CHAPTER 29 • THE BALANCE OF LIFE 



1 If living things are in balance, how can the population of any 



species increase? 



2 Why are there more insects or fish in some years than in others? 



3 How can a species thrive as well in a strange region as it does in 



its natural or original home? 



4 Does introducing a new species into a region always cause harm 



to others? 



5 Does any harm result from exterminating any species? 



6 How have some species been exterminated? 



7 Can species change their feeding or other habits to fit a new set 



of conditions? 



8 Are there any regions that once had much Ufe but now have 



little — or vice versa? 



9 Does increasing the amount of life in one region have to reduce 



the amount in another? 

 10 Does growth of human population mean that other species are 

 reduced in numbers? 



We keep a young child away from complicated machinery because there is 

 danger he might get hurt poking among the moving parts which he does not 

 understand. Another reason is he might injure the machinery, or start some- 

 thing that might lead to even greater disaster. When we poke about in this 

 complicated world of plants and animals, we are not always aware that we may 

 be starting trouble. Shooting blackbirds for fun may mean merely shooting 

 blackbirds. But it may mean advancing the price of bread in far-away cities 

 next autumn. For while each hunter may kill only a few birds, the sport may 

 turn the scales between locusts and wheat. Neither the hunter nor the house- 

 keeper buying bread far away may know what birds here have to do with the 

 price of bread there. 



Living for generations in a particular locality, people learn pretty well 

 what plants and animals they can afford to encourage or to destroy. As we 

 move rapidly into strange regions, the task of maintaining a balance of 

 Hfe becomes increasingly difficult. This is not so much because the problem 

 becomes more complex, for we can construct and operate very complex 

 machinery: we can learn which lever or button to press for desired results. 

 But when man interferes with natural processes, he cannot always be sure 

 what he is setting loose or what he is bringing on. And yet we have to in- 

 terfere. Living means interfering with nature. Is it possible to upset the 

 balance without bringing about undesirable results? How can we tell how far 

 it is safe to go? 



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