the ups and downs of population growth As is seen from the two graphs,it is clear that with the rapid growth of U.S.population from 1800 to 1990,the number of its wildlife species no longer existing soared during the same period.Naturally,we can draw the conclusion that the sharp decline of wildlife species resulted from the population growth.Two reasons may account for this phenomenon.To begin with,as the population grows,people consume much more natural resources,which often leads to excessive hunting.Second,with the increase of human activities,modern people take up more and more space.Which has a great impact on other species.Finally,the problem of pollution becomes more and more serious with the development of modern industry.More and more animals have to adapt themselves to the decaying environment or move to a totally different place,but not all of them are fortunate enough to survive the changes.Solving this problem calls for,above all,the government’s efforts to control population growth,to decrease industrial pollution and to enhance the laws to forbid wildlife hunting.Moreover,common citizens should be aware of this ecological crisis and take on the responsibility of wildlife protection.In a word,only when the government and the common people make joint e f forts can we hope to find a satisfactory solution to this problem.