PrepTest 72, Section 4, Question 1

In the last half-century, firefighters in North America have developed a powerful system for fighting wildfires using modern technology. But at the same time, foresters and ecologists are increasingly aware that too much firefighting can be worse than none at all. Over the millennia, many forest ecosystems have evolved in such a way that they are dependent on periodic fires for renewal and for limiting damage when fires do occur. Ancient ponderosa forests, for example, were stable in part because low-intensity fires maintained open forests with low levels of fuel for future fires. These fires burned lightly around the bases of mature trees, leaving these trees alive and clearing the understory of brush and young trees. Scientists can easily count the regular recurrence of fires in these forests over the centuries by examining the scars left on trunks; the typical interval between fires could be as short as 5 years and rarely extended beyond 25 years.

If fires are kept out of forests, however, deadwood and other fuels build up; then, when fire is sparked by lightning or some other cause, what results is a fire so large that it leaves total devastation. Such fires often kill off wildlife that might escape low-intensity fires, and they also reach the crowns of centuries-old trees, destroying them and ultimately enabling rains to erode the unprotected topsoil. Because of the relative success of fire-suppression efforts, many forests, including ponderosa forests, have now been free of fire for 50 years or longer, leaving them vulnerable to these devastating crown fires. It is therefore increasingly necessary for land managers in North America to strive to manage rather than eliminate fires; land management policies should recognize the essential role that fire plays in many ecosystems.

Fire behavior depends on the complex interaction of three factors�topography, weather, and fuel�and since topography is fixed and weather is unpredictable, fuel is the only element that land managers can control. Land managers should therefore focus their efforts on fuel. A new kind of wildfire management that is designed to simulate the natural role of fire through a combination of selective harvesting and prescribed fires is the most promising method for controlling fuel. Selective timber harvesting focuses on smaller trees�markets for this smaller material do exist�leaving the larger, fire-tolerant trees on the land and thinning the forest, thereby re-creating the conditions that allow for low-intensity burns. Prescribed fire management includes both the intentional lighting of controlled burns and the policy of allowing fires set by lightning to burn when the weather is damp enough to reduce the risk of extensive damage. Once fuels are reduced by these fires, maintenance burns at 15- to 20-year intervals will be needed. When wildfires inevitably occur, they will be more easily controlled and do much less damage.

In the last half-century, firefighters in North America have developed a powerful system for fighting wildfires using modern technology. But at the same time, foresters and ecologists are increasingly aware that too much firefighting can be worse than none at all. Over the millennia, many forest ecosystems have evolved in such a way that they are dependent on periodic fires for renewal and for limiting damage when fires do occur. Ancient ponderosa forests, for example, were stable in part because low-intensity fires maintained open forests with low levels of fuel for future fires. These fires burned lightly around the bases of mature trees, leaving these trees alive and clearing the understory of brush and young trees. Scientists can easily count the regular recurrence of fires in these forests over the centuries by examining the scars left on trunks; the typical interval between fires could be as short as 5 years and rarely extended beyond 25 years.

If fires are kept out of forests, however, deadwood and other fuels build up; then, when fire is sparked by lightning or some other cause, what results is a fire so large that it leaves total devastation. Such fires often kill off wildlife that might escape low-intensity fires, and they also reach the crowns of centuries-old trees, destroying them and ultimately enabling rains to erode the unprotected topsoil. Because of the relative success of fire-suppression efforts, many forests, including ponderosa forests, have now been free of fire for 50 years or longer, leaving them vulnerable to these devastating crown fires. It is therefore increasingly necessary for land managers in North America to strive to manage rather than eliminate fires; land management policies should recognize the essential role that fire plays in many ecosystems.

Fire behavior depends on the complex interaction of three factors�topography, weather, and fuel�and since topography is fixed and weather is unpredictable, fuel is the only element that land managers can control. Land managers should therefore focus their efforts on fuel. A new kind of wildfire management that is designed to simulate the natural role of fire through a combination of selective harvesting and prescribed fires is the most promising method for controlling fuel. Selective timber harvesting focuses on smaller trees�markets for this smaller material do exist�leaving the larger, fire-tolerant trees on the land and thinning the forest, thereby re-creating the conditions that allow for low-intensity burns. Prescribed fire management includes both the intentional lighting of controlled burns and the policy of allowing fires set by lightning to burn when the weather is damp enough to reduce the risk of extensive damage. Once fuels are reduced by these fires, maintenance burns at 15- to 20-year intervals will be needed. When wildfires inevitably occur, they will be more easily controlled and do much less damage.