Earth:Mu Us Sandyland

The Mu Us Sandy Land (also known as the Maowusu Desert; 毛乌素沙漠/毛烏素沙漠 Máowūsù Shāmò or 毛乌素沙地/毛烏素沙地Máowūsù Shādì) is a desert in Central China. It is crossed by the Great Wall of China at the south-eastern end of the desert. The Mu Us Sandy Land forms the southern portion of the Ordos Desert and part of the Ordos Loop. The Wuding River drains the area, and then flows into the Yellow River.

Delineation

Confusion exists about where the Ordos Desert begins and where the Mu Us Sandy Land ends. The northern portion of the Ordos Desert goes by another name—for example, a map in Julia Lovell's book The Great Wall: China Against the World 1000 BC–2000 AD shows the Ordos Desert only in the portion of Inner Mongolia, which lies south of the Yellow River. Several research papers cited below claim that the Mu Us Sandy Land includes part of Shaanxi and Gansu. A clear delineation of the area is still needed here, based on multiple sources.

The Mu Us Sandy Land of north central China lies at 37°30'–39°20'N,107°20'–111°30'E and covers 40,000 km². As part of the Ordos Plateau, the elevation ranges from 1,000m to 1,300m (as low as 950m in some south-eastern valleys, and reaching between 1,400m to 1,600m in the north-western area). It is the only one of China's twelve sandy zones that is in the transition between a typical steppe and desert climate. The semi-arid continental climate subjects the soil to wind erosion.

Geology

As noted above, the Mu Us Sandy Land forms part of Ordos Plateau and includes part of the Loess Plateau alluvial plain with a concave floor. Exposed sands in the area come from Cretaceous red and grey sandstone. Quaternary sediments include a variety of sand types which are easily moved by the wind. In the south of the Great Wall (see below), sand dunes become more frequent due to damaged vegetation caused mostly by moving sand.

History

Research in the Salawusu River Area in 1978 delineated the strata of the Salawusu River in the area of the Mu Us Sandy Land. This suggests that the prehistoric climate was mild and wet with numerous rivers and lakes, yet limited plant life and wildlife in the early stage of the Late Pleistocene age. The climate became dry and cold while eolian sand began to accumulate in the later stage of the Late Pleistocene age. The climate changed again to mild and wet early in the Holocene Epoch as lakes with marsh sediments formed. Later, the climate changed back to dry and cold, allowing a semi-arid steppe landscape to form. These climatic fluctuations were caused by the glacial and interglacial periods of the Northern Hemisphere. The Mu Us Sandy Land underwent a series of changes, including the formation shifting sands as well as the fixation and reduction of dunes.

Economy

As early as 218 BCE, grazing was the main way of life for local people. The Mu Us Sandy Land lies in a transition zone where areas of both pastoral land and farmland co-exist.

Based on remote sensing data, rangeland has experienced an increase in both total biomass and number of grazing animals. Active measures which have been taken to limit desertification have resulted in increased vegetation cover and lowered potential for wind erosion. The increase in biomass resulted in an increase in both grazing and farmland production. The area under cultivation increased fivefold from 1978 to 1996. The grasslands seem to be thriving under the current high levels of grazing pressure.

Desertification

A 2002 study of desertification in the Mu Us Sandy Land defined the area as an agro-pastoral transitional zone in northern China. During a 35-year period from the 1950s to the 1990s, its landscapes changed significantly. In most of the sandy land, desertification developed rapidly, while marginal areas in the east and south were restored to some extent. By the late 1990s, shifting and semi-fixed sandy lands covered 45% and 21% of the Mu Us Sandy Land, while fixed sandy land decreased by 7.2% of the entire sandy land. Desertification was much more severe in the middle and north-west pasture land areas than in the eastern and southern areas of farmland and pasture. Overuse, overgrazing, and overcutting have been the main causes of desertification.

To rehabilitate desertified land, Dong, et al. recommended abandoning unsustainable land management practices in 1982, referring to them as "the current irrational human activities" and gaining a better understanding of how climatic change affects the natural environment. Those writers suggested that the human activities must be carefully managed to meet both human and environmental needs.

Ecological Restoration

After 1949, the Chinese government carried out a variety of ecological restoration projects including sand stabilization, irrigation development, afforestation, soil improvement, and transformation of the desert with remarkable results.

The Great Wall

As early as 453 BCE, the Yiju people built a double wall in the southern region of the Mu Us Sandy Land to protect themselves against the northernmost Chinese states. Of these states, the Quin were especially threatening, although the Qin Dynasty also are reported to have done wall building in the area. Later in history, the Quin dominated all of this area and built walls. In 129 BCE, the Han Dynasty gained control of the area and strengthened the walls although they were still fighting to maintain control in AD 45. Much later, the Ming Dynasty portion of the Great Wall crossed the area.