486 ECOLOGY AND WILD LIFE CONSERVATION 



prickly pear, and several other useless thorny plants to increase. Un- 

 desirable rodents, such as kangaroo rats, prairie dogs, ground squirrels, 

 and wood rats, increase in abundance under these conditions ; but deer, 

 antelope, and sage grouse become scarce. On the other hand, if graz- 

 ing cattle are reduced to a point where the valuable perennial grasses 

 can survive, the cattleman not only harvests better beef ; but the un- 

 desirable rodents are reduced in number and more valuable wild life 

 returns. 



The practice of burning pasture land and wood lots in many states 

 also has undesirable results. The burning destroys valuable humus as 

 well as removing the cover so necessary for survival of valuable game 

 and insectivorous birds. Pernicious weeds take over and become more 

 abundant when the land is burned often. The only bird which becomes 

 more common is the crow, which in large flocks may become an annoy- 

 ing pest. Hawks and foxes easily catch most of the game which has 

 no place to hide, and prairie dogs, ground hogs, and other rodents take 

 over. Every time a farmer burns off a crop of weeds rather than 

 turning them under with the plow, he has destroyed many dollars' worth 

 of fertilizer per acre. 



To summarize, we have found that the ecologist has learned princi- 

 ples that are of vital importance to man if he is to conserve his natural 

 resources. The web of life is very complex, and the balance of nature 

 can be maintained only by preserving all sorts of animals including the 

 predators. When man upsets this balance, the results may be disastrous 

 not only to wild life but to human health and society. In recent years 

 the wild life ecologist has restored both small and big game far beyond 

 the hopes of the most ardent conservationist. One of the most im- 

 portant problems today is to educate the farmer and the stockman to 

 recognize that wise practices will benefit both them and wild life. 



REVIEW QUESTIONS 



1. Define ecology. 



2. What are some fields where ecological principles have been applied? 



3. What are some methods of preventing erosion on sloping land? 



4. Describe steps by which a bare ledge becomes a rich forest and compare 

 with the changes from a shallow lake to a forest. 



5. Describe the biome in which you live. 



6. Trace the food chains for the kinds of flesh you have eaten in the past month 

 so far as is possible. 



7. How does man upset the balance of nature ? 



8. Trace the development of game laws for the protection of wild life. 



9. How have the Pittman-Robertson Act and the Dingell Act increased your 

 possibilities for recreation? 



10. What is meant by harvesting the surplus of wild life? Explain how it 

 works on beaver and deer. 



