Use of models for detecting and monitoring change in a mangrove ecosystem in Northwestern Australia

Abstract

A monitoring programme to detect effects of solar salt ponds on mangroves in north-western Australia is described. Sites were established in different mangrove communities at five locations, two of which were modified by salt ponds and the other three used as references. A conceptual model was developed to identify potential changes to the mangrove ecosystem next to ponds, to identify responses to change and to formulate a null hypothesis to test that ponds have no effect on vegetation structure. A simulation model using real data was developed to evaluate power of tests of the null hypothesis for nominated levels of change in mangrove stem density and leaf area index (LAI). These attributes were too variable to provide powerful tests of the null hypothesis and this component was discontinued. Changes in groundwater salinity and LAI monitored at the five locations between 1992 and 1995 are presented to demonstrate the similarity in behaviour of these attributes at modified and unmodified locations. Results of monitoring a localised disturbance to the mangrove system next to one pond are presented to demonstrate how the disturbance was tracked through monitoring and how the mangrove responses to that disturbance conformed with those predicted in the conceptual model.