Why Does the American West Have So Many Wildfires?
This practice has resulted in increasingly dense forests and ample thickets on the forest floor. As a result, forests eventually become “tinderboxes” for more explosive fires, said Jennifer Marlon, a research scientist at the Yale School of the Environment and creator of the Global Paleofire database, a collection of fire history records.
“If you have fuels that are more densely packed, they will burn hotter and faster and more intensely,” said Dr. Marlon.
Experts say firefighting has also altered the forest floor, making fires more severe. There are now more fire intolerant shrubs and tree species, such as white spruce, at lower elevations. White spruces have needles running down their trunks that serve as ladders to the canopy, creating crown fires that are the most difficult to control and the most deadly to trees.
In recent years, firefighting has changed to using “prescribed” or controlled burns to treat fire-prone land by thinning the brush. Last year, the Forest Service used prescribed fires on a record 1.8 million acres of federal land. The agency hopes to ramp up operations across the country in the coming years, but public reaction to the practice has increased. Opponents point to prescription fires that sometimes spiral out of control, such as in New Mexico earlier this year.
As the western population grows, so does the risk of a wildfire.
Half of all forest fires are ignited by lightning strikes. The other half is ignited by people, either indirectly – cut power lines, or sparks from a train as the wheels press against the rails – or directly, by discarded cigarettes, cars going backwards or campfires.
Wildfires ignited by human activity spread more than twice as fast and killed more trees than those ignited by lightning. research presented at a 2020 meeting of the American Geophysical Union. “Where people live, we provide opportunities for fires to start,” said Dr. tingley.