Is Wildfire Suppression in Giant Sequoia Groves a Problem, a Solution, or Neither?

ABSTRACT In 1910, the U.S. federal government began an official policy of suppressing wildfires. Decades later it became understood that the giant sequoia, the world's most massive tree, is serotinous and depends upon fire to effectively reproduce. For a century, fire was almost completely excluded from giant sequoia groves, until a series of lightning fires over the past decade. After these fires, U.S. land managers hypothesized that the blazes had caused unprecedented levels of high‐severity fire due to a century of fire suppression and fuel accumulation. Based on this assumption, U.S. legislation is now proposed to override environmental laws to allow logging in all giant sequoia groves on federal public lands, including in Wilderness Areas and national parks, in the name of wildfire prevention. In addition, lower‐severity prescribed fires are now being implemented as a means to prevent and suppress mixed‐severity wildfires, based on the assumption that high initial post‐burn sequoia seedling densities after prescribed fire will translate to relatively high densities in later years. I investigated the effects of wildfire suppression in giant sequoia groves using GIS data of wildfire perimeters dating back to 1910, fire severity data from 2012 to present, and a government prescribed fire and sequoia regeneration dataset. I found fire of all severities since 1910 is below frequencies that occurred before fire suppression. I found no correlation between time‐since‐fire and the percentage of area burned comprised by high‐severity fire in giant sequoia groves. Further, I found no correlation between initial (1 year post‐burn) sequoia seedling densities and densities at 10 years following prescribed fire. The percentage of all plots lacking any sequoia regeneration after prescribed fire increased significantly over time. Only 23% of prescribed fire plots lacked sequoia regeneration at 1 year post‐burn, while 82% of prescribed fire plots lacked sequoia regeneration at 20 years post‐burn.