One way to see if a place is "poor" or "rich" is to see how well they have preserved their most valuable things.  If a people are poor, they have to sell the family heirlooms.  The most valuable things on the planet are:  the arable land, the healthy rivers and ecosystems, the biodiversity.  These are without a doubt the gems which are not a fad but are irreplaceable.  Some places on the earth have turned themselves into deserts such as the midwest USA, deforested, killed the river dolphins, etc,  different problems all over.  Looking at the map, it appears that much of Africa has had the wherewithal to not destroy itself with industrialization and suburbatardation.  In this regard, I see the African continent as perhaps the wealthiest on the planet.