Overview of the Use of Natural Variability Concepts in Managing Ecological Systems.

Abstract

Natural resource managers have used natural variability concepts sincethe early 1960s and are increasingly relying on these concepts tomaintain biological diversity, to restore ecosystems that have beenseverely altered, and as benchmarks for assessing anthropogenic change.Management use of natural variability relies on two concepts: that pastconditions and processes provide context and guidance for managingecological systems today, and that disturbance-driven spatial andtemporal variability is a vital attribute of nearly all ecologicalsystems. We review the use of these concepts for managing ecologicalsystems and landscapes.We conclude that natural variability concepts provide a framework forimproved understanding of ecological systems and the changes occurringin these systems, as well as for evaluating the consequences of proposedmanagement actions. Understanding the history of ecological systems(their past composition and structure, their spatial and temporalvariability, and the principal processes that influenced them) helpsmanagers set goals that are more likely to maintain and protectecological systems and meet the social values desired for an area. Untilwe significantly improve our understanding of ecological systems, thisknowledge of past ecosystem functioning is also one of the best meansfor predicting impacts to ecological systems today.These concepts can also be misused. No a priori time period or spatialextent should be used in defining natural variability. Specific goals,site-specific field data, inferences derived from data collectedelsewhere, simulation models, and explicitly stated value judgment allmust drive selection of the relevant time period and spatial extent usedin defining natural variability. Natural variability concepts offer anopportunity and a challenge for ecologists to provide relevantinformation and to collaborate with managers to improve the managementof ecological systems.