Risks to the Region’s values
9.3.7 Cumulative impacts
The assessments of individual risks presented in Figure 9.1 and Figure 9.2 do not take into account the cumulative impact of the threats on the Region’s ecosystem and heritage values. None of the threats operate in isolation. They are connected through the geographic areas in which they occur (Figure 9.6), the timeframes in which they act, and the habitats, species, ecosystem processes and heritage values they affect. Interactions between threats can have variable effects. Many of the threats considered in this report are likely to have synergistic effects, where the impact of two or more threats acting together is much worse than that expected from the sum of their individual impacts.14,15,16 An analysis of cumulative effects takes into account direct, indirect and consequential impacts and the incremental and compounding effects of these threats over time, including past, present and reasonably foreseeable future pressures. The independent assessment of management effectiveness17 for the Outlook Report 2009 identified the extent to which cumulative impacts are being addressed as the weakest indicator across the entire management effectiveness assessment. It concluded that management effectiveness challenges were most evident for those issues which were broad in scale and complex socially, biophysically and jurisdictionally. The independent assessment of management effectiveness for this report (Chapter 7) highlighted that managing agencies’ understanding of cumulative and consequential impacts is improving, although this remains problematic for most issues especially in achieving outcomes for fishing. There are several ways to consider the cumulative effect of threats upon the Region’s ecosystem or heritage values. It largely depends on the context for which the examination is occurring and the amount of evidence available for the assessment. Methods range from modelling approaches that use simple, unstructured lists to quantitative mathematical models or spatial approaches that focus on a specific location or component of the ecosystem.
Figure 9.6 Example of multiple threats to the ecosystem within an area
Multiple threats, including those presenting high and very high risks to the Region’s values, can overlap and interact within an area. They combine to present a serious cumulative risk to local habitats and species.