Chinanews, Lanzhou, July 14 – Gansu Provincial Cultural Heritage Administration and Gansu Mapping and Surveying Bureau have jointly sent 4 research teams to conduct on-the-spot investigation of the Gansu section of the Great Wall.The investigation will be completed in the next 2 years, covering the Great Wall parts built in the Ming Dynasty (1368 – 1644), Han Dynasty (206 BC – AD 220) and the Warring States Period (475 – 221 BC). The Gansu Section of the Great Wall is about 5,000 km long. Part of it is located in the Tibetan-inhabited areas.The Gansu section of the Great Wall located on the west side of the Yellow River is faced with the threat of wind erosion, while the part located on the east side of the river might be eroded by rain, flood, rats or ants.However, human activity is perhaps the most dangerous to the protection of the Great Wall, said Yang Huifu, the director of Gansu Institute of Archeology. Besides, over the decades local government has done nothing to protect the Great Wall.