By Jennifer Luetkehans, Crag Intern

Since we were young, watching Smokey the Bear and Bambi on TV, we have been taught to fear fire. Driving along the highway or hiking through the woods, we come upon blackened skeletons of trees, turning the landscape into an archetypal wasteland. On our nightly news we see firefighters battling huge flames, lighting up the crowns of once majestic trees. The media portrays fire as harmful and dangerous, but fails to tell us the full story. The Forest Service has taken a similar tack to the issue even though they know the issue is far more complex.

To help prevent fire, the public is told that we must “thin” the forest. Thinning implies the removal of smaller, more fire-susceptible trees and brush from our forests. Younger, smaller trees have thinner bark and are, therefore, more likely to burn. Large trees, on the other hand, have thicker bark and are more likely to survive a fire. Forest Service officials claim that humans can thin forests to recreate historic forest dynamics. Removing excess trees, they say, will reduce the amount of flammable fuels and stimulate the growth of the remaining trees by removing competition.

Is thinning the forest a good idea? The term “thinning” suggests a more-benign approach to forest management. Rather than clearcutting, the term suggests a more selective and careful approach. Thinning can be accomplished in a variety of way – either naturally through fires or insects or through human intervention. For example, we can allow controlled fires to burn selected forested stands. Thinning may involve the removal by hand of smaller trees below a certain diameter. Thinning can also involve logging, including the removal of smaller and larger trees using mechanical equipment. These “thinning” operations can amount to virtual clear-cutting.

The idea of thinning forests may sound like good old common sense, but accomplishing our forest restoration goals through human intervention has other consequences. To thin the forests through mechanical means building roads and disturbing soils, and doing so repeatedly over time to maintain the desired conditions. Forests are complicated communities, not just collections of trees. Thinning removes hiding cover for wildlife, and disrupts natural processes.

Under the Bush Administration, the Forest Service promoted thinning as a way to restore healthy forests and limit both the number and extent of fires in forests. The theory is that if smaller trees are removed, less fuel means that the fires may be cooler and less likely to damage the larger trees. Yet, the answer is not that simple. Forest fires are primarily driven by climate conditions-the best weather for fire is a combination of sustained drought and heavy winds. In these conditions, even thinned forests will burn up and no amount of fire fighting will stop the blaze. On windy days, flames and sparks can be carried long distances, even over treeless areas. For thinning to be effective, trees would have to be a great distance apart with large spaces between tree crowns and all ground cover would need to be removed. This is not most people’s idea of a healthy forest.

Thinning can also remove the canopy and the cool and damp micro climates that these canopies provide on the forest floor. Without sufficient canopy, these forests will become drier from sun exposure and wind speeds will increase. In this way thinning may actually increase both the risk and size of future fires.

Generally speaking, thinning activities seek to space out trees and create a more park-like environment in forests. Although lower-elevation ponderosa groves may fit this fold, many other forests do not. Higher-elevation mixed conifer forests may be quite dense and contain a diversity of tree species that have evolved with fire. To thin these forests is to try to change them into something they are not.

Forest stands are diverse and a one-size-fits-all approach to reducing fire risk through thinning will have negative consequences for biodiversity. In naturally dense forests, wildlife require cover to avoid being seen by either predator or prey. By removing cover, humans are removing habitat for wolves, foxes, fishers, raptors, and other animals. The loss of anchoring tree roots also causes erosion of soil and transportation into nearby rivers and streams, suffocating fish and choking their spawning grounds.

Different types of forests also have different fire cycles. For many forests fire is a natural part of the ecosystem and provides many beneficial functions. Fire creates standing and downed snags for animal habitat, provides ash that replenishes nutrients in the soil, and smoke that kills plant pathogens in trees. Some tree seeds cannot germinate without intense heat (lodgepole pine) and fire is needed for reproduction. A large wildfire may be catastrophic in human terms because it destroys a person’s home, but these fires are not catastrophic in nature’s eyes. More often, fires burn in a mosaic pattern leaving patches of green and growing trees and providing a flush of nutrients.

Fire restores the system, thins out the forest and stimulates tree growth by removing competing trees. Logging involves the use of heavy equipment to remove the commercially valuable tree and the building of roads to get the equipment in and haul the trees out. Fire involves neither. These logging roads cause erosion, habitat fragmentation, soil compaction and the introduction of invasive species. Fire restores healthy forests, while commercially-driven thinning requires the removal of the very thing sought to be protected – larger trees.

Like any project, thinning costs money. While smaller diameter trees may have some value, the costs of thinning projects must be borne by the forest through the harvest of large trees. The removal of large, fire-resistant trees makes the forest more susceptible to fire while losing a vital part of ecosystem necessary for habitat, shade, and vegetation.

Today, thinning is being used as a blanket policy over many different types of public forest lands. Rather than calling the project a logging project, the agency calls it a vegetation management project designed to restore forest health. In some cases, this may well be the result, in others the project is the same old thing dressed up in a positive spin.

Forests have evolved with fires and insects for millennia, and we have only begun to comprehend the complex relationship between natural disturbance and healthy forests. While we must find more sustainable ways to provide for our needs, we must also heed the cautions of the scientific community. We must seek out and rigorously test our assumptions with courage and honesty, and find the practices that work for this and future generations.

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