There are two main reasons for this 9. THE UPS AND DOWNS OF effect. One is that, with the rapid growth POPULATION GROWTH of population, people need more and more land to grow crops, to build houses to live ND DOW'NS OF POPULATION GINWTH in. As a result, there is less and less land and space for the wildlife. Another impor- tant reason lies in the fact that a host of newly built factories constantly discharge harmful gases and liquids, which heavily pollute the environment. This pollution, together with other factors, has resulted in serious ecological problem. All these As is clearly shown by the two have made it more and more difficult for graphs, since 1800, with the rapid the wildlife to survive. Therefore, the growth of the U. S. population, the num- population increases while more and more ber of species of wildlife no longer existing species of wildlife become extinct. shot up, adding up to 70 in 1900. Obvi- To solve the problem mentioned ously, the population explosion resulted in above, I suggest that the government should take some strong and effective the sharp decline of wildlife in this country. measures such as heightening people's 20 21