Why was trade crucial to the survival of Ghana, Mali, and Songhai?

Trade is very crucial for the survival of Ghana and Mali does not have much resources, so they trade with other people. Some depend on food in exchange for what Ghana and Mali have to offer. Both countries are located close to the equator, but also has a lot of desert. Deserts provide no food, so they depend on other nations that grow food to supply them. Trade is also crucial for other nations too!

Trade was crucial to survive of Ghana, Mali and Songhai because it was the only way in that time to get resources because of the lack of them in their own land.

Explanation:

In Ghana, Mali and Songhai the possibility to get resources by their own is very poor, they have non-fertile lands, full of deserts, which couldn't provide food. In that time, to balance that lack of resources, trade between other nations were the best and almost only way to survive.