Grading statements — Populations of species and groups of species
Only a few, if any, species populations have deteriorated as a result of human activities or declining environmental conditions.
Populations of some species (but no species groups) have deteriorated significantly as a result of human activities or declining environmental conditions.
Populations of many species or some species groups have deteriorated significantly as a result of human activities or declining environmental conditions.
Populations of a large number of species have deteriorated significantly.
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
Overall, the condition of species and groups of species remains poor on a Region-wide scale, mainly due to the impacts from ongoing climate change and localised reductions in water quality, and there is potential for compounding pressures. There is significant variation between different species and species groups and, in many cases, data are limited. Most populations of marine turtles and seabirds within the Region have declined, as have dugongs in the southern area of the Region, while humpback whales continue to show strong recovery. Increases in cover of some fast-growing corals have occurred, although species diversity and other aspects of coral condition likely remain affected. The condition of seagrasses has improved across many northern regions, but remains poor in the south.
Although continued warming and accelerating sea-level rise are expected to lead to future changes in the local distribution and condition of mangrove species, no substantial changes in the extent or diversity of mangroves have been observed over the past 5 years.
Seagrasses continue to be affected by increasing sea temperatures and localised decreases in water quality. Recent changes in the proportion of colonising and successional seagrass species in northern regions are indicative of seagrass recovery following past impacts from flooding. Seagrasses in the southern regions of Fitzroy and Burnett Mary are in poor condition, primarily due to the impacts of recent floods, and are vulnerable to future disturbances.
Benthic algal cover in shallow reef areas has been relatively stable over the past 5 years. Significant variation exists across this diverse group. Future ocean warming and acidification may adversely affect coralline algae while providing increased opportunities for turf algae and fleshy macroalgae. Populations of microalgae important for coral symbioses may be shifting to more thermally tolerant variants.
Relatively few acute disturbances have occurred since 2019, facilitating recovery of some fast-growing species. Increases in cover of these species contribute to some improvement in condition of corals overall. Nevertheless, recovery across other species is less certain, and overall coral diversity likely remains affected. Crown-of-thorns starfish and reduced water quality have affected corals in some locations. While widespread mortality or loss of diversity after the 2020 and 2022 mass coral bleaching events was not recorded, corals remain extremely vulnerable to rising ocean temperatures.
Significant variation exists in condition (and trend in condition) of different species within this diverse group. Pressures associated with climate change, habitat loss, fishing and poor water quality are likely to have affected invertebrates across a range of habitats within the Region.
Changes in water temperature and availability of inorganic nitrogen likely impact abundance and diversity of phytoplankton within the Region, which has trophic implications for zooplankton and beyond. Calcifying zooplankton may be affected by increasing acidification, though there is no consistent declining trend in calcifier abundance in the Region. From the limited available data, increases in diversity and abundance of warm-water species are evident across many plankton and microbe groups consistent with expectations under climate change.
Changes in the mean abundance of some bony fishes have been observed since 2019, and over the longer term. Trends vary between species groups and regions, and both increases and declines have been observed. In some cases, the observed changes may reflect natural fluctuations in populations. Climate change, habitat degradation, and targeted extraction are exerting pressure on bony fishes, and having varying effects in different species and functional groups.
Overfishing (including unintentional catch) and climate change-related ocean warming and acidification affect many species of sharks and rays worldwide. In the Region, multiple species are in a reduced state compared to historical population levels. Current management tools may be helping to reduce further impacts. More work is needed to understand the condition (and trend in condition) of individual species.
Despite reported declines in some locations, the lack of systematic population monitoring means the status of sea snakes in the Region remains uncertain. Based on the limited available evidence, the condition of sea snakes in the Region is inferred to be stable.
Declining population trends are reported for most species and distinct genetic populations of marine turtles in the Region. Since 2019, the southern green turtle population and eastern Queensland flatback turtles have shown moderate recovery. The nesting population of hawksbill turtles is in significant decline and could be at risk of loss within the next 10 to 15 years. Key threats include climate change, marine debris, national and international take, terrestrial predation, fisheries bycatch and light pollution.
Estuarine crocodile populations have continued to recover following historical reduction to very low numbers. Since 2019, although statewide surveys and genetic studies have highlighted some vulnerabilities, the overall condition of crocodile populations is thought to have improved, and confidence in this assessment has increased.
Overall, confidence in the condition and (trend in condition) of seabirds has improved since 2019 but remains limited. Although available information on population trends is highly site-specific, probable declines are occurring in some species, while other species’ populations appear static or have probable increases. Key pressures in the Region include climate-related environmental changes and depletion of prey species, as well as nest predation by invasive species at some sites.
The available data are nationwide, and shorebird populations must be inferred for the Region. The condition (and trend in condition) of shorebirds in the Region have been assessed as unchanged since 2019. Migratory and resident shorebird species are subject to local pressures, such as disturbance and habitat decline, while migratory shorebirds are vulnerable to habitat loss outside the Region during their migration.
Populations of whale species within the Region are inferred to be stable. Humpback whales have recovered strongly. Climate change is the greatest threat to whale populations and their food sources outside the Region.
Overall, due to multiple and cumulative threats, populations of some dolphin species within the Region are inferred to have continued deteriorating since 2019.
Dugong populations from the Great Barrier Reef region north of Cape Bedford are considered stable, if not increasing. However, between 2005 and 2022 there is evidence of a long-term decline in dugong populations in the south.