Firstly, new inventions in medicine now enable us to cure most deadly diseases and people seem to live longer. 
Secondly, people don't know how to control population, especially in the countryside. They don't use any method of birth control and they don't know how to use it. Thirdly, thanks to the development of science and the help of technology, the birth rate is increasing. This is certainly a reason to be proud and happy but it is also a cause of overpopulation.