WORK OF THE UNITED STATES FOREST SERVICE 19 
During the period 1935-37, an annual average of more than 
173,000 acres in the national forests were reforested. In terms of 
trees, this represents a total planting over the 3-year period of more 
than 500 million trees. 
PROTECTION OF NATIONAL FORESTS 
Fire is an ever-present danger on the national forests. The great 
size of the forests compared with the size of the patrolling force, 
difficulty of reaching remote areas across miles of wilderness, dry 
air, and light rainfall in parts of the West, prevalence of lightning 
in the mountains, and constant use of fire in the daily lives of 
F- 281525 
FIGURE 14.—Crew constructing buttress for bridge across Elder Creek in the Fremont 
National Forest, Oreg. 
people and in industries all combine to make the fire hazard great. 
Visitors also contribute to the danger. Sometimes the Forest Service 
has to fight 10,000 or more fires within national-forest boundaries in 
a single year. 
Among the chief causes of fire on national forests are hghtning, 
smokers, Incendiarism, campers, debris burning, lumbering opera- 
tions, and railroads. More than half of the forest fires within the 
national forests are man-caused, 
Even a small fire may spread into a conflagration. Care with fire, 
matches, and burning tobacco is the first rule observed by every 
good woodsman. Fires may start in a remote locality and reach 
vast proportions before a party of fire fighters can get to the scene, 
no matter how promptly the start is made. Under particularly dry 
weather conditions, the forests may be said to be almost explosively 
inflammable. Because of this, the Forest Service lays tremendous 
stress upon forest-fire prevention. It is much cheaper to prevent 
fires than to fight them once they start. 
