Climate change influences the ecological processes driving regional vegetation change. With the paleoecological and geomorphological perspective of Holocene history, it is apparent that each vegetation change interacting with the environment sets the conditions for the next vegetation change. Because of interactions between vegetation change and environment, particularly for nontree species, pinyon-juniper woodlands of the Great Basin represent multiple communities and ecosystems. Multiple successional stages occur in repetitive, but constantly changing, mosaics across the landscape. Tree expansion over the last 150 years has set up the conditions for the possible decline in woodland area from large fires over the next 150 years. To manage these woodlands, better definitions of what is woodland versus other communities are needed that account for their long-term patterns of change and interacting cycles of disturbance and succession.