THE RETURN TO NATURAL CONDITIONS 



Slowness of Return to Normal Conditions 



Before passing to consider another topic, I should like to call 

 attention specifically to the fact that a stream area from which 

 natural life has been eliminated by pollution is extremely slow in 

 recovery. In the questionnaire which was sent the game protectors, 

 discussed elsewhere in this paper, they were asked, among other 

 things, how long it took an area that had been adversely 

 affected by pollution to become restored to normal conditions, 

 and a number of them said in response to this question that the 

 stream was never restored. This is the careful judgment of 

 men trained to outdoor life and accustomed to observe stream 

 conditions and to follow changes in them from year to year. 

 Perhaps it would be wrong to accept this statement in an absolute 

 and mathematical sense, but we shall not go far astray in taking it 

 to be generally true. Once the life of a stream has been wiped out, 

 the process of recovery demands a very long period of time, if, 

 indeed, the stream is ever restored. Of course, no start can be made 

 until the causes for the destruction of the aquatic life have been 

 removed, and thereafter the restoration of normal conditions depends 

 upon a series of factors that it is not difficult to outline in general, but 

 impracticable to calculate in definite fashion. It is evident, without 

 further argument, that the longer the pollution has been going on, 

 the farther it has extended, the greater the area of the water in- 

 volved, and the larger the amount of deleterious substances that have 

 accumulated, the longer it will take for those changes to be carried 

 out that will eliminate the poisonous substances and restore the 

 bottom and the water to a condition in which life is possible again. 

 Repopulation of the area will naturally be brought about by the 

 migration of animals of various sorts from contiguous territory 

 into the restored region, and, of course, also, by the planting of such 

 organisms as may be introduced designedly in an effort to replenish 

 the life of the water. Ordinarily, men have not attempted to do 

 more than to plant fish, and usually have introduced them in young 

 stages. It is, of course, worse than useless to do this until the food 

 supply has been provided in one way or another, and any failure 

 to consider this aspect of the question merely means that the fish 

 which were introduced would starve to death and the experiment 



