Thresholds are important to understanding Great Basin ecology. Once a threshold has been crossed, the new community may have very different functional capabilities than the previous community. Management action needs to occur well before a threshold is crossed to be effective, and that action needs to reflect the scales of time and space in which the affected ecosystems and their thresholds function. Great Basin woodlands have at least three categories of thresholds, with two stages in the threshold process. The three categories of threshold differ in both the duration and timing by which the two stages of the threshold process occur. Depending on the community, more than one threshold may be involved in affecting community change at the same time. Thresholds interact between communities on landscape scales over the long term, often in response to climate change, and are most effectively managed on a landscape basis.