NATURALIST'S GUIDE TO THE AMERICAS 



While the burning over of land may be 

 the only practical method of cleaning 

 it under some circumstances, it should 

 be recognized that this involves a re- 

 duction in the future fertility of the 

 soil and is a method to be avoided so 

 far as possible. Unless scattering of 

 brush is necessary to prevent drying 

 out of the soil or to favor reproduction 

 it should be collected in piles and burned 

 in the late fall or winter. Railroads in 

 timbered country, operators of portable 

 saw mills and men using power logging 

 should be induced to adopt such safe- 

 guards as would prevent the occurrence 

 of fires or restrict the damage caused by 

 those which may occur from their 

 negligence. If necessary the aid of the 

 law should be invoked to these ends. 

 In conclusion, attention should be 

 called to the desirability of careful in- 

 vestigations on the precise changes in 

 the ecological conditions due to fires in 

 various types of habitat; to the need of 

 exact quantitative as well as qualitative 

 studies on succession in such habitats; 

 and especially to the almost untouched 

 field afforded by studies upon the fauna 

 in these tracts. Every student of 

 ecology who has available for study a 

 burned over area has in it an opportunity 

 which should not be neglected. 



10. THE EFFECT OF POLLUTION ON 

 ANIMAL LIFE* 



BY FRANK COLLINS BAKER 



Stream pollution may be broadly 

 divided into two main divisions: con- 

 tamination by organic sewage from 

 cities and towns and by chemical wastes 

 from factories and mines. Both are 

 inimical to life but the latter is espe- 

 cially fatal to animal life, causing wide 

 stretches of otherwise fertile streams 

 to become veritable deserts. Organic 

 sewage, in a crude or highly concen- 

 trated form, is also very injurious, 

 effectually eliminating most forms of 

 life from the polluted body of water. 



1 The greater part of this topic is condensed from 

 a paper read before the Illinois State Academy of 

 Science, and published in Vol. XIII, of the T.rans- 

 actions of that Society, pp. 271-279, 1920. 



The importance and seriousness of 

 the problem of stream pollution in its 

 effect on the life of the rivers and 

 streams into which the contaminating 

 material is discharged has not, until 

 very recently, been given the attention 

 the subject demands. The diminishing 

 fish supply, and in many places the 

 very objectionable physical character 

 of the polluted waters, have caused the 

 authorities of several states to pass 

 laws governing the discharge of these 

 wastes into streams and the establish- 

 ment of penalties for disregarding these 

 laws. New York and Massachusetts 

 have led in the framing of these laws 

 and other states are following the good 

 example set by these two older com- 

 monwealths, where the conditions seem 

 to have reached a maximum of harm- 

 fulness (see Ward, 1918, 1919). 



During recent years stream pollution 

 has enormously increased and the prob- 

 lems arising from this condition have 

 been investigated by many biologists 

 and sanitary engineers. The former 

 have studied the problem from the 

 viewpoint of its effect on the useful 

 animal life, especially fishes and river 

 mussels, and this phase probably bears 

 as close a relation to human welfare as 

 any other. Of course, from the stand- 

 point of health, the polution problem 

 is of paramount importance because of 

 its bearing on such diseases as typhoid 

 fever which may be caused by a pol- 

 luted water supply. 



Perhaps the worst effect of chemical 

 pollution is to be found in the streams 

 of western Pennsylvania, where mine 

 water heavily loaded with oil or acid 

 water from coal mines is permitted to 

 flow into the rivers and streams of this 

 part of the state. Studies by Ortmann 

 (1909) show that whole stretches of 

 the Allegheny, Ohio, and Monongahela 

 rivers have been made into deserts, 

 as far as the animal life is concerned, by 

 the large amount of poisonous sub- 

 stances discharged into these streams 

 by the mines, oil industries, and chemi- 

 cal and other factories that border 

 these rivers. In the Susquehanna 



