Our forests are exposed to destruction by many enemies, the worst of which is fire. From 8,000,000 to 12,000,000 acres of forest lands annually are burned over by destructive fires. These fires are started in many different ways. They may be caused by sparks or hot ashes from a locomotive. Lightning strikes in many forests every summer, particularly those of the Western States, and ignites many trees. In the South people sometimes set fires in order to improve the grazing. Settlers and farmers who are clearing land often start big brush fires that get out of their control. Campers, tourists, hunters, and fishermen are responsible for many forest fires by neglecting to extinguish their campfires. Sparks from logging engines also cause fires. Cigar and cigarette stubs and burning matches carelessly thrown aside start many forest fires. Occasionally fires are also maliciously set by evil-minded people.
The officers of the National Forests in the West have become very expert in running down the people who set incendiary fires. They collect evidence at the scene of the fire, such as pieces of letters and envelopes, matches, lost handkerchiefs and similar articles. They hunt for foot tracks and hoof marks. They study automobile tire tracks. They make plaster of Paris impressions of these tracks. They follow the tracks—sometimes Indian fashion. Often there are peculiarities about the tracks which lead to the detection and punishment of the culprits. A horse may be shod in an unusual manner; a man may have peculiar hob nails or rubber heels on his boots or else his footprints may show some deformity. The forest rangers play the parts of detectives very well. This novel police work has greatly reduced the number of incendiary fires.
FOREST FIRES DESTROY MILLIONS OF DOLLARS WORTH OF TIMBER EVERY YEAR
A forest fire may destroy in a few hours trees that required hundreds of years to grow. A heavy stand of timber may be reduced to a desolate waste because some one forgot to put out a campfire. Occasionally large forest fires burn farm buildings and homes and kill hundreds of people. During the dry summer season when a strong wind is blowing, the fire will run for many miles. It always leaves woe and desolation in its wake. A mammoth forest fire in Wisconsin many years ago burned over an area of two thousand square miles. It killed about fourteen hundred people and destroyed many millions of dollars worth of timber and other property. A big forest fire in Michigan laid waste a tract forty miles wide and one hundred and eighty miles long. More than four billion feet of lumber, worth $10,000,000, was destroyed and several hundred people lost their lives. In recent years, a destructive forest fire in Minnesota caused a loss of $25,000,000 worth of timber and property.
There are several different kinds of forest fires. Some burn unseen two to four feet beneath the surface of the ground. Where the soil contains much peat, these fires may persist for weeks or even months. Sometimes, they do not give off any noticeable smoke. Their fuel is the decaying wood, tree roots and similar material in the soil. These underground fires can be stopped only by flooding the area or by digging trenches down to the mineral soil. The most effectual way to fight light surface fires is to throw sand or earth on the flames. Where the fire has not made much headway, the flames can sometimes be beaten out with green branches, wet gunny sacks or blankets. The leaves and debris may be raked away in a path so as to impede their advance.
Usually in the hardwood forests, there is not much cover, such as dry leaves, on the ground. Fires in these forests destroy the seedlings and saplings, but do not usually kill the mature trees. However, they damage the base of the trees and make it easy for fungi and insects to enter. They also burn the top soil and reduce the water-absorbing powers of the forest floor. In thick, dense evergreen forests where the carpet is heavy, fires are much more serious. They frequently kill the standing trees, burning trunks and branches and even following the roots deep into the ground. Dead standing trees and logs aid fires of this kind. The wind sweeps pieces of burning bark or rotten wood great distances to kindle new fires. When they fall, dead trees scatter sparks and embers over a wide belt. Fires also run along the tops of the coniferous trees high above the ground. These are called "crown-fires" and are very difficult to control.
The wind plays a big part in the intensity of a forest fire. If the fire can be turned so that it will run into the wind, it can be put out more easily. Fires that have the wind back of them and plenty of dry fuel ahead, speed on their way of destruction at a velocity of 5 to 10 miles an hour, or more. They usually destroy everything in their course that will burn, and waste great amounts of valuable timber. Wild animals, in panic, run together before the flames. Settlers and farmers with their families flee. Many are overtaken in the mad flight and perish. The fierce fires of this type can be stopped only by heavy rain, a change of wind, or by barriers which provide no fuel and thus choke out the flames.
Large fires are sometimes controlled by back-firing. A back-fire is a second fire built and so directed as to run against the wind and toward the main fire. When the two fires meet, both will go out on account of lack of fuel. When properly used by experienced persons, back-fires are very effectual. In inexperienced hands they are dangerous, as the wind may change suddenly or they may be lighted too soon. In such cases they often become as great a menace as the main fire. Another practical system of fighting fires is to make fire lines around the burning area. These fire lines or lanes as they are sometimes called, are stretches of land from which all trees and shrubs have been removed. In the centre of the lines a narrow trench is dug to mineral soil or the lines are plowed or burned over so that they are bare of fuel. Such lines also are of value around woods and grain fields to keep the fire out. They are commonly used along railroad tracks where locomotive sparks are a constant source of fire dangers.