Friday, October 2, 2009
Seeing the Forests for the Trees
There’s an old cliché that one can’t see the forest for the trees. It is used to describe people who are so focused on some detail that they fail to see the big picture. Nowhere is this failure to see the forest for the trees more evident than the rush to utilize dead trees for biomass fuel s and/or the presumed need to “thin” forests to reduce so called “dangers” and/or “damage” from wildfire and beetle outbreaks.
Contrary to popular opinion, we probably do not have enough dead trees in our forest ecosystems. And this deficit is a serious problem since dead trees are critical to the long term productivity of forests, and perhaps more important to forest ecosystems than live trees. Dead trees are not a “wasted” resource. It is questionable whether we can we remove substantial quantities of live or dead wood from the forest without serious long term biological impoverishment to forest ecosystems.
An abundance of dead trees, rather than a sign of forest sickness as commonly portrayed, demonstrates that the forest ecosystem is functioning perfectly well. For far too long we have viewed the major agents responsible for creation of substantial qualities of dead trees--beetles and wildfire—as “enemies” of the forest, when in truth; they are the major processes that maintain healthy forest ecosystems.
Recent research points out the multiple ways that dead trees and down wood are critical to the forest. One estimates suggests that 2/3 of all species depend on dead trees/down wood at some point in their lives.
Dead trees are very important for functioning aquatic ecosystems as well. Trees create structure in streams that shapes stream channels, reduces water velocity and erosion, and provides both food and habitat for many aquatic invertebrates. In general the more wood you have in the stream, the more fish, insects, and other aquatic life. Aquatic ecologists generally believe that there is no upper limit for dead wood in streams.
Once a tree falls to the ground and gradually molders back into the soil, it provides home to many small insects and invertebrates that are the lifeblood of the forest, that help recycle and produce nutrients important for present and future forest growth. For instance, there are hundreds of species of ground nesting bees that utilize down trees for their home. These bees are major pollinators of flowers and flowering shrubs in the forest.
Ants are among the most abundant invertebrates in the forest and many live in down trees and snags. Ants play a critical role in the forest, helping to break down wood, aeration of soil with their burrows, and protection of trees against the onslaught of other insects. One study found that ants killed 85% of the tussock moths that attacked Douglas fir and there are many other examples of how ants protect trees from tree predators.
And it’s not just wildlife that depends on dead trees. A recent review of 1200 lichen species found that 10% were only found on dead trees, and many others prefer dead trees as their prime habitat. Lichens, among other things, are important convertors of atmospheric nitrogen into fixed nitrogen important for plant growth.
Even the charcoal that results from wildfires burning up trees is important for soil productivity, helping to increase soil nutrients, water-holding capacity, and as a long-term storage mechanism for carbon.
Most beetle and wildlife events do not kill all the trees. Instead, they create a mosaic of age classes that actually increases biodiversity. Contrary to the popular opinion that beetles “destroy the forest” and fires “sterilize” the soils or create biological deserts, several recent studies have concluded that both beetle killed forests and the burned forests that result remain after stand replacement wildfires have among the highest biodiversity of any habitat type.
Notwithstanding, the fact that much new research suggest that both thinning or biomass removal are often ineffective at slowing or stopping large fires or insect outbreaks because these events are primarily driven by climatic/weather factors rather than fuels, there is the issue of whether the cure is worse than the so-called disease.
Logging, thinning, biomass removal and other forest management introduce all kinds of negative impacts to the forest ecosystem from the spread of weeds to soil compaction to alteration of water flow, disturbance to wildlife, creation of new ORV trails, increases in sedimentation, that all lead to the degradation of the forest ecosystem itself. Most of these negative impacts are ignored or glossed over by proponents of thinning and biomass removal.
In short, current efforts to thwart, and stop beetle outbreaks and wildfires create “unhealthy forests”. In fact, nearly everything that foresters do from thinning forests to suppressing fires degrades and impoverishes the forest ecosystem. Forest “management” is so focused on trees and wood products, that it represents a critical failure to see the forest through the trees.