Forest fuel treatments and wildfire risk

It is also important that the area adjacent to egresses from forest communities be kept reasonably clear, so residents can escape if a fire occurs.

So what about fuel treatments in the forest away from structures and infrastructure? Do such treatments keep anyone safer from fire, or does it keep the forest itself safer from fire? That is where the serious cost/benefit analysis is needed. Forest and fire ecology science indicates that in some situations, especially when fire is of low or medium intensity, there is a window of around a decade in which fuel treatments out in the forest can slow the spread of fire.

However, research also shows that the probability that any particular fuel treatment will actually moderate a fire before vegetation starts to substantially return is extremely low, typically about 1% per year.

Fuel treatments have been shown to do little good during the very high intensity fires that occur during hot, dry and windy weather. Embers can fly for miles and spread fires during “fire weather.” Also, in some cases the openness resulting from removing the majority of trees from large areas of forest can allow the wind to blow more freely and actually cause a fire to burn hotter. Additionally, thinned and open forests tend to be drier and possibly more flammable.

In 2016, three forest and fire ecology researchers, Bradley, Hanson and DellaSala, did a large scale study of forests across the West, including our dry southwestern forests. They found that forests that were not logged and did not receive fuel treatments burned less often and less severely than forests that were were logged and/or did receive fuel treatments. This study indicates that overall fuel treatments were not beneficial for reducing the amount and intensity of fire out in forests.

Forest fuel treatments cause much ecological damage such as disruption of wildlife habitat, erosion, soil compaction, and damage to the trees that are left standing, including risk of bark beetle attack. Because thinned areas are subsequently treated with prescribed fire at regular intervals, the understory is not allowed to substantially return. This leaves forest that is barren, dried out and ecologically dysfunctional. This has to be a part of the cost/benefit analysis, along with the health effects of frequent prescribed burn smoke on the public.

Our forests have evolved through fire, and fire of all intensities are a natural part of forest ecology. Fire promotes ecological diversity and helps forests to renew themselves. This includes even high intensity fire, although clearly no one wants high intensity fire to occur anywhere near communities, or to be very widespread.