by George Wuerthner, Bend, OR
One of the justifications often given for thinning the forest through various legislative efforts, such as the Fix Our Forest Act or the repeal of the Roadless Rule, as well as others, is the assumption that logging the forest will reduce the overall mortality of trees resulting from wildfires.
A new study, Cumulative Severity of Thinned and Unthinned Forests in a Large California Wildfire, published in the journal Land questions that assumption. The main problem with the idea that logging in the forest saves trees is that it overlooks the mortality from chainsaws.
As the abstract notes: “Thinning is widely conducted on public and private forestlands as a fire management approach designed to reduce fire severity and associated tree mortality. However, tree mortality from thinning itself, before the occurrence of the wildfire, is generally not taken into account, which leaves a potentially important source of tree loss, with its associated forest carbon loss and carbon emissions, unreported.”
In the above study, a comparison of 314 plot locations of tree loss was conducted between thinned forest stands and untouched stands before a wildfire. Following the 2021 Antelope Fire in Northern California, the researcher found that commercial thinning was associated with significantly higher overall tree mortality levels (cumulative severity).
The removal of trees prior to the fire has ecological impacts after the fire. Thinned stands had fewer snags, a crucial physical component for many wildlife species, such as cavity-nesting birds. Thinned stands also had less carbon stored on site. Even burnt trees store carbon for decades if not longer.
A further problem with thinning is that wildfire seldom encounters the majority of treated forest stands; thus, the forest ecosystem suffers the loss of trees, and the associated harmful collateral damage associated with logging, such as spread of weeds, sedimentation from logging roads into waterways, disturbance to wildlife, and other well-documented impacts related to logging.
This study is yet another reason to question the assertion that logging will increase “forest health” and reduce tree mortality.