(The following information was written and provided to me by George Wuerthner, author of Wildfire: A Century of Failed Forest Policy. – mk)
This study, Wildfire and Fuel Treatment Effects on Forest Carbon Dynamics in the Western United States, while focused on carbon losses and storage in forests, makes the point about probability – i.e. what is the likelihood of any fire actually interacting with fuel reductions? We can’t treat entire forests or even a significant portion of them due to cost and the undesirable impacts associated with logging, so it’s reasonable to ask the question as to whether there is a good chance as to whether a fire will actually burn through fuel reduction treated areas.
In other words since we can’t predict where a fire will occur, we can’t effectively treat forests with fuel reductions – even if they worked well – which they often don’t for a host of reasons including the fact that fuel reductions lose effectiveness over time.
We are spending a lot of federal dollars trying to treat forests to reduce fire spread and severity when the chances or probability that a high severity fire will actually interact with a treated forest is low. This, of course, again makes the case that treatments, if they are done at all, should be strategic and focused on lands near communities and other targeted areas of importance.
Sequestration of carbon (C) in forests has the potential to mitigate the effects of climate change by offsetting future emissions of greenhouse gases. However, in dry temperate forests, wildfire is a natural disturbance agent with the potential to release large fluxes of C into the atmosphere. Climate-driven increases in wildfire extent and severity are expected to increase the risks of reversal to C stores and affect the potential of dry forests to sequester C. In the western United States, fuel treatments that successfully reduce surface fuels in dry forests can mitigate the spread and severity of wildfire, while reducing both tree mortality and emissions from wildfire. However, heterogeneous burn environments, site-specific variability in post-fire ecosystem response, and uncertainty in future fire frequency and extent complicate assessments of long-term (decades to centuries) C dynamics across large landscapes. Results of studies on the effects of fuel treatments and wildfires on long-term C retention across large landscapes are limited and equivocal. Stand-scale studies, empirical and modeled, describe a wide range of total treatment costs (12–116 Mg C ha−1) and reductions in wildfire emissions between treated and untreated stands (1–40 Mg C ha−1). Conclusions suggest the direction (source, sink) and magnitude of net C effects from fuel treatments are similarly variable (−33 Mg C ha−1 to +3 Mg C ha−1). Studies at large spatial and temporal scales suggest that there is a low likelihood of high-severity wildfire events interacting with treated forests, negating any expected C benefit from fuels reduction. The frequency, extent, and severity of wildfire are expected to increase as a result of changing climate, and additional information on C response to management and disturbance scenarios is needed improve the accuracy and usefulness of assessments of fuel treatment and wildfire effects on C dynamics.
Another long term study – this one in the Siskiyou Mountains of Oregon – demonstrates that fires are episodic and tightly bound with climate. It also points out that sediment loads increased dramatically after logging began–that has no previous analogue in history.
This paper documents how changing climatic conditions impact fire regimes and frequency. There were long periods without fires as reported in other recent studies and then periodic fire decades as well. In general this paper would support the notion that juniper and pinyon woodlands were not characterized by “frequent fire/low intensity” fire regimes.