HOLISTIC APPROACH TO ECOLOGICAL MODELING

Models of different complexity were used to examine how the ecological buffer capacity, β (defined as the change in loading relative to the change in a considered state variable) varies when the loading, e.g. the input of phosphorus, is changed. It was found that while β = ΔP(total)/ΔP(soluble) increases with increasing complexity of the model at low P-loading, the β-value will - at medium P-loadings - have a maximum value at a certain degree of complexity, and will be a decreasing function of complexity at high phosphorus loadings. This might explain why very eutrophic lakes, rivers polluted with organic matter or other stressed ecosystems are stable although their complexity is low. The more complex ecosystems seem best able to cope with increasing variations in climatic factors. In the models considered the thermodynamic function exergy correlates well with the sum of relevant buffer capacities. High exergy levels mean that the structure is more able to meet changes in external factors. © 1979.