The population growth rate of human beings is quite worrying. Towns, streets, and schools have been overcrowded due to rapid population growth. For instance, by 1960 the earth harboured a population of 3 billion people. However, by 2010 the population had doubled. The reasons are crystal clear. Increased immigration and birth rates, and a decline in the rate of mortality, are evident causes of overpopulation. When the number of people surpasses the carrying capacity of a particular area, overpopulation occurs. We all know that resources are usually limited. ("Human Overpopulation Causes, Effects, and Solutions")