10
Effective Ecological Modeling for
Use in Management Decisions:
Data Issues
David Hohler, Tom Ashwood, John R. Richardson,
Lisa Mai Olsen, Noble Hendrix, and Alison Williams
180
10.1 Introduction: How Data Are Used in Models
Data are used throughout the modeling process, from initial identification
of the question(s) to model testing and refinement. Although the nature of
a specific model or set of models will determine the data required and the
manner in which data are used, the following discussion provides general
insights into the fundamental role of data in the modeling process. Our
purpose here is to describe the different roles of data, discuss criteria to
judge the appropriateness of data for a model, suggest that the process of
data collection and use is iterative, and emphasize the necessity of disclosing the limitations of the data and models (Figure 10.1).
Brooks (1997) suggests a process for developing habitat-suitability-index
models that may be generalized to virtually all resource models. He identifies four primary phases: development, calibration, verification, and validation. More recently, Guisan and Zimmerman (2000) suggest a similar
process for habitat distribution models. Their four steps include: conceptual
model, statistical formulation, calibration, and predictions that are tested
against an evaluation data set. Similarly, we suggest there are five fundamental ways in which data are used in the modeling process:
1. formulation of the initial questions
2. development of the conceptual model
3. construction of the model
4. calibration/verification of the model
5. testing of the model.
10.1.1 What Is the Question?
The first question that a manager should ask before beginning a modeling
exercise is “What are the specific science and management questions that
are to be answered?” Clarity regarding the kind of information needed to
assist the decision-making process will improve the decisions and should
Effective Ecological Modeling for
Use in Management Decisions:
Data Issues
David Hohler, Tom Ashwood, John R. Richardson,
Lisa Mai Olsen, Noble Hendrix, and Alison Williams
180
10.1 Introduction: How Data Are Used in Models
Data are used throughout the modeling process, from initial identification
of the question(s) to model testing and refinement. Although the nature of
a specific model or set of models will determine the data required and the
manner in which data are used, the following discussion provides general
insights into the fundamental role of data in the modeling process. Our
purpose here is to describe the different roles of data, discuss criteria to
judge the appropriateness of data for a model, suggest that the process of
data collection and use is iterative, and emphasize the necessity of disclosing the limitations of the data and models (Figure 10.1).
Brooks (1997) suggests a process for developing habitat-suitability-index
models that may be generalized to virtually all resource models. He identifies four primary phases: development, calibration, verification, and validation. More recently, Guisan and Zimmerman (2000) suggest a similar
process for habitat distribution models. Their four steps include: conceptual
model, statistical formulation, calibration, and predictions that are tested
against an evaluation data set. Similarly, we suggest there are five fundamental ways in which data are used in the modeling process:
1. formulation of the initial questions
2. development of the conceptual model
3. construction of the model
4. calibration/verification of the model
5. testing of the model.
10.1.1 What Is the Question?
The first question that a manager should ask before beginning a modeling
exercise is “What are the specific science and management questions that
are to be answered?” Clarity regarding the kind of information needed to
assist the decision-making process will improve the decisions and should