The I / O approach is potentially well suited to such planning and management issues as environmental impact assessment and evaluation of alternate growth strategies, and may be applicable to development of optimum management policies. Application of I / O on an annual basis of two lakes. carbon budgets has shown, at least qualitatively, the insight that might be gained by using the approach. The first limitation may require using dynamic, rather than static, models under some conditions, while extension of the model to multivariate systems may be necessary to avoid the limitations of the widely used univariate model.