Annotated Texts
Forest health is an increasingly important concept in natural resource management and international discussion. The term 'forest' health is, however, difficult to define as definitions depend on human perspective. While the term itself is relatively new in forestry, notions of forest health were included among others in the writings of Aldo Leopold (1887-1948) and others before him. In several of his essays Leopold described widespread symptoms of 'sickness' such as reductions in vegetation cover and soil erosion. He argued for the practice of land health in which practitioners would seek to maintain the sustainability of ecological conditions and processes by conserving the ecological integrity of the land. (Flader 1974; Kolb, Wagner, Covington 1995).
More recent views range between utilitarian and ecosystem perspectives. The utilitarian perspective focuses on forest conditions that directly satisfy human needs. From a utilitarian perspective forest health can be defined as "a condition where biotic and abiotic influences on forests (pests, pollution, silvicultural treatments, harvesting) do not threaten management objectives now or in the future" (McIntrie 1988, USDA 1933a). A forest is, thus, considered healthy if management objectives can be satisfied. While such a definition may be appropriate for private industrial forests with unambiguous management objectives such a definition is difficult to apply to forest lands managed for multiple purposes given that there are additional objectives such as species diversity etc.
As most forests have multiple uses several forest health definitions from the ecosystem perspective have been developed. Examples for these definitions are "a forest in good health is a fully functioning community of plants and animals in their physical environment" (Morning and Byler 1992) or "a healthy forest is one that is resilient to changes" (Joseph et.al 1991). As some elements of these and other ecocentric definitions are hard to define and to measure (e.g. resilience is difficult to quantify as the degree of resilience is usually only known after the forest has been exposed to stresses). Quantitive approaches to defining and measuring forest health are thus sometimes problematic. Another potential problem with the quantitive approach to defining forest health are according to Kolb, Wagner and Covington the costs associated with monitoring and the collection of scientific reference data. Kolb, Covington and Wagner suggest, thus, that "in the absence of quantitative information on desired rates of ecosystem processes" qualitative statements should be included in forest health definitions from the ecosystem perspective. They suggest to consider a healthy forest ecosystem to have the following characteristics: 1) physical environment, biotic resources and trophic networks to support productive forests during at least some seral stages, 2) resistance to dramatic change in populations of important organisms within the ecosystem, 3) a functional equilibrium between supply and demand of essential resources (water, nutrients, light, space) and 4) diversity in seral stages, cover types and stand structures that provide habitat for many native species and all essential ecosystem]processes (Kolb, Wagner, Covington 1995).
The ambiguity about forest health is also to large parts caused by the fact that a concept developed at the individual level (health of an individual) is applied to complex systems such as forests or ecosystems. A dead tree e.g. is not healthy but it may be part of a healthy stand. Generally the ecosystem perspective is not necessarily in conflict with the utilitarian perspectice if "both are applied to large landscapes composed of a mosaic of different stand ages, structures, and levels of management intensity appropriate for satisfying the range of demands placed on the landscape by society". (Kolb, Wagner, Covington 1995).
Literature cited:
Colb, T.E.; Wagner, M.R.; Covington,W.W. Forest health from different perspectives. 1995 in Proceedings of the 1995 National Silviculture Workshop
Flader, S.L. 1974. Thinking like a mountain: Aldo Leopold and the evolution of an ecological attitude toward deer, wolves and forests. Univ. Missouri Press, 284 p
Morning, E.; and Byler, J.; 1992 Forest health and ecological integrity in the northern Rockies. USDA Forest Service Rep.
