Change models build on the assessment phase by asking, “with this knowledge, how might the study area be changed?” This step involves sketching design alternatives on top of your data layers from the evaluation model (suitability analysis). This step generates more data that will be used to represent future conditions.
Impact models ask, “what differences might these changes cause?” Your answer to this question involves a quick evaluation of the impacts of each design alternative on landscape function. Thinking in systems, does your proposed change affect a part of the system, or an interconnection between parts? Does it change the function or purpose of the system? Is that desirable? This step generates information about the potential impacts of each alternative that stakeholders and decision makers will use to determine a preferred solution.