Historic range of variability is a method to understand the dynamic nature of ecosystems; the processes that sustain and change ecosystems; the current state of the ecosystem in relationship to the past; and the possible ranges of conditions that are feasible to maintain. It is a useful tool for determining a range of desired future conditions, and for establishing the limits of acceptable change. Best available science and local management expertise are used to determine the historic range of variability.
Once the Historic Range of Variability is established for an area, it can be compared to existing vegetative conditions to determine departures. These departures can be used to aid resource managers in the planning of their treatments.
An example of an existing vegetation mosaic map used to profile current conditions. Maps such as this were used to compare existing conditions versus desired conditions in the Spring Creek and Dry Creek watersheds on the Uncompahgre Plateau.