Question

there was a population explosion during the late 20 century what were the reason for this

Answer 1

The most important cause of famine is therefore not thepopulation explosion. Famine is primarily a consequence of unequal distribution of food, which in turn is caused by social-economic inequality, lack of democracy and (civil) war. ... As mentioned, poverty is also an underlying cause of rapidpopulation growth.

Answer 2

due to the decrease of death rate compared to the birth rate