Answer:
because they don't have much resources and must trade to get resources(i think, this is a guess)
Step-by-step explanation:
i searched this and put the answer here because i didn't know what to put here..
Google's Answer
Explanation: 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. ... Deserts provide no food, so they depend on other nations that grow food to supply them.