Millet is grown in the Sahel because it is one of the main staples of the people there. Also, when grown with cowpea and sorghum, the risk of complete crop failure is greatly reduce
Erosion takes away material and sediment from the beach whereas deposition puts more sediment onto the beach
Nitrogen and oxygen are the main constituents of the atmosphere plus water vapour near the surface. Carbon dioxide is present in smaller amounts butgl of course it can have a profound influence on the climate as global warming has shown, Greenhouse gases include water vapour, carbon dioxide, methane and nitrous oxide.
