Investigation of the sand sea with the tallest dunes on Earth: China's Badain Jaran Sand Sea

Abstract

China's Badain Jaran Sand Sea features the tallest dunes on Earth and a unique mega-dune–lake landscape. It had been explored little until the 1990s, though early scientific explorations surrounding the sand sea had begun by the early 20th century. Heated debates now focus on the desert environment, and particularly how the mega-dunes and desert lakes develop and evolve. This paper reviews the status of these debates and summarizes the supporting evidences. The environmental research mainly concerns formation and evolution of the sand sea, and its relationship with climate change. The proposed formation time ranges from the Early Pleistocene to the Holocene. Opinions vary about climate change on different time scales. The reconstructed climate change history is shorter than the sand sea's history, with the longest record extending to the Late Pleistocene. The mega-dune research focuses on sediments, dune morphology, and formation processes. It remains unclear whether the mega-dunes result primarily from wind action, control by the underlying topography, or groundwater maintenance. The sources of lake water are also debated, but there are four main hypotheses: atmospheric precipitation, groundwater from nearby areas, precipitation and snowmelt in remote areas such as the Qilian Mountains and the Qinghai–Tibetan Plateau, or paleowater that formed during past periods of wet climate. We believe that the sand sea deserves further study in terms of its dune geomorphology, evolution, and hydrology, and their responses to climate change. Meteorological and hydrological observations and monitoring in the sand sea are particularly necessary.

Introduction

Desert sand seas that are characterized by various sand dune types constitute an important part of the modern and ancient global environment (Lancaster, 1988). Though they are largely non-populated, sand seas can exert profound impacts on the lives of human beings. Expansion of sand seas has caused the decline and fall of ancient civilizations, and in modern times, has led to tragedies in areas such as the Sahel. With the development of modern technologies, the positive aspects of sand seas are also being recognized. Petroleum reserves in sand seas have been continually explored since the 1970s. Recent decades have also witnessed increasing interest in utilizing the rich sunshine resources in sand seas. For example, a new industry called “deserticulture” has been practiced in China since the 1990s to develop agriculture in desert sand seas and dune fields, supported by advanced technologies. These factors make it necessary to have a good understanding of the resources and environments of desert sand seas. However, to date, the harsh environments of sand seas have impeded research, making them among the most poorly understood global environments.

Sand seas and dune fields cover about 600,000 km² of the arid and semi-arid areas of China (Wang, 2003). They stretch from semi-arid zones with annual precipitation greater than 400 mm in the northeast to hyper-arid zones with annual precipitation less than 50 mm in the northwest. Combined with large differences in topography, these differences create a wide range of landscapes, resource potentials, and environmental, economic, and social significance in China's sand seas and dune fields. The Badain Jaran Sand Sea is the second-largest area of shifting sands in China (Wang, 2003). It is located at the northwestern edge of the region influenced by the East Asian Monsoon, near the lower reaches of the Heihe River, which is the second-largest endorheic river in China (Fig. 1). Because of the desert's large size, and its location upwind of many of China's most densely populated regions, it has become an area of increasing interest both to China's government and to researchers from around the world. What's more, Badain Jaran's unique characteristics, such as the tallest (up to 480 m) mega-dunes on Earth (Dong et al., 2009), the mysterious “booming sands”, and the long history of the regional Mongolian culture, have made it a central part of the Alxa Desert Geopark (Si, 2011).

Researchers have long been curious about the environmental evolution and geomorphic processes that have occurred in this sand sea, particularly where the mega-dunes are interspersed with the lakes that occur in many low-lying areas throughout the sand sea (Fig. 2) and that vary in size, shape, and salinity (Dong et al., 2004). The last decade has witnessed unprecedented interest in the sand sea by researchers, particularly in terms of the mechanisms responsible for the formation and evolution of the sand sea, of the mega-dunes, and of the desert lakes. However, many puzzles are far from being solved despite the great progress that has been made by researchers. On the contrary, debates over various aspects of the region are heating up as the research continues. The objective of this paper is to provide an overview of the research progress that has been made and of the status of the debates related to various aspects of the Badain Jaran Sand Sea, in the hope that this review will educate and intrigue researchers and that it will provide insights that will guide future studies.