Years of wars in the north have left much of it deserted. The land in the south is more fertile and has a suitable climate, making it suitable for farming, especially for two crops.Desertification in the north had already begun to become serious in the Ming and Qing Dynasties. The south had a large population and a developed water network. Especially with the opening of the Beijing-Hangzhou Grand Canal, it was more convenient for the south to transport supplies to the capital.The Ming Dynasty partially opened up the maritime ban, while the Qing Dynasty had ports such as Guangzhou. In other words, the policy was relatively open.