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Management Situation by Revision Topic -" Biodiversity is composed of three primary components: composition, structure, and function. Composition refers to naming the elements. For example, making lists of species on the Rio Grande National Forest (RGNF). Structure is the physical arrangement of community complexity and the landscape patchiness pattern. Function is evolutionary and ecological processes that includes nutrient cycling, disturbances, and gene flow (Noss 1990). Biodiversity combines the variety of the physical environment with the variety of the biological environment. Both these environments are influenced by the social and/or human environments. The physical environment is climate, topography, soils, and geology. Climate is the most variable of these over a human lifetime. Weather cycles, windstorms, and atmospheric instability can vary widely from year to year. Eventually the climate tends to fluctuate within a general range to form a predictable weather pattern in an area. The biological environment is composed of the pool of -available species which successfully compete for existence in an area. This includes the full complement of living organisms --from inconspicuous soil bacteria and fungi, to the more visible plants, fish, birds, and mammals. The variety of living organisms is enormous. ;'j ,'" Biodiversity fluctuates over time and space, and scale is an important consideration. From genes and species to ecosystems and landscapes, there is an inherent ability for each level to cope with change. This adaptability to change is visually evident through the vegetation patterns on the RGNF today. Extensive aspen stands bear witness that natural fires have historically burned large areas of the RGNF. In fact, the RGNF is probably quite resilient to natural burning. When considering other types of disturbances, it is not as clear, but the RGNF is probably capable of withstanding considerable change. The last major climate change occurred with the closing of the last Ice Age -- about 10,000 years ago. Since then, the climate has reached a new equilibrium within a relatively predictable range of fluctuation. This degree of repetitive, predictable fluctuation is reflected in the plants and animals seen on the landscape today. Only those organisms adapted to exist within the normal environmental fluctuation can successfully remain here. Another area of biodiversity change is in the pool of available animals and plants. The introduction of exotic species changes biodiversity. Some exotics have been intentionally introduced while others escaped from intended, or unintended, introductions. Thus, biodiversity changes with disturbance, climate fluctuations, and species migrations, and extinctions. Biodiversity has fluctuated in the past and it will continue to change in the future. It does not and cannot remain static. Humans have modified the environment and, in effect, modified biodiversity in the past for short-term economic values. Social values are changing toward valuing larger tracts of public land managed to protect biodiversity (Probst and Crow 1991). Biodiversity should be conserved, but national forests also must provide a variety of sustainable goods and services to satisfy social needs. Since biodiversity is not static, choices made for management of the RGNF are relevant. Unfortunately, it is difficult, to get complete social agreement on priorities' for conserving biodiversity. Biodiversity is so complex that complete agreement may not be possible. Perhaps appeals and litigation of Forest Service decisions reflect society's disagreement over the expression of biodiversity on the national forests. Every land use action taken on the RGNF changes biodiversity. Conserving biodiversity and managing for multiple use means choices have to be made. It means goals for each action need 11I-7 -\ '~l" / -'"\ l, ,. ~ ;". V