Currently, part of China's 'green wall’ (Northwest-North-Northeast Shelterbelt) is suffering from aging problem. As of now, the forest’s annual passing rate in Zhangbei town (northwest of Beijing) is 20%. If the situation deteriorates further, Beijing will lose its ecological shelter. From Anbound’s point of view, improving the air condition is the present focus of the local governments in Northern China; and thus, preserving and replanting the trees should be the priority. It is better to initiate responses than later as it may produce long-term impacts to Beijing.