Nowhere Left to Retreat: Elephants, Trees and Capitals

In May, a herd of 15 wild Asian elephants continued their northern venture in  southwest China’s Yunnan Province after their year-long journey from their home in Xishuangbanna Yunnan.  Yunnan is th only area of China with wild Asian elephants. But for millennia, the habitat of wild Asian elephants stretched much farther north into China before human encroachment forced them south. 
An example of human impact on the environment is the widespread use of nanmu （楠木） wood in ancient Chinese architecture. By late 17th century, even Emperor Kangxi, who reigned during China’s longest period of prosperity, could not find a single nanmu tree for the biggest hall of his palace The Forbidden City.
Partly due to the ecological degradation in the once fertile Shaanxi area in the northwest, China's political, economic and cultural center shifted to the south since the end of the Tang dynasty in early 10th century. As a result, in late 14th century, Xi'an lost its chance of restoring its glory.