A new tree-ring and fire scar study from SMU and the University of Arizona finds that today’s mega-wild fires in the Southwest are unusual.
The 1,400-year record encompassed the Little Ice Age (1600 to mid 1800s A.D.) and the Medieval Warm Period (800-1300 A.D.) and found that fire incidence was nearly the same under both cool and warm, wet and dry conditions.
Forest policy of fire suppression prevented forests being naturally thinned by relatively small ground fires. The result was a build up of brush which exacerbated fires to produce even larger, more destructive wild fires. The researchers say, “The U.S. would not be experiencing massive large-canopy-killing crown fires today if human activities had not begun to suppress the low-severity surface fires that were so common more than a century ago.”
“This new study is based on a first-of-its-kind analysis that combined fire-scar records and tree-ring data for Ponderosa Pine forests in the southwest United States.”
“Fire scientists know that in ancient forests, frequent fires swept the forest floor, often sparked by lightning. Many of the fires were small, less than a few dozen acres. Other fires may have been quite large, covering tens of thousands of acres before being extinguished naturally. Fuel for the fires included grass, small trees, brush, bark, pine needles and fallen limbs on the ground.”
“The fires cleaned up the understory, kept it very open, and made it resilient to climate changes because even if there was a really severe drought, there weren’t the big explosive fires that burn through the canopy because there were no fuels to take it up there.” “The trees had adapted to frequent surface fires, and adult trees didn’t die from massive fire events because the fires burned on the surface and not in the canopy.”
Read the entire press release from SMU here.
This study implies that attempts at “sustainable” forest management and endangered species issues have in fact made our forests more unsustainable.