Systematic Simplification of Mechanistic Models

Models of environmental systems are often complex, reflecting the complexity of the systems they try and describe. This complexity is difficult to manage and, especially in the face of limited observed data, there is a risk that models become over-parameterised with the result that predictions are less reliable than they need be. An approach to investigating the influence of model complexity on prediction accuracy is to compare the performance of alternative (simpler) model formulations. However this is difficult to achieve in practice as the process of simplification can be time-consuming with the consequence that only a few alternative formulations can be investigated. Automatic, or perhaps semi-automatic, methods of model simplification are potentially useful in addressing this problem. This papers makes the case for such methods and discusses some of the issues arising from their use, with a practical example for a mechanistic model of plant uptake of radiocaesium