History of the Great Wall of China the three, China's chief concern since the earliest times had been Mongolia – the home of many of the country's fiercest enemies including the Xiongnu, the Xianbei, the Khitans, and the Mongols. The Gobi Desert, which accounts for two-thirds of Mongolia's area, divided the main northern and southern grazing lands and pushed the pastoral nomads to the fringes of the steppe. On the southern side (Inner Mongolia), this pressure brought the nomads into contact with China. For the most part, barring intermittent passes and valleys (the major one being the corridor through Zhangjiakou and the Juyong Pass), the North China
Gobi Desert taxes on the revenues it derives from the mine (an agreement was reached whereby the operation will be exempt from windfall tax. The Gobi Desert is expanding at an alarming rate, in a process known as desertification. The expansion is particularly rapid on the southern edge into China, which has seen of grassland overtaken every year by the Gobi Desert. Dust storms, which used to occur regularly in China, have increased in frequency in the past 20 years, mainly due to desertification. They have caused further damage to China's agriculture economy. The northern and eastern boundaries between desert and grassland