How can droughts be triggered by physical (natural) conditions in agriculture droughts

Arid and semiarid subcategories are part of which climate

Can someone me? i need to have this done as soon as possible! i'm putting 20 points on this!

How have ethnic groups shaped the population in central america and the caribbean? how has migration shaped the population in central america and the caribbean? how has small land areas shaped population in central america and the caribbean? how has a rapid population growth shaped the population in central america and the caribbean?