 |
Overviews 
Overview by Chip McConnaha |
| Ecosystem Diagnosis and Treatment (EDT) is an analytical tool relating
habitat features and biological performance to support fish and wildlife
planning. It captures a wide range of information and makes it accessible
to planners, decision-makers and scientists as a working hypothesis of the
ecosystem. EDT acts as an analytical framework that brings together
information from empirical observation, local experts, other models and
analysis.
EDT differs from models often used in fish and wildlife management and offers important features that can augment conventional methods. EDT is best described as a scientific model (see Hilborn and Mangel, The Ecological Detective). A scientific model attempts to explain the mechanisms behind phenomenon to form an overall hypothesis. This contrasts with more conventional statistical models. These provide correlation-based predictions of events without necessarily explaining the underlying mechanism. As a scientific model, EDT constructs a working hypothesis of a subbasin as a basis for planning and for comparison of alternative futures. This hypothesis provides measurable metrics to gauge progress and testable hypotheses to refine knowledge. EDT helps us understand and describe the inevitable complexity of ecological systems in order to plan effective recovery strategies. A statistical model, on the other hand, seeks to reduce complexity to a small number of predictive or correlated variables. A scientific model like EDT provides the hypothesis while a statistical model can provide the test. The premise of EDT is simple: habitat forms the template for biological performance. Species perceive habitat based on their genetically based potential. The result is species abundance, productivity, diversity and population structure. Although EDT can become complicated due to the fine-scale complexity of its ecological description, it is important to bear in mind the underlying simplicity of its premise. EDT has two major components: a detailed description of the habitat and a set of rules or hypotheses that define an understanding of how a species perceives or responds to that habitat. The environment is described by 45 biologically significant attributes that relate to a specific habitat unit such as a HUC (Hydrologic Unit Code) segment. The rules describe the species perception of the environment in terms of life stage productivity and capacity as a density dependant Beverton-Holt relationship. Integrating over a life history trajectory provides population abundance, productivity and diversity. The environmental attributes and rules in EDT provide, respectively, monitoring attributes and research hypotheses. This provides a framework for accountability, monitoring and research. The environmental description and rules within EDT can be developed and tested through a variety of statistical models and research. In this way, EDT presents a scientifically based framework for natural resources planning and action. |