ERI FAQ
Restoring the Southwestern Ponderosa Pine Forest
During the last 120 years southwestern ponderosa pine forests have radically changed. These ecosystem changes are a result of livestock grazing, high-grade logging, fire suppression, and some forms of recreation. Specific ecosystem changes include:
- Decreased cover of grasses and wildflowers
- Decreased wildlife diversity
- Increased densities of small, stunted trees
- Decreased numbers of large old-growth trees
- Increased old-growth mortality rates due to competition with thickets of small trees
- Increased threats of large-scale insect infestation of trees
- Change from frequent (every 2-8 years), low-intensity ground/grass fires (which serve to cycle nutrients and promote ecosystem health), to increasingly large catastrophic "crown" fires
- Large scars that fragment the landscape and threaten landscape-scale diversity
- Increasing threats to property and human lives
Scientists, environmentalists, public land-management agencies, and decision-makers agree that restoration of southwestern ponderosa pine forests is critical.
- "The way in which we have, through all the practices of grazing, logging, and fire suppression, put these forests at risk and changed them poses an extraordinarily urgent issue for restoration," Former Interior Secretary Bruce Babbitt, remarks before the "Steps Toward Stewardship" Conference, Flagstaff, Arizona. April 25, 2000.
- Stated goal of the Southwest Forest Alliance, in Forests Forever! : "Restore southwest forests to fully functioning ecosystems."
- "Time has run out. Knowing what we know now [about restoration], we must act, and we must act now. To do otherwise would be an abdication of our responsibility to future generations." Professor W.Wallace Covington, Journal of Forestry, August 2000.
Ecologically based restoration is the most effective approach we can take to reestablish the ecological integrity, or completeness, of the forest while protecting human communities. It is an approach that is informed by science and establishes as its primary goal the restoration of fully functional ecosystems that are linked to sustainable use by humans. Ecological restoration is not a recipe for ecosystem management. Rather, it is a broad conceptual framework for helping ecosystems recover more nearly natural structure and function while providing for continued use by humans. For ecological restoration to proceed on sound scientific footing, it must be rooted in the best knowledge available, with carefully reasoned analysis, checked against factual evidence.
Frequently Asked Questions
Why can't we just let nature take its course?
What is the "pre-settlement model"?
Does the treatment remove trees?
Does the treatment remove old-growth trees?
Aren't more trees better than fewer trees?
Is this a single treatment that will work everywhere?
What is the effect of restoration treatments on northern goshawks?
How do ecologically based restoration treatments reduce the threat of catastrophic wildfire?
Do treatments promote the spread of invasive plants?
Are restoration treatments aesthetically pleasing?
Why can't we just let nature take its course?
More than a century of severe habitat alteration has changed our forests to such an extent that they can no longer heal themselves. The catastrophic crown fires that have become more prevalent in modern times don't maintain ponderosa pine forests, but rather destroy them, leaving few living trees and threatening human lives and property. Such fires degrade wildlife habitat, alter soil composition, and cause soil erosion. Without restoration, we can expect more and larger forest fires.
What is the "pre-settlement model"?
The "pre-settlement model" is the name given by others to the ecologically-based, ponderosa pine forest restoration treatments developed by Dr. W. Wallace Covington and his colleagues at the Ecological Restoration Institute (ERI) at Northern Arizona University. The goals of ecological restoration in the ponderosa pine forest are to approximate natural ecosystem structure (plant and animal compositions and patterns) and processes (e.g. disturbance regimes such as fire, nutrient cycling, and productivity) that were characteristic of ponderosa pine forest before disruption by Euro-American settlement. These natural ecosystem structures and processes are critical for maintaining an ecologically sustainable forest and restoring the diversity of wildlife and plants that depend on it. The model is based on rigorous science and incorporates some of the longest-running ecosystem monitoring data, inventory, and research (begun in 1908) that exists in the United States.
An ecologically based treatment is site specific. In all treatments, trees that pre-date the settlement period are conserved and protected. Evidences of missing pre-European settlement trees (stumps, logs, stump holes, etc.) are used to determine the number of additional trees to be retained. Based on the number of trees that are determined to have been at the site, existing trees are retained to replace the missing trees. Additional trees are left to compensate for possible mortality immediately following treatments, to provide for special wildlife cover, and to accommodate specific ecosystem management needs (e.g. to provide a visual screen from roads). Emerging research is validating the accuracy of using pre-European evidence to replicate the natural forest structure.
Does the treatment remove trees?
Yes. Historic evidence and research show that the ponderosa pine forest of the 1860s had approximately 20 to 60 trees per acre (greater than 4 inches dbh, or diameter at breast height). Currently, there are typically several hundred trees per acre with some sites at several thousand trees per acre. This high density of trees contributes to the degradation of ecosystem health, increases old-growth mortality, causes declines in native wildlife and plant diversity, and leads to catastrophic crown fire. To restore the forest some trees must be thinned (the vast majority between 1-12 inches dbh). In some cases as many as 80 to 95 percent of the trees are removed (removing 80% of the trees at a 2000 tree/acre site leaves 400 trees, which is still beyond the pre-European settlement condition of the forest in some cases).
Does the treatment remove old-growth trees?
No. One of the goals of the treatments is to protect and restore vigor to old-growth trees. Research shows that the few remaining old-growth trees are dying at an unprecedented rate and that competition from small trees is the principal contributing factor. The treatment explicitly protects all old growth trees. At the Ft. Valley research site no trees over 16 inches dbh are removed. In other projects, where diameter limits are not in place, no trees established prior to European settlement are removed.
Is this commercial logging?
The restoration treatment is designed first and foremost to restore the ecological integrity of the forest. Commercial or industrial forestry interests do not motivate it. However, there may be appropriate commercial uses for restoration byproducts such as small-diameter trees.
Aren't more trees better than fewer trees?
No. In the southwestern ponderosa pine forest research shows there were, on average, between 20 to 60 trees per acre. Trees must be sufficiently thinned and spaced to allow reestablishment of native grasses and periodic low-intensity fires. Fewer, clumped trees allow grasses, wildflowers, and shrubs to become reestablished. It is the wide variety of plant life that existed in the pre-European settlement forest that will contribute to increases in the number and diversity of insects, mammals, birds, reptiles, and amphibians. Research has shown that there is a negative exponential relationship between tree density and herbaceous vegetation production; therefore, leaving excess trees can greatly decrease herbaceous production. In addition, inadequate thinning has the potential to increase the intensity of wildfire and undermine the goal of reintroducing low-intensity fires.
Is this a single treatment that will work everywhere?
No. At each location, site-specific treatments are developed to: 1. Approximate the range of conditions that existed at that particular site prior to European settlement; 2. Accommodate habitat requirements for endangered, threatened and sensitive species; 3. Accommodate for other wildlife habitat needs; 4. Minimize risk of introducing exotic species; 5. Accommodate for a modern context (e.g. roads, recreation, and social factors).
Is wildlife considered?
Yes. One of the goals of ecologically based restoration is to restore the full suite of processes, functions, and plant and wildlife species that existed in the forest prior to European settlement. The needs of endangered, threatened, and sensitive species are explicitly considered. Research is beginning to demonstrate that ecologically based restoration treatments increase both the numbers of and diversity of plant and wildlife species. Biodiversity continues to decline in the degraded, modern-day ponderosa pine forest. Ecologically based restoration offers a comprehensive approach to conserving and restoring species.
What is the effect of restoration treatments on northern goshawks?
It's uncertain, but a small negative effect is possible. Northern goshawks are large, uncommon forest hawks that live in low numbers throughout southwestern ponderosa pine forests. The Forest Service classifies them as "sensitive," and has tailored some of its management strategies around the species' needs. Studies in unrestored forests indicate that goshawks prefer dense stands of large trees for both nesting and foraging. If these preferences persist in restored landscapes, restoration treatments may reduce goshawk numbers. However, historic documentation shows that goshawks were present in southwestern pine forests before significant modern alteration of forest structure began, suggesting that they may be able to live in a more open forest than they do today. Goshawks need large trees for nesting, and one of the goals of restoration is to ensure that large ponderosa pines will persist on the landscape well into the future.
In addition, restoration is but one forest management strategy, and it is carried out within a larger landscape matrix. While some restored areas will have an open structure, they will be adjacent to denser areas appropriate for wildlife nesting, feeding, and roosting. All management activities (including a decision not to restore a forest) have positive impacts on some species and negative impacts on others. Most such effects, including possible negative impacts on goshawks, are expected to be small, and appropriate landscape planning and monitoring can help ensure that they are as small as possible.
Does the treatment evolve?
Yes. Ecological restoration treatments developed by the Ecological Restoration Institute exemplify the adaptive management process by incorporating new scientific research, practical experience, and monitoring in the design of each prescription. The Ecological Restoration Institute is committed to constantly adapting and refining treatments to reflect new knowledge. In addition, the ERI is committed to conducting new research to analyze the effects of restoration at larger scales.
How do ecologically based restoration treatments reduce the threat of catastrophic wildfire?
Treated forests have the potential to reduce the intensity of and slow crown fires. The treatments restore the forest to a structure that will in many cases stop fire from moving through tree crowns and allow it to drop to the ground. Once landscape-level restoration has been implemented, forest communities will enjoy the dual benefits of protection from crown fire as well as the reestablishment of diverse forests.
Do treatments promote the spread of invasive plants?
Possibly. Numerous species of invasive plants have become established in northern Arizona, especially along roads, in popular recreation areas, and in other places where the soil is regularly disturbed. Some nonnative species, such as cheatgrass, spotted knapweed, and Dalmatian toadflax, have already done grave damage to southwestern ecological communities by outcompeting native plants while providing few benefits to wildlife. Such species have the potential to spread rapidly into any disturbed area, including forest sites that have been thinned and burned during restoration. While restoration treatments themselves are a form of disturbance, one of their primary purposes is to forestall the much greater negative impacts of severe fires, which can cause widespread death of native plants and landscape-scale introduction of invasive species.
Some simple steps, such as frequently washing vehicles and other equipment in order to remove inadvertently carried seeds, can help minimize the risk of spreading invasive species at treatment sites. In some places it may be possible to reestablish native plant communities through active planting and reseeding. More research is needed to determine precisely what factors most benefit native plant species, and a few such projects are currently underway at treatment sites.
Are restoration treatments aesthetically pleasing?
Not initially. Forest thinning and burning leads to disturbance and stumps in the forest. However, research in aesthetic perception by Dr. Terry Daniel has shown that aesthetic values actually increase after prescribed burning once herbaceous production increases and covers low-cut stumps. Further, recent research by Daniel indicated that scenic beauty evaluations were highest for open, park-like forest similar to those of pre-European settlement times than for varying combinations of pre-European settlement scenes with denser pole and/or sapling-sized trees. But the real issue is what forest should be left for future generations. The answer is a forest that is ecologically healthy, biologically rich, and fully functioning. It took 150 years to degrade the southwestern ponderosa pine forest. It will take more than one, five, or ten years to restore it. What is ugly today may be lush and beautiful for the next generation.
For further information contact:
This e-mail address is being protected from spambots. You need JavaScript enabled to view it - (928) 523-5697 at the Ecological Restoration Institute