Anthropogenic environmental evolution of ganggeng lake in the East Asian monsoon marginal zone over the past century

Abstract

Over the past century, there has been persistent controversy regarding the relative impact of climate change and human activities on the evolution of the lake basin critical zone in the East Asian monsoon marginal zone. In this study, we focused on Ganggeng Lake, situated in the East Asian monsoon marginal zone, to conduct a comprehensive analysis of sedimentation rates, magnetic susceptibility, grain size, and pollen data from sediment cores, providing valuable insights into the sedimentary environmental changes and regional vegetation dynamics over the last 150 years. The results revealed that around the 1960s, the implementation of the government's “Take Grain as the Key Link” policy resulted in a substantial increase in water usage for extensive irrigation on cultivated land. Consequently, the inflow into the lake declined, weakening basin erosion and reducing sediment flux, leading to distinct changes in the physicochemical characteristics of the Ganggeng Lake sediments. Additionally, the pollen assemblages provided valuable information on the vegetation changes in the Ganggeng Lake basin over the past century. Notably, two significant shifts in the vegetation community were observed, corresponding to the impacts of two crucial national policies: the “Take Grain as the Key Link” policy in the 1960s and the “Conversion of Cropland to Forest” policy around 2000. The implementation of ecological environmental protection projects played a vital role in promoting the recovery of vegetation and enhancing ecosystem functionality within the lake basin. Based on our findings, it appears that over the past few decades, human activities may have exerted a more pronounced influence on the lake basin critical zone in the East Asian monsoon marginal zone than climate change.