How have the Sahara and the tropical rain forest affected trade development within Africa

The Sahara and the tropical rainforest affected trade development within Africa in several ways. Sahara, being a desert, made the connection very difficult, because every trip should have been planned with careful precision in order o avoid loss of water. Tropical rainforest, on the other hand, made connection difficult because it was necessary to cut out a massive portion of the forest, that would make inestimable damage to one of the latest rainforest.