Hydrological change and human activity during Yuan–Ming Dynasties in the Loulan area, northwestern China

Abstract

Human activity on arid lands has been related to oases evolution. The ancient Loulan, an important transportation hub of the ancient Silk Road, developed on an ancient oasis on the west bank of the lake Lop Nur in Xinjiang, China. Previous studies and historical documents suggest that the region has experienced dramatic natural environmental and human activity–related changes over time, transitioning from a particularly prosperous oasis to a depopulated zone with harsh environment after about 1500 a BP (before present, where present = AD 1950). Based on systematic radiocarbon (14C) dating for natural plant remains and archeological sites in the Loulan area, it was revealed that the region re-experienced oasis environment from 1260 to 1450 cal. AD, corresponding to the Yuan–Ming Dynasties, which is the climate transition stage from the ‘Medieval Warm Period’ to the ‘Little Ice Age’, encompassing a series of pulse-like flood events which cannot be identified from lacustrine deposition due to the limits of sampling resolution and dating. It was found that humans re-occupied the Loulan area and built canals to irrigate farmlands during the period. The more habitable hydrological conditions that resulted from these environmental changes present one major reason for the re-emergence of human activities in the Loulan area.

The impact of climate change and human activity on the ecological status of Bosten Lake, NW China, revealed by a diatom record for the last 2000 years

“…The last 2000 years in Xinjiang, in arid northwest China, were marked by the flourishing of ancient civilizations, agricultural development, social progress, and increased climatic variability (Li et al, 2018; Mischke et al, 2017; Yang et al, 2009; Zhang et al, 2018). Historical documents and archeological investigations have revealed that the region is climatically sensitive and thus it provides the opportunity to investigate the relationship between human activity and environmental change during a period of high climatic variability (Mischke et al, 2017; Zhang et al, 2018).…”

“…The lake is currently eutrophic and considered to be at risk: the level of organic contamination in the water column and in the sediments is higher than that of other lakes surrounded by intensive industrial activity and located in developed countries (Shen et al, 2017). Over the last four decades, the region has experienced extreme hydrological changes in response to climatic warming, which has resulted in increased surface runoff and glacier recession in the surrounding mountains (Li et al, 2018; Wu et al, 2010; Yao et al, 2018). In addition, the area of Bosten Lake has decreased sharply over the last decade (2000–2016) (Tan et al, 2018).…”

“…In addition, during the past few decades, the lake has exceeded a critical threshold and entered a new state in response to the intensified human activity (Gong et al, 2017). Our understanding of the environmental responses in Xinjiang to human impacts over the last two centuries has increased substantially (Gong et al, 2017; Li et al, 2018; Wünnemann et al, 2006; Yao et al, 2018; Zhang et al, 2018), and in addition, the regional climatic record during the early and mid Holocene has been investigated (Huang et al, 2009; Zhang et al, 2006). Nevertheless, there are relatively few late-Holocene high-resolution paleoenvironmental records from the region, and it remains unclear whether human activity, climatic variability, or both are responsible for driving the changes in the trophic status, lake level, and salinity of Bosten Lake.…”

“…The late Holocene in Central Asia is characterized by pronounced climatic fluctuations: the warm/dry ‘Medieval Warm Period’ (MWP), the cold/humid ‘Little Ice Age’ (LIA), and the Current Warm Period (CWP). The MWP and the LIA are globally recognized as periods of pronounced climatic upheaval (Matthews-Bird et al, 2017), and in Central Asia increased precipitation variability occurred during the LIA (Li et al, 2018). Decadal-resolution climatic records from lake sediments, ice cores, and other archives show that moisture levels increased abruptly during the transitional phase between the MWP and the LIA (from AD 1260 to 1450) (Yang et al, 2009; Zhang et al, 2018).…”

“…Decadal-resolution climatic records from lake sediments, ice cores, and other archives show that moisture levels increased abruptly during the transitional phase between the MWP and the LIA (from AD 1260 to 1450) (Yang et al, 2009; Zhang et al, 2018). Decreasing temperature, resulting from a reduction of regional evaporation and wetter conditions, marked the MWP/LIA transition (Chen et al, 2006; Li et al, 2018). Other paleoclimatic records from Central Asia show that precipitation levels increased between AD 1260 and 1450, peaking during the LIA (Chen et al, 2015; Yang et al, 2009).…”