Spreading wildfires could bring 'an inferno on earth'

Fire patterns have changed over time as human populations have grown and altered landscapes by clearing forests, allowing pasture animals to overgraze grasslands, and importing new plant species. Across parts of the western United States, for example, cheatgrass, an invasive annual adapted to frequent burns, has supplanted native brush, desert shrub, and perennial grasses that typically experience longer intervals between fires. In other areas, mixed-age and mixed-species forests have been replaced by single-species plantations where flames can jump easily from tree to tree. The result, instead of a low-intensity restorative fire, is a fire so hot that it can cause lasting harm to soils. Humans have also altered fire patterns through deliberate suppression. After 1910, when a severe wildfire charred more than 3 million acres of western US forest in just two days, the strong desire to protect timber resources gave life to a policy of quickly extinguishing fires. For decades firefighters proved remarkably successful in this endeavor, but the upshot was that forests became so loaded with fuel that a blaze that evaded control could quickly grow into a dangerous megafire. Now policies are shifting in many places to let some fires proceed naturally or through preventative controlled burns; yet by warming the planet, we may be relinquishing even more control than we bargained for...read more