To Prevent Forest Fires, Thinning is Not Always the Answer
By Catriona MacGregor Glazebrook and Walker Laughlin
Source: The TreeSpirit Project
Today’s fires are hotter, faster, and more destructive than ever. In fact, some recent fires in California have even earned a new name: ‘firenados.’ These tall, pyro-cumulus clouds ravage landscapes and communities with their lightning, thunder, and high winds. ‘Firenados’ are a powerful marker of the unprecedented speed and severity of fires today. In 2020 alone, California’s wildfires burned 4.2 million acres, damaged or destroyed 10,500 structures, and killed 31 people (Insurance Information Institute, 2020).
How do we protect our forests and communities from these threats? According to traditional thinking, the answer is forest thinning—cutting down trees to reduce the fuel for fires. Government agencies and most certified foresters follow this view. From 2014 to 2018, federal agencies harvested between 401 to 500 million board feet of wood each year in California (Congressional Research Service, 2019). California forestry agencies and the U.S. Forestry Service pledged in 2020 to thin out 1 million acres of forest each year by 2025 (State of California and U.S. Forest Service, 2020).
Yet, thinning is largely ineffective at preventing fires. It can even make them more harmful.
One reason is that fires need oxygen as much as they need wood to burn. Thinned and even heavily managed forests decrease forest density, allowing winds to travel uninterrupted (Aldous, 2018). Free winds provide fires with more oxygen, so fires move more rapidly and burn more ferociously. And in fact, high winds are a major factor in the massive fires we see today. Wildfires normally reach top speeds of six miles per hour in forests and 14 miles per hour in grasslands (Sweeney, 2020). Northern California’s Glass Fire traveled at an outstanding 40 mph, burning about 67,500 acres and destroying 1,555 structures. Its speed was largely due to severe wind conditions (Insurance Information Institute, 2020).
Another of thinning’s shortcomings is that it focuses on removing the largest trees. The timber industry often will try to cover their costs by taking out these more profitable trees, even though they make up only a small portion of fire fuels. The dry underbrush and leaves in forests are more responsible for fires (Calkin et al., 2014). Natural, unmanaged forests tend to have a denser population of trees, and dense plant life provides less readily available oxygen to fires. In addition, forests with high populations of plants tend to have more moisture in the soil and surrounding air. This is because of evapotranspiration—the process where plants and trees produce water vapor. Moist forests impede the spread of fires.
Recent research has shown that overall, thinning tends to do more harm than good. One of the most well documented studies surveyed 1,500 fires between 1984 and 2014 in pine and mixed-conifer forests of the western United States. It found that fires burned less severely in unthinned forests, despite having more biomass for fuel (Bradley, Hanson, and DellaSalla, 2016). Another study found that even under “best case” scenarios, thinning reduced 3.4 to 6.0 times more forest than it protected from burning (Odion et al., 2014).
Private landowners must understand that thinning will not stop a fire from reaching their property. Too often they are persuaded to thin trees around their homes and businesses. While this may make sense for trees that are close to built structures, many landowners waste precious time and resources cutting and removing trees on their acreage. They then neglect to directly fire-proof their buildings. Landowners should realign their priorities towards installing fire-retardant siding material, removing any fallen dry leaves or sticks near their buildings, and working with neighbors to develop a well-organized evacuation plan.
This last step is especially needed. During the Camp Fire, a blaze that killed 86 people, more than a third of the minority of Butte County residents who subscribed to fire emergency updates did not receive alerts (St. John and Serna, 2018). On the morning of the fire, three of Paradise’s 14 districts received warnings to leave instead of mandatory orders to leave (St. John and Lin, 2018). Three others did not even receive warnings. Because Paradise had no formal plan for a full evacuation and the town had narrowed the road that served as the primary escape path, escape routes gridlocked within an hour of the first evacuation order.
It is critical that we refocus our efforts from thinning forests to preparing communities for fire events and supporting the long-term health of forest ecosystems. As one major study puts it, we need to “accep[t]” wildfire as an inevitable catalyst of change and . . . promot[e] adaptive responses by ecosystems and residential communities to more warming and wildfire” (Schoennagel et al., 2017). Wellkind Forestry’s approach to dealing with climate change and fires is to promote greater forest health, resilience, and biodiversity.
By caring for our forests, we support critical ecosystems while protecting our communities. Forests that are full of trees provide enough water and atmospheric moisture to prevent the dry soils that fuel large fires. When we protect wildlife populations from threats like excessive thinning, they are free to moisturize and fertilize the soil with their droppings. Moist soil supports the health of trees in turn.
Moreover, preserving our local forests supports ecosystems on an international scale. Trees are a critical ally in the fight against climate change. Researchers from America’s National Academy of Sciences stress the importance of natural climate solutions (NCS), which include conservation, restoration, and/or improved land management practices on forests, wetlands, grasslands, and agricultural lands. The Academy’s 2017 study concludes that NCS can offer over one third of the climate mitigation the world needs to keep global warming below two degrees Celsius (Griscom et al., 2017).
Shedding outdated fire prevention methods frees us to use more innovative strategies to improve the health of forest ecosystems and keep our communities safe. There is an urgent need to improve soil quality, restore biodiversity, and harden forest ecosystems against drought and other threats. Likewise, our cities and towns must develop reliable communication channels and evacuation routes and harden their homes for fires. For both of these challenges, thinning is not the answer. We must re-focus our efforts towards strengthening the resilience of our communities and forest ecosystems.