Separate risk assessments are presented for the Region’s ecosystem (natural heritage value) and heritage (Indigenous, historic and other) values. The Australian Standard was followed for risk management (AS ISO 31000).2151 The likelihood and consequence of each threat is ranked on the five-point scale set out in Appendix 7. The criteria for selecting a consequence level differs between ecosystem and heritage values. An overall risk level for each threat is determined by applying a risk matrix that combines its likelihood and consequence.
The risk assessment for each threat is based on effectiveness of existing management measures so the overall risk rating is considered the residual risk. For example, the risk levels for climate change related threats are based on the current policy environment and commitments to emissions reduction. The assessment is based on information in Chapters 2 to 8 of this report, including the current state and resilience of the Region’s ecosystem and heritage values, major factors influencing the Region’s values (including human use) and effectiveness of management. Further input on risk levels was sought from experts both external 12 and internal to the Reef Authority.
Due to the size and complexity of the Region, this assessment is high level because many threats, which interact in different ways, affect its values over varying time and spatial scales, at different intensities. The assessment is based on the following considerations:
- Each threat was initially assessed in isolation from others; cumulative impacts are discussed separately (Section 9.3.7)
- Each threat was assumed to be possible at any geographic location within or, where relevant, adjacent to the Region
- Threats were assessed as they were at the end of 2023 (for example, current fishing techniques and catch amounts) or on the basis of documented trends (for example, trends in sea temperature and ocean acidification)
- Threats were assessed in consideration of existing management measures only. The mitigating effect of any future management measures were not considered
- Threats were assessed in consideration of the effectiveness of existing management measures
(Chapter 7).
In understanding the consequence of a threat to the ecosystem (natural heritage value), variations in the extent of the threat’s likely effect were taken into account through different criteria for broadscale and local-scale effects (Appendix 7). In order to understand the true level of risk for each threat, the higher consequence grade is adopted in determining the overall risk. For heritage values (Indigenous, historic and other), consequence level is considered using a single criterion that encapsulates both the geographic scale of effects and the range of heritage values affected (Appendix 7).
