Due to overpopulation:-
1)pressure on the country to feed the population.
2)deforestation on a large scale to provide space for housing
3) water shortage occurs cause there is hardly any groundwater recharge in this present age
4)since there are more number of meat-bags ,lot of Carbon dioxide is released leading to imbalance in oxygen and carbon dioxide level
5)since there are many people the government faces underemployment and sometimes no employment at all. So there results a lot of waste of space on that country.(no offence)
6)more the people- more the automobiles. so you can expect how clean the air will be.
7)miscellaneous problems like improper drainage, water management, placing of houses for people, etc....
8)more the people- more the production of waste. so the country would obviously be dirty
9) rate of consumption of all the types of goods increases like-vegetables, fuel, oil, etc
10)sometimes overcrouding cause improper sanitation problems that may lead to serious health issues
11)some time it also leads to wars and conflicts for the sake of province..........