338 Mans Work on the Farm 



have not only turned out their inhabitants, animal and 

 vegetable, but have made their influence felt over a 

 much wider space than that which they actually cover. 

 Even where wild plants have been turned out only to 

 make way for cultivated ones, the result has been 

 similar in some degree. The earth bears better crops, 

 no doubt, at least from man's point of view, but they 

 are less crowded, and the fields are bare for some part 

 of the year. 



But besides cutting down woods and forests and 

 clearing away bush, man has drained fields, as well as 

 marshes, he has cut canals, and he has taken plants 

 from one land to another and from one hemisphere to 

 another, in many cases intentionally, but in many 

 others quite unintentionally. 



Other changes, though man has been the cause of 

 them, have taken place altogether without design on 

 his part ; and even where he has intended to make 

 some change, he has not seldom found that he has 

 done a good deal more than he meant, and has in fact 

 started a whole series of changes. 



Trees, for instance, are cut down for the sake of the 

 timber they will furnish, and nothing else, perhaps. 

 But a great deal more is done than merely to take 

 away so many loads of wood. To begin with, the soil 

 is exposed and dried, and the plants which have 

 flourished in the shade and moisture will die off. The 

 insects which fed upon the plants will die off too, and 

 the birds which fed on the insects and found shelter in 

 the trees will be driven away. 



If the trees are simply cut down, and the ground is 

 left unoccupied, it will be gradually taken possession 

 of by other plants or trees. In Germany, where the 



