The highly population country ^cause n effect^

Mdm. Thong want me searching about the highly populated country bring whats effect to the government.At first,my mind think something which related to China.China is an example of the highly populated country.Latest,many product made in China bring lots effect to whom consumed.For instance, Sanlu formula milk n egg made by some stupid people.These food actually make our body worst .Migration from town to city increase force government take measures to prevent it grown enormous ."One couple one child",bandwagons of birth control n so on.Why we need to prevent it ?This is because shortage of food , environment pollution ,case of crimal increase......So , I need to write an essay to teacher.Bye2