PROTECTION 169 
they are in greatest abundance the tree is cut and 
consumed by fire. 
Logs cut in the summer must be barked in order 
to prevent the ravages of bark beetles. This is often 
necessary in the case of timber felled by the wind. 
4. Protection against Grazing and Browsing 
Animals.—An excess of grazing is, of course, in- 
jurious to forests; but, as I have already said in 
another chapter, the damage is more the effects of 
abusive overgrazing. Animals such as sheep and cat- 
tle, if hungry, will prevent the growth of trees, and 
injure the soil on hillsides by wearing paths which 
in time induce erosion and landslides. Pastures in 
which there is an abundance of grass are often in- 
vaded by trees of various kinds to such extent that 
their presence 1s objectionable. 
In many regions there is a constant struggle be- 
tween the prairie and forest. Wherever the forest 
must fight fire, browsing animals, and dry winds, the 
prairie is in time victorious. The damage caused 
by deer and other browsing animals, and by gnawing 
animals such as rabbits and squirrels, is insignificant 
in comparison with the injuries due to fire and in- 
sects. Often in nurseries small animals do a great 
deal of mischief in eating seeds and seedlings. The 
English sparrow is fond of the terminal bud of young 
conifers; in fact, almost all injurious animals prefer 
