Controversy exists over an alleged need to intensively thin forest vegetation for the purpose of reducing severe wildland fires. The “Healthy Forest Initiative” (HFI) stakes its foundation on the view that wildfires now burn larger areas more severely than ever before due to decades of fire exclusion and resultant fuel accumulation. The HFI would streamline federal environmental laws to expedite hazardous fuel reduction on public lands.

In the Klamath-Siskiyou region of northwest California and southwest Oregon, mixed conifer forests dominated by Douglas fir are likely to experience accelerated fuel treatments should the HFI become law because (1) it is the most widespread forest type in the region, (2) fire is a key natural disturbance in this forest type, and (3) dozens of federal projects with a stated purpose of reducing hazardous fuels are proposed in this forest type. This poses a conservation issue because Klamath-Siskiyou forests support globally outstanding temperate biodiversity. Incremental degradations of forests in this region may have disproportionately negative effects on biodiversity at continental and global scales.

Although changes in fire behavior and effects resulting from historic fire exclusion and logging practices in forests dominated by ponderosa pine are widely reported as fact, there is less certainty about such changes in Douglas fir forests, particularly in the Klamath-Siskiyou, where climate, topography, and soils exert widely variable influences on vegetation and disturbance regimes. Despite uncertainty, federal land managers in the region commonly assert that local forests are severely disrupted by fire exclusion, and propose intensive thinning across the landscape to restore conditions that resemble an historic range of variability.

This analysis gauges disruptions of fire ecology processes that have resulted from human activities based on regional studies of fire history, documentary records, and interpretations of fire events in the past two decades. It calls specific attention to gaps in scientific knowledge, and compares what is known about Klamath-Siskiyou forests with information cited by land managers in support of landscape fuel treatments. I argue that conclusions drawn from research conducted in other regions are not appropriately applied to Klamath-Siskiyou forests due to wide geophysical variations along the Pacific slope of North America.