Grading statements — Ecosystem resilience
Under current management, throughout the ecosystem, populations of affected species are recovering well, at rates close to their maximum reproductive capacity. Affected habitats are recovering within expected natural timeframes, following natural cycles of regeneration.
Populations of affected species are recovering at rates below their maximum reproductive capacity. Recovery of affected habitats is slower than naturally expected but structure and function are ultimately restored within a reasonable timeframe.
Populations of affected species are recovering poorly, at rates well below their maximum reproductive capacity. Recovery of affected habitats is much slower than expected natural timeframes and the resultant habitat is substantially different.
Affected species are failing to recover and affected habitats are failing to recover to their natural structure and function.
or
Borderline Indicates where a component or criterion is considered close to satisfying the adjacent grading statement.
Confidence
Adequate high-quality evidence and high level of consensus
Limited evidence or limited consensus
Inferred, very limited evidence
Elements of the natural ecosystem have been severely affected by repeated mass bleaching events, heavy floods and marine pollution. These elements include coral reef habitats, dugong populations, and loggerhead turtles. The resilience of these species and communities is likely to be compromised. Recovery has been observed in seagrass meadows in the northern Region although the southern meadows are likely to be less resilient to future disturbances. Coral trout and black teatfish populations have also shown signs of recovery. It is projected that humpback whales will reach carrying capacity before 2026, showing how management actions can support recovery of natural populations.
The 2019 assessment found the resilience of the Region’s coral reef habitats had been substantially reduced by various disturbances. Since then, signs of resilience have emerged, despite mass coral bleaching events in 2020 and 2022. These include the recovery of coral cover at many shallow offshore reefs, driven primarily by fast-growing Acropora. However, inshore reefs in some areas have not shown similar levels of recovery. Loss of local species diversity has been reported over time in the wake of multiple disturbance events at reefs around Lizard Island, and may also have occurred more widely. While the resilience is considered to have improved since 2019, shortening recovery windows are expected to have implications for the ongoing resilience of coral reef habitats and the ability of the reefs to maintain their structure and function. The magnitude of changes in coral cover in the last decade may point to increasing instability in coral cover succession dynamics. (The impact of the 2023-24 summer cyclones and mass bleaching event is not known at time of writing and is not considered in this assessment).
Resilience in seagrass meadows is affected by environmental features, such as good water quality and stable climate, ecological processes, grazing pressures and intrinsic characteristics of the meadows. Seagrass meadows in the northern Region have shown resilience since 2019 despite being affected by heatwaves in 2020 and 2022. However, meadows in the southern region of Fitzroy and Burnett Mary regions remain in poor state and are likely to be less resilient to future disturbances.
Sea cucumbers are sedentary and in high market demand. Their population recovery can be slow, so they can be easily overfished. The most recent stock assessment indicates the biomass of black teatfish has shown some recovery since the fishery was closed in 2001, but it has been slower than expected. Confidence in stock assessments is hampered by uncertainty regarding some biological parameters.
Spawning stock of coral trout has steadily increased since 2012. The latest stock assessment indicates biomass is currently at 60 per cent of unfished biomass, an increase from 2011. Coral trout populations have benefited from local management actions as well as increases in coral cover in some locations. However, resilience of this species is at risk due to ongoing cumulative disturbances that cause coral loss and habitat degradation.
Despite the Region’s loggerhead turtle population showing initial recovery in response to the local management actions, the population is facing a suite of continuing and increasing threats. Climate change impacts and interactions with marine debris are concerning. Recruitment of young turtles to foraging grounds has declined by half over recent decades. This will have negative consequences for the population’s resilience into the future.
Dugong populations continue to show an overall long-term decline. More significant declines have been detected in the southern Region. The 2022 floods in the Burnett Mary region resulted in significant seagrass losses likely to directly affect dugong populations. Resilience of dugongs continues to be influenced by interactions between local impacts and climate change, primarily those that affect seagrass meadows.
Humpback whales have demonstrated resilience to past overharvesting, fully recovering to their pre-whaling population size. Currently, the estimated rapid recovery rate suggests humpback whales will likely reach carrying capacity in the Region before 2026. Resilience of this species will now depend on ongoing impacts of climate change, particularly on their food source outside the Region.