SOME INDIRECT RESULTS 499 



THE COMPLEX OF LIFE 



I have already traced in the foregoing pages some ex- 

 amples of the secondary results of man's influence in Scotland : 

 the slaughter of birds of prey and increase of vermin, the 

 increase of cultivated crops which has multiplied gramini- 

 vorous beasts and birds, which again have benefited their 

 enemies, the beasts and birds of prey, and so on. Here I 

 would add a few more illustrations to emphasize how all- 

 pervading is the complex of life. 



It would be easy to invent a series of likely chains of 

 circumstance which ought to happen. It would be easy to 

 argue that the less wild ground there was for the rearing of 

 game the more gamekeepers would be necessary: for culti- 

 vation curtails wild ground, but cultivation increases the 

 numbers of insect pests, and this the number of insectivorous 

 birds ; these again increase the numbers of hawks and other 

 birds of prey, and so in the long run gamekeepers would 

 have to be multiplied. We are familiar too with Darwin's 

 famous chain of the cats, which, by eating field-mice, and 

 these by eating humble bees, diminish the clover crop, which 

 cannot form ripe seeds in the absence of the humble bee. 



But such sequences are frequently little more than purely 

 imaginary, since Nature is not restrained by the limitations 

 of human logic. Yet the succession of events in Nature is 

 no less striking. 



RABBITS AND VEGETATION 



Man introduced the wild Rabbit to Britain at a not very 

 distant date. It has spread from cultivated field to wild 

 glen and rocky hillside until it has possessed the land, And 

 everywhere it is affecting the vegetation. Mr E. P. Farrow 

 has shown that on moorland a favourite food is the tender 

 stems and shoots of heather (Calluna vulgaris], and as a 

 result, heather is eaten bare to the root. Under such con- 

 ditions, the heather moor rapidly degenerates, and benefiting 

 by the discomfiture of its rival, the sand sedge (Carex 

 arenarid] association of plants makes fresh growth and 

 captures the places formerly occupied by heather. This in 

 turn the Rabbits attack, making way for the advance of a 

 "grass-heath" association. So that a simple consequence 



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