Livestock Major Factor in Unhealthy Forests 1
|Livestock have actively participated in the destabilization of ponderosa pine and mixed coniferous forests. The hot fires that swept through central and eastern Washington and Oregon during the summer of 1994 may have, in fact, been partially a result of a century of livestock grazing.|
Dr. Joy Belsky and Dana Blumenthal 2
The classic "park-like" stands of ponderosa pine and mixed conifer forests that once blanketed the interior West from British Columbia to New Mexico have changed dramatically for the worse since Euro-American invasion.
What were once widely spaced, fire-tolerant forest stands with a dense grass sward underneath have been converted over the last century to thick stands which are more fire-sensitive and susceptible to disease. Scientists, government foresters, the timber industry and conservationists have identified two major factors causing this transition: (1) prevention of low-intensity fires that suppressed the number of fire-sensitive and shade-tolerant tree species such as Douglas, grand and white firs, and (2) logging the economically valuable and fire-resistant ponderosa pine and western larch.
Today, there is much talk, though little action, about the "forest health crisis." Of course, a healthy forest to an ecologist or conservationist is not the same as to a mill owner or government bureaucrat. They vehemently differ in the relative importance of logging, fire suppression, disease and roading to forest sustainability.
Only 2-8 percent of original old growth ponderosa pine forest still exists in Oregon. The numbers are similar throughout the West.
While these are very important factors, a third factor has been overlooked in the debate. A major force in changing the forests has been livestock grazing.
Livestock range over 284 million acres or 91percent of all federal land in the eleven western states. Though livestock do not wield chainsaws, they nonetheless have dramatic effects on forest composition and density.
Livestock grazing has modified forest dynamics by removing the understory grasses, which serve two critical roles in a natural forest.
First, healthy, thick grass out competes conifer seedlings and prevents the heavy densities of small trees.
The forest floor was once carpeted with Idaho fescue and bluebunch wheatgrass, pinegrass and elk sedge. These "old-growth" grasses with their extensive roots could out compete little tree seedlings for moisture and nutrients. Besides serving as a source of nutrients and organic matter, the litter is critical for slowing surface water flow, enhancing water infiltration, insulating the soil from freezing, and mitigating the erosive force of raindrops.
Second, the natural grass stands served as fine fuels to carry low-intensity fires through the forest, which also keep tree numbers down.
On the dry low-elevation south-facing slopes, the dominant tree was ponderosa pine. In wetter mid-level north-facing stands, the dominant trees were western larch, and Douglas, grand and white firs. Those that made it to maturity evolved with fire to have self-pruning and thick fire-resistant bark, so the frequent ground fires that came an average of every 5-12 years throughout the West were usually no problem to the big old trees.
Gone with the grass are these beneficial fires. Dense stands of sapling- and pole-sized fire-sensitive species are now all too common. These species are more susceptible to stress during drought, making them more vulnerable to diseases and insect infestations. Fuel loads have increased ten-fold in the last 25 years.
Dr. Joy Belsky and her associate, Dana Blumenthal, reviewed the scientific literature and found numerous examples comparing grazed and ungrazed (livestock was excluded, but not native wildlife), mostly unlogged forest stands. They found that the ungrazed stands retained their park-like character, in spite of active fire prevention and the absence of logging. 3
To restore the stability and sustainability of our interior forests, we must not only stop logging the big trees and carefully reintroduce fire into the ecosystem, but also end livestock grazing so the grass can return.
The solution is not salvage logging. The trees that need to be reduced in the forest are the small-diameter, less economically valuable species. The trees that need to be retained and enhanced are the large-diameter, more economically valuable species. Numerous government attempts to offer salvage sales that emphasize the former, without sweetening the pot with the latter, have conclusively shown that the market isn't interested, because there is no money in it.
This ecological debt must be paid off by investing in true forest restoration, not merely continuing to subsidize grazing and timber sales. The cow may be mightier than the chainsaw, not only in myth, but also in fact.
1. Adapted from Kerr, A. 1996. Livestock major factor in unhealthy forests. Wallowa County Chieftan (Sept. 12, 1996).
2. Belsky, A. J. and D. M. Blumenthal. 1997. Effects of livestock grazing on stand dynamics and soils in upland forests of the interior West. Cons. Biol. 11: 315-427