At a glance
Marine biodiversity overall is in good condition, but nationally there are a number of areas on the coast, continental shelf and upper slope where the condition of some elements of biodiversity is very poor, as a result of the effects of specific human activities. Condition remains poor to very poor for a number of iconic species that have failed to recover from earlier impacts of excessive hunting and fishing, and some species continue to decline. These include Australian sea lions, which are unique to temperate southern Australian waters and are showing no substantial signs of population recovery from the hunting of previous centuries; and migratory wading birds, which appear to be continuing to decline across many of their Australian habitats. Southern bluefin tuna, formerly a major predator of our regional seas, has been fished to the edge of population survival but is now listed as conservation dependent under the Environment Protection and Biodiversity Conservation Act 1999; its global catch has been reduced, and a management procedure has been proposed that is intended to rebuild the population.
In addition to national-scale biodiversity problems, there are many more habitat and species issues in smaller local areas. These judgements are based on a generally low level of certainty, with most of the available knowledge linked to fished species and threatened species. A much more detailed national assessment of marine biodiversity is required to properly clarify the nature, extent and significance of the condition of our marine biodiversity.
The overall health of our marine ecosystems is good, but this finding is influenced by the good condition of the offshore waters and the remote coastlines of regions where pressures are lowest. In inshore waters near the coast of the south-west, east and south-east regions, and near urban areas and industrial developments, the ecosystems are in poor health. Algal blooms occur regularly; natural levels of freshwater, sediment and nutrient inputs have been heavily altered; and worrying levels of pesticides are found in waters near areas of intensive agriculture. The ecosystem health of some nearshore marine waters and many estuaries is poor, particularly across the temperate areas and in many parts of the south-east region. In this report, the south-east region is assessed to be in the worst condition: most places are good, but the worst 10% of the region is poor—existing values are significantly impacted, and serious further degradation is expected within 50 years.
Australia's marine environment encompasses the structures of the seabed, ocean and shoreline systems, marine and estuarine waters, and their species and biological structure and function, all of which interact in a complex and interdependent web. Biodiversity and ecological health is assessed and reported here for:
- marine biodiversity
- quality of marine habitats for marine species
- populations of the main types of marine species
- ecological processes that support biodiversity and habitats
- ecosystem health
- quality of the physical and chemical processes that maintain the health of marine ecosystems
- extent of diseases, algal blooms, pests and introduced species.
For this SoE report, the condition and trends for the main aspects of marine biodiversity and ecosystem health have been assessed within each of the major Australian marine regions (Figure 6.9). These five regions include the Australian Government’s marine planning regions, the extended continental shelf, the offshore islands and territories (other than the subantarctic islands), and the state and internal waters, up to high tide level at the shoreline. The assessment of conditions reported here must be interpreted with caution, because studies and data directly relevant to the Australian marine environment are limited. The assessments reported here are derived from available data and information, and from the judgement of a limited number of experts who participated in the national marine condition assessment workshops that contributed to the analyses presented here.