IV. TRANSFERABILITY OF ECOSYSTEM MODELS 



It is recognized that, for several reasons, it is desirable to have models 

 that are usable for a variety of different sites and environmental conditions. 

 These reasons include reduced development costs and increased confidence in the 

 robustness of model outputs. However, it must be strongly emphasized that 

 modeling is strongest when designed and tuned to answer quite specific questions 

 for particular configurations of biotic and abiotic assemblages. As a minimum, 

 the structure and assumptions built into each model must be re-examined each 

 time it is used to ensure that they are still appropriate. While processes and 

 interrelationships may be translocated, the specific rates and state variables 

 may not be. This would be particularly true where species composition or genera 

 are different at the new modeled site. Blind reuse of existing models invites 

 results which are at best inappropriate and at worst seriously erroneous. To 

 prevent this, model users (managers) should avoid translocation of models 

 without the direct involvement of scientists and model builders to re-verify 

 the model design and implementation. In short, if participants take seriously 

 the hypothetical and experimental nature of models and the need for continuous 

 communication among modelers and management, attempts to apply existing models 

 to different ecosystems or even to different problems in the same system will be 

 done only with careful evaluation of the model's strengths and limitations. 



V. TRANSLATION FROM ECOSYSTEM MODELING RESULTS TO ENVIRONMENTAL QUALITY CRITERIA 



Ecosystem models can be powerful environmental assessment tools. In theory 

 they allow evaluation of more than one quality criterion at the same time and 

 allow indirect as well as direct effects to be determined. Considering their 

 potential, ecosystem models can be more fully utilized in environmental 

 assessment. 



One problem is that ecosystem models often produce results that managers 

 have difficulty using. The methodology for making ecosystem models more 

 meaningful to environmental assessment requires further development. Different 

 types of modeling results applicable to environmental assessment needs must be 

 identified and their relevance explained to managers so that they will understand 

 them and can determine what will be useful to them. A difficult, controversial, 

 but desirable goal is to translate ecosystem modeling results into terms that 

 can be used in cost-benefit analysis. 



Many complications will be encountered in any approach to quantify costs 

 and benefits. Some costs and benefits vary according to user, and optimum 

 balance between costs and benefits may not be the same from all perspectives. 

 For instance, increasing the primary productivity of a water body may be 

 desirable from a fisheries perspective but undesirable from the viewpoint of 

 recreational users of a water resource manager. Some costs and benefits are 

 not associated with any particular user group but rather with general quality 

 of life; although these are probably the most "valuable" to society, they are 

 the most difficult to quantify. A further complication of cost-benefit 

 calculations is that nonlinear relationships clearly exist. 



Quantifying environmental quality criteria in terms of economic value is a 

 problem not just for ecosystem modeling but for environmental assessment in 

 general. Only a few researchers in the country have attempted to address this 



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