6) which statement best describes the effects of drought, desertification, and erosion on the people who live in the sahel on the edge of the sahara desert? a) these factors have led to warfare between tribes in the region. b) these factors have caused a great migration of people from the region. c) these factors have caused the united nations to declare the region endangered. d) these factors have led to hunger in the region because of a lack of arable land.