28 ANIMAL ECOLOGY 



lands, the draining and filling of depressions, the 

 flooding of the lands, the destruction (or succession) 

 of plant and animal associations (including crop rota- 

 tion), are processes brought about or practiced by 

 other organisms or animal agencies. An ecological 

 standpoint gives us a consistent, comprehensive 

 orientation of all these natural and " artificial " ac- 

 tivities and processes, and shows the unity in all 

 organic responses to the environment. Man's in- 

 fluence in the main consists of hastening or retarding 

 "natural processes." 



Naturalists have for a long time spoken of the 

 " balance of nature " and of the all-pervading in- 

 fluence of any serious disturbance of it. This 

 balance is, of course, only a relative condition, and 

 not absolutely fixed. It swings from one side, then 

 back, sometimes showing considerable amplitude 

 in its swing, then again its moves are very slight, 

 mere tremblings, as it were. But now and then 

 some local catastrophic event occurs which overturns 

 everything, as when a volcano becomes active, or 

 some dominant association takes possession of the field, 

 as in the case of man, and a new order is initiated 

 and a new balance is developed. The mongoose 

 in Jamaica, our English sparrow, and rabbits in 

 Australia are the classic examples of the overturning 

 of the local order of nature by the agency of other 

 organisms. Obviously this balance is not a con- 

 dition limited to any particular locality or group 

 of organisms. Balance is very generally conceded 

 to be of fundamental importance in the study of any 



