books and modern survey data. With these shorelines, this study quantified the land growth rate for each of seven time periods spanning from the Neolithic-Bronze Ages, through the agricultural period, to the modern industrial era. The results show that, since c. 7500 cal. a BP as the sea level ceased to function as the primary driver, fluvial discharge and tide became the main natural drivers. Between 5500 BCE and 200 BCE, as fluvial discharge was progressively reduced, the amount of sediment drained out to the sea by tidal action was also progressively reduced due to the decrease of the estuarine space. As a result, the land growth rate was kept around 0.36–0.38 km2/a for this period. During the agricultural stage between 200 BCE and 1950 CE, human activity has led to a continuous increase of land growth rate, from 0.78 km2/a caused by land clearance (200 BCE to 960 CE) to 2.69 km2/a triggered by early land reclamation (960–1370 CE) and further to 4.50 km2/a as more advanced techniques were used (1370–1950 CE). Finally, a better organization of human power in land reclamation and the use of machinery since 1950 CE has accelerated the land growth to an average of 10.56 km2/a. The river damming and soil preservation projects in the past three decades have greatly reduced sediment supply and caused a significant slowdown in the shoreline advance.