location and climate have large effects on income levels and income growth through their effects on transport costs, disease burdens, and agricultural productivity, among other channels.
[not needed, but I'd like to add this~] Also, China's geography affects Asia's trading by blocking off certain parts of their trade. ... Also on certain parts the silk road would be through certain parts of the trade route. So on their way they could set up camp and grow their own crops. Europe would have a bit different route than the rest.