Lodgepole pine forest in Yellowstone National Park - naturally dense with a large, high-intensity fires representing the natural fire regime.
Every Forest is Different
Here are some points to consider when thinking about forest fires:
1. Depending on the location, the following three abuses have damaged many of our forests:
- Over-grazing by sheep and/or cattle Removed grasses that would have carried low-intensity surface fires.
- Logging Destroyed and opened up old-growth forests, causing dense forest growth.
- Fire suppression, but only after many forests had been severely damaged by private interests This is a point many critical of government agencies have failed to recognize. Extinguishing fires shortly after they have started has allowed unnatural amounts of vegetation to build up in low to mid-elevation (below 7,000 feet) mixed-conifer and dry ponderosa pine forests.
2. Large, high-severity fires driven by logging/over-grazing damage and climate change may be causing ecological damage to some dry ponderosa forests in Arizona and New Mexico by eliminating potential conifer seed sources, thus lengthening the time it takes for conifers to re-colonize an area.
3. Global climate change is raising temperatures in many forested areas in North America. Higher temperatures contributes to increased tree mortality, lengthening of fire seasons, and increasing the number of large, high-intensity fires.
4. Forests that naturally have large, high-intensity crown fires like the lodgepole pine forest shown in the photo above, have generally not suffered the same kind of damage that we have caused in dry ponderosa and mixed-conifer forests by over-grazing and logging.
Dead Trees and Bark Beetles
Despite all the hand waving and panic-filled pronouncements by some, tree mortality in many of our Western forests is not an ecological disaster nor does it automatically cause increased fire risk.
Scientific studies have consistently found that trees killed by drought and or beetles (drought is what weakens the trees to allow for beetle attack) do NOT increase risk or severity of wildfire. The most comprehensive study published in the Proceedings of the National Academy of Sciences concluded, "the annual area burned in the western United States has not increased in direct response to bark beetle activity" (Hart et al. 2015). A study from the University of Montana stated "weakening or eliminating environmental laws to allow more beetle timber harvest treatments is the wrong choice for advancing forest health in the United States" (Six et al. 2014).
Other papers concerning tree mortality in our forests: