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Ecosystem, Land, and Forest Health

Herein we believe that we provide an important step in discussing forest health. Many steps are needed because of the complexity and importance of the topic. The discussion is needed partly because of general interest and the pleasure of discussing complex topics. Equally important, it is needed as a basis for understanding legal action claiming that forest health should be maintained or improved, or as a basis for aggressively defending against those who may claim or exercise injunctions because of a premise that such forest health has not been maintained or improved. We seek to clarify further the concept of ecosystem, land, and resource health as seen by many thoughtful landowners.

Ecosystem health has been difficult to define and many people have tried to do so. Combining "ecosystem" and "health" with "land" also creates difficulties, but other people have tried. The phrase is partially for general conversation; it has an intuitive appeal and common understanding. Moving it beyond general conversations, ecosystem health needs to be defined so that people can tell when it occurs or how to change things so that it will occur. By its connotation it is a desirable condition, and we ought to be able to describe it if we really understand it. We ought to be able to decide when we have it. It may be a condition which, if it can be quantified, may be an overall system performance measure.

Other expositions on forest or other land use health include phrases like "fully functioning", "in balance", "resilient to change", "ecological integrity", "free-from-distress syndrome", and "sustained complexity", and "self-renewal." These words or phrases are unclear and themselves difficult to define. Thus, they provide little basis upon which to gain agreement and no basis for work. Some foresters say forests are healthy if there is a balance between growth and mortality. This may be true at a multi-state scale but it does not add to clarification and suggests that at least one problem in definition results from discussions at different levels of interest.

Surprising to some people, forest health has been narrowly limited to topics of insect and disease conditions and programs limited to surveying and monitoring such conditions, then contracting for suppression action. Topics include outbreaks of native pests, introduction of exotics (including plants), and research.

We admire the land health concept presented by Leopold. It spoke of land "sickness" as erosion and other abuses, of restoration, and of natural areas representing "well" land. The health of all types of wildlands has been a concern of the public and land managers since before Aldo Leopold wrote of land health in 1949. Since then, in the early 1990's, concerns about it were repeatedly voiced and the topic of forest health became a component of a range of concerns and strategies that were variously termed "new perspectives", "ecosystem management", "biodiversity", and "sustainable forestry." Kolb and others in 1994 said that a definition was needed, for without one, applying the concept was difficult. They noted that considerable clarity is needed when a healthy forest or other land use type is viewed as a constraint on uses and management actions.

The U.S. Congress in 1988 directed the U.S. Forest Service to

" ... conduct such surveys as are necessary to monitor long-term trends in the health and productivity of domestic forest ecosystems."

A planning issue for southern National Forests (1997) was said to be

"what conditions are needed to maintain forest capacity to persist and perform as expected or desired? Of particular concern are the impacts of exotic or non-native species; and the presence of ecological conditions with a higher level of insect and disease susceptibility,"

The "issue" and concern seems little more than that of productivity and we are not sure why it needs to be phrased in terms of health.
Giles worked with concepts of human health and GIS applications to human health data for many years. He believed that there were strong similarities between human (his sketch here) and wildland health (also discussed by Aldo Leopold).

Kessler (1992:20) said that "today, however, public reaction to proposed management may not reflect preferences among competing uses so much as perceptions of how proposed actions will contribute to or detract from the "wellness" of public lands, ecological systems, and the global environment. This calls for a new paradigm concerned first and foremost with the ecological health and condition of forests, and secondarily with the products they yield for human use."

Why foresters started intensive discussions of forest health in the 1990's is unknown. They should have known better; health is a word having been debated for centuries. The word and associated concepts can only lead to discussions, frustrations, and anxieties unlikely to be resolved either for human or forest health. Nevertheless, the word has been spoken, the spirit is out of the bag, and a statement approximating the concept used in Lasting Forests seems necessary, if not appropriate.

Within the region we have developed a concept of land health because there are many types of land, in addition to those that are forested. We try to make the concept more useful at a smaller scale, retaining that perspective.

Management Objective

We see his general outline to be success in maintaining the sustainability of ecological conditions and processes in conserving the ecological integrity or co-evolved diversity of land.

Health, like other words, is useful in general conversations but is not a scientific word with a precise definition. Thus, we have several points of view, some apparently at great distance from others. If the "health is when management objectives are achieved" view is taken, even then conflicts arise because people may have different objectives for the same tract of land. Health becomes "whatever I say it is!" A ponderosa pine stand without dwarf mistletoe will have reduced wood growth; the same area with mistletoe will have more birds. When there is only one objective (a rare case) this definition of health works well. Other definitions create problems. An example is: health is a condition where biotic and abiotic influences on forests and similar lands (e.g., insect and wildlife pests, air and water pollution, storm events, drought, fire, pathogens, silvicultural treatments, harvesting) do not threaten management objectives. In other words, a land is healthy if it achieves management objectives. As Kolb and co-authors point out, there is a danger in the logic here. If a healthy forest is, itself, a management objective, and if a healthy forest meets management objectives, we have the circular condition: a desired state of forest health depends on the occurrence of a healthy forest.

Lasting Forests staff has worked on human health analyses for years. The analogies between human and forest health are clear. We have reviewed dozens of papers defining and describing health and have come to a unique definition likely to benefit all fields in which it is used. It is:

Forest health is a condition of groups of trees existing along a life continuum from" excellent" to" very bad." (the instant before death). It is a word that should not be used without a descriptive word such as "individual "or" population." Optimum health is the homeostatic condition for a stage of life from which a population achieves its growth, reproductive, or transition potential for the next stage and for the greatest number of subsequent years (at least twice the current life expectancy of the total population).

Lack of Disturbance?

Recent U.S. Forest Service policy has emphasized the values of sustainability, biodiversity, productivity, and forest health, conditions rather than particular deliverable products. Disturbance ecology (Rogers 1996) is a phrase that has replaced or joined the literature on "anthropogenic effects" of various factors on ecosystems. From one perspective these are health topics. They identify the stressor, the stress, the evidence of the stress, and suggest whether it has past a point at which it is judged bad, unacceptable, or a condition of "disease" or being "unhealthy." Whether pathogens or forest fires are natural, expected, or normal is part of the controversy opened by such phrases as "disturbance ecology." Perhaps a small lightning fire is not a disturbance. Is a disturbance anything that causes a change in a system? Is addition by growth of a forest stand, say of 100 m3, a greater disturbance than loss of 100 m3 to insects? Is the system, if disturbed, unhealthy? Rogers acknowledged the looseness of past definitions of disturbance ecology and equivocated with a study of distinct events that disrupt the function of ecosystems. "Disturbance", therefore, competes with "disrupt" for clarification and there is little more clarity. Rarely are areas or systems smaller than a pond or forest "gap" (a hole in a forest canopy resulting from death and/or removal of a tree). When very large systems are used as the topic of interest, small changes "average out" or "balance." The larger the ecosystem selected, the less likely it is to be seen as "disrupted," perhaps "unhealthy." The same is true for the period of study. A change in an area may appear profound for a day, immaterial over a 100-year timber rotation.

"Disturbance" connotes that there is an answer to "from what?" Ecologists typically deal with equilibrium or non-equilibrium debates. These hinge upon the period of the study (e.g., the stability of a forest for 10 years or 1000 years). The range of variability is crucial, both that which occurs and the tolerable limits set by humans as "excessive" or "dire shortages!"

Rogers (1996) listed disturbance agents as abiotic: winds, droughts, fires, and gravity and geomorphology; and biotic: insects, disease, grazing, and human system uses. These are the stressors of disease systems, a small list that may be expanded to assist in "forest health" work as well as other advances in the concept of land health ... or its replacement (as inadequate for analyzing and solving problems of the human for the future).

"Health" as a concept has now become entwined with words like "stressors" implying drought or moisture. An insect may also be considered a stressor but a forest after an insect attack looks bad, unhealthy. Lands losing species certainly cannot be viewed as a "healthy situation." Populations that cannot reproduce themselves (because of dams preventing return to spawning areas) are viewed as unhealthy although the fish themselves are perfectly healthy. Controversy rages over whether areas with excessive fuel loads and in danger of modern forest fires are healthy.

Resilient

One Forest Service report suggests being healthy is an expression of "resiliency." Whether a county and its socioeconomic status are one of resiliency allows health to enter another field of analysis. Somewhere else "ecological integrity" enters along with "resiliency," is an expression of species not lost and those not about to be lost (thus "threatened and endangered" and protected by law). Wholeness and resiliency compose integrity, probably health.

"Resilient" or ability to rebound from normal disturbance is often listed as a characteristic of health but perhaps that is health itself. It is not a readily observed physical phenomenon like the above-listed item.

Rangelands that are over-used are readily subject to weeds. Health or rangeland can be related, analogously, to the body's ability to withstand a pathogen. Rangeland workers define health as the degree to which the integrity of the soil and ecological processes of rangeland ecosystems are sustained. (This phrase requires simultaneous consistent agreement among discussants of the health topic about the problematic definition of five other words. Similarly, "healthy ecosystems" are perceived to meet society's social and economic needs better than other ecosystems.

Population or Individual?

Forest health has unusual dimensions but many are those of human health. A forest cannot be healthy in surroundings of unhealthy forests. There is a pubic-health dimension, one of forest populations rather than forests, stands, or trees. There is an extreme time dimension, one allowing a forest to be unhealthy today but to have recovered to a healthful status in one or two years. Of course, the relevance of either is closely tied to the held definition. One concept of health is merely one of continued high production of some commodity (like timber or pulp). Others, especially within Lasting Forests staff, insist on long-term profit production as the criterion of health, not merely wood produced.. They may be correlated but that is not guaranteed.

Another view of health is one of an assemblage of trees that are vigorously growing, accumulating biomass. Confusion begins to grow when someone insists that nutrient cycling must be rapid. This may be time for young forests (rapid gains) but few will argue that only young forests are healthy. Some will emphasize recycling of minerals and thus argue that this condition exists in the early climax condition of most ecosystems. Tree vigor or vitality is said to be high but agreement on the measure whether photosynthesis, annual increment, basal area increase, or net present value increase are all worthy of and present difficulties for debate.

"The absence of sickness" helps understand health not at all. A human disease like lupus, called "the disease of 1000 faces", is diagnosed when 4 of 11 symptoms are present. This may be a suitable algorithm for forest health, some number of conditions being present; absence of a condition not denying health.

Kolb and co-authors said that a quantitative approach to defining (and presumably estimating it) forest health may require years of research and monitoring. After hundreds of years, the medical profession has not yet agreed upon the definition of health, so we do not wish to move far along that costly, evidently contentious pathway. We prefer instead to suggest that we can recognize a healthy forest or land unit when we see one and name the ways that we recognize it. These are unified in a Lasting Forests health index, H, which, based in part on Kolb contains the relative extent to which a forest stand, pond, marsh or similar land unit meets the following weighted criteria. One meeting all criteria fully has an index of 100. Health is a relative, continuous, and dynamic concept, so it is reasonable to consider an area with an index greater than 80 as healthy.

The criteria in the index are:

  1. The physical components, biological components and feeding networks to support productive communities during at least some stages of expected ecological succession for a "type."
  2. Resistance to catastrophic change and ability to recover from such change at the landscape level.
  3. Functional equilibrium between inputs and exports (of any type) of essential resources (e.g., water, nutrients, energy, and growing space) for major portions of the vegetation and their fauna.
  4. Many stages of succession (age classes) and structures that provide the complex spaces and conditions for many native species.
  5. Many age classes with their associated conditions and ecosystem processes that assure the named "type" to be present in the landscape for at least 200 years.
  6. Normal or less soil loss.
  7. Normal or greater faunal species richness.
  8. Normal or less abundance of fauna in each taxa.

The index needs to be as suitable for analyzing a desert spring as an Alaskan alpine ridge, a longleaf tree stand, a bottomland hardwood stand, or a Spartina marsh.

The index needs to include concepts of normal demise and losses of early stages (often with associated disease, insects, and other stresses) that are natural precursors to later stages.

The index needs to include the context of the tract or stand. One tract may be "unhealthy and dying" as it is replaced by the expected, natural next stage, thus healthy as a regional or landscape scale. A dead tree may occur in an otherwise healthy stand and is valuable to some fauna.

The index is not restricted to concepts of pests or diseases. If any one of the components is judged to have a condition less than 20, the index becomes 20. If any one is score 100, the index becomes 95.

A land use unit (forest) at extreme risk of change (> 0.8) in less than 5 years in any one of the criteria (due to forest fire fuel build-up or other phenomena, not yet resulting in system changes) has an overall score reduced by at least 10%.

There is no intent within Lasting Forests that every land unit achieve a high health index. In general, the higher the better for all units, but changes have occurred in land units over hundreds of years. Some units like lawns, waste disposal areas, waterfowl feeding areas, winter-food production areas -- all require intensive work that likely prevent one or more of the criteria from being met. Most of the health index criteria or a surrogate are included in the stabilizing, long-range view taken in computing R and the current status of the land ownership.

Since the fundamental laws of biology are that living systems are to get energy, conserve energy, and reproduce, health occurs when these occur. Old age (as in ancient forests) may not be a healthy condition under these laws. Health may be the condition in which energy is processed competitively with effective mineral cycling, without blockages, accumulations, or shortages (Odum et al. 1970). Energy flow and nutrient cycling are absolutely coupled, but to know one is not to know the other. The usually-stated conditions for forest stand health include:

  1. stable or recovering plant richness
  2. stable or recovering animal richness
  3. stable or increasing nutrient capital (soil and foliar nutrition)
  4. high rate of nutrient cycling (minimum nutrient loss from the system)
  5. minimum soil erosion
  6. minimum disease (visual symptoms)
  7. minimum pest (visual symptoms)
  8. stable or increasing biomass (forest growth)
Lasting Forests staff do not look at factors or forces themselves as elements in health analyses. Fire may be bad for a forest, reduce its health, but it may also improve conditions and long-term forest health.

Identical fires in different periods may have very different effects in the same forest. A singular fire may effect an unhealthy forest very differently than a vigorous forest. Health is the condition to which stressor effect (fire, logging, pesticide, grazing, logging, road building, air pollution, and exotic insect attack) may be evaluated.

Trees and forests can survive and be productive despite the effects of pathogens and insects. These are temporary and not "bad health"; an organism in "good health" can recover quickly. Free of disease or "problems" is not, therefore, a statement of a healthful condition. Forest composition can be altered by "disease" events. Productivity can be reduced, either the rate of trees or the net growth (stable growth but with losses). Mortality can be increased. Health seems reflected in competitiveness of individuals. Stress factors need to be studied, but the forest stand itself is to be evaluated as healthy or not, a continuum of conditions.

The Edge of Death?

A very healthy person may die within 30 days. A doctor may tell a person that he will die within 30 days. Few would argue that such a person is healthy. Health then, contains the condition of having no predictable ill health or death. Health, however, need not be observable (as may be the case of the healthy-appearing person about to die.) Trees planted in the wrong place may appear vigorous and growing. If they will die at the first freeze below 10 degrees F are they healthy? The knowledgeable forester, aware of range limits, may have confidently said: "You will die within 30 years!"

H. J. Heikkenen's studies (pers. comm.) show that trees with bark beetles are previously water stressed (unhealthy) and are attacked by the insects after stress. They are not the cause of the unhealthy state. The cause-and-effect may be difficult to discriminate. Presence of an apparent pathogen (bark beetles) may signify not sickness but that death has already occurred. The perceived pathogen may simply be one of the decomposers.

Achieving land health (the health care " delivery" system or land management) includes preventing, diagnosing, controlling, and eradicating disease both for individual land units and for regions. It also includes predicting likely conditions--of both the causes of the " disease" as well as the symptoms--thus the research, monitoring, and managerial needs and costs.

Literature

The Forest Health Report is now available.

Brooks, R. T., T. S. Frieswyk, D. M. Griffith, E. Cooter, and L. Smith. 1992. The New England forest: baseline for New England forest health monitoring. U.S.D.A. For. Serv. Northeastern For. Exp. Sta., Res. Bull. NE-124, Radnor, PA. 89 pp.

Busby, R. E. and C. A. Cox. 1994. Rangeland health: new methods to classify, inventory, and monitor rangelands. Renewable Resource Journal 12(1):13-19.

Costanza, R. 1992. Toward an operational definition of health in Costanza, R., B. Norton, and B. Haskell. (eds.) Ecosystem health -- new goals for environmental management. Island Press, Washington, D.C.

Dahms, C.W., B.W. Geils 1997. An assessment of forest ecosystem health in the Southwest. USDA For. Serv., Rocky Mt. Forest and Range Exp. Sta.,Ft. Collins, CO. , Gen Tech Rept. RM-GTR-295, 97p.

Kaufman et al. 1994.

Kessler, W. B. 1992. A parable of paradigms: personal wellness and forest health. J. For. 90(4): 18-20.

Kolb, T. E., M. R. Wagner, and W. W. Covington. 1994. Concepts of forest health. J. For. 92(7): 10-15.

Leopold, A. 1994. A Sand County almanac and sketches here and there. Oxford Univ. Press, New York, NY. 228 pp.

National Research Council. 1994. Rangeland health: new methods to classify, inventory, and monitor rangelands. Washington, D. C.

Norton, B. G. 1991. Ecological health and sustainable resource management. p. 102-177 in R. Costanza ed. Ecological economics: the science and management of sustainability. Columbia Univ. Press, New York, NY.

Rapport, D. J. and S. B. Yazvenko. 1996. Ecosystem distress syndrome in ponderosa pine forests p. 3-9 in W. Covington and P. K. Wagner (tech. coordinators), Conf. on adaptive ecosystem restoration and management restoration of Cordilleran conifer landscapes of North America. Gen. Tech Rpt. RM-GTR-278. U.S.D.A. For. Service, Rocky Mt. Forest and Range Exp. Sta., Ft. Collins, CO. 91 pp.

Rogers, P. 1996. Disturbance ecology and forest management: a review of the literature. U.S.D.A. For. Service, Intermt. Research Station, Gen. Tech. Rpt. INT-GTR-336, Ogden, UT. 16 pp.

Steedman, R. J. 1994. Ecosystem health as a management goal. J. N. Am. Benthol. Soc. 13(4): 605-610.

Suter, Glenn W. II. 1993. A critique of ecosystem health concepts and indexes. Environmental Toxicology and Chemistry 12: 1533-1539.

White, W., P. Janiga, R. Pywell, J. Adams, Eric Smith, Terry Daniel, W. Kurz, D. Bernard, P. Bunnell, L. Greig, and C. Murray. 1994. Forest health technology 2000 Task Force report, U.S.F.S. Forest Pest Management, Methods Application Group, Ft. Collins, CO. 117 pp.

Wicklum, D. and W. Davies. 1995. Ecosystem health and integrity? Canadian Journal of Botany 73: 997-1000.

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