historical range of variability

For more than a century ecosystems around the world have experienced an increase in the dominance of woody species. While the drivers of woody plant proliferation are complex, interactions between climate and land-use change are commonly invoked as primary contributing factors.

Reference ecological conditions offer important context for land managers as they assess the condition of their landscapes and provide benchmarks for desired future conditions. State-and-transition simulation models (STSMs) are commonly used to estimate reference conditions that can be used to evaluate current ecosystem conditions and to guide land management decisions and activities.

The concept of historic range of variability (HRV) is briefly evaluatedwithin the context of its application in ecosystem managementover the past two decades. Despite caveats to the contrary, animplicit assumption continues to emerge of climatic stationarity,and, by corollary, that presettlement centuries provide an appropriatereference period.

As climate models improve, decision-makers' expectations for accurate climate predictions are growing. Natural climate variability, however, poses inherent limits to climate predictability and the related goal of adaptation guidance in many places, as illustrated here for North America.