Abstract:
A major issue in cumulative effect assessment (CEA) of marine systems (i.e., any component of the marine environment) is to inform relevant stakeholders on the assessment outcomes when faced with data and knowledge (collectively termed evidence) limitations. Evidence limitations can lead to an over simplification of marine issues, and consequently poorly informed management decisions. In order to address this major issue, this thesis applied a borrowed technique (i.e., forensic profiling technique [FPT] – developed for criminal investigators) to shed light on three uncertain areas: first, the current and future state of an estuary; second, to gain clarity on the disappearance of a keystone species from a benthic ecosystem; third, to identify the ecological implications (downstream effects) of this disappearance. The investigation outcomes (IO) suggest that multiple culprits (i.e., cumulative effects) are responsible for the current estuarine state, and were responsible for the keystone species disappearance and consequently the downstream effects of this. In addition, the IO suggest that CEA researchers need to think ‘outside the box’ and veer away from a one size fits all approach. This becomes apparent from the different methods of assessment employed in this thesis; i.e., a top-down approach was used to determine the state of an estuarine system, while a bottom-up approach was used to obtain clarity on the disappearance of a keystone species. The method of assessment is important in informing on the IO; more specifically identifying the risk and ensuring proper controls are put in place to manage these risks. This thesis highlights two management strategies that when implemented, can ensure risk is mitigated so that marine systems can return to a more natural state and/or ecosystem functions and services are preserved.
