Feedback analysis in reserve management: studying local myths using qualitative models

A qualitative modelling approach is used to highlight potential feedback mechanisms and secondary effects of management actions on a number of key species in a large Argentine wetland. The development of this qualitative model, in this case a loop model, was a first step in the creation of an overall management and monitoring programme for this important wetland. The use of loop models is a possible strategy in environmental management and monitoring programmes of large complex natural reserves, in which little quantitative data is available. Based upon observed ecological information, several loop trophic models were constructed and appropriate links made to reflect actual trophic relationships between trophic variables. The potential secondary effects of a hunting ban on caiman in a large shallow lagoon were examined. Indirect secondary effects were found to produce unforeseen negative impacts on other predator species (piscivorous birds, piranha) and species important to the abiotic environment (large bottom dwelling fish). As there are limited quantitative data, field investigations and the development of other types of models are necessary to examine in detail the quantitative variations on the populations in question. The results of this model were found useful to indicate where further study and quantitative data gathering might be best focused.