At a glance
Australia’s marine environment is experiencing pressures from a wide range of sources that affect its habitats, communities, species and ecosystem functioning to varying degrees. With many pressures affecting the marine environment and its inhabitants at any one time, it can be difficult to attribute observed impacts to individual pressures. It is particularly difficult to understand or predict how individual pressures will interact and what the cumulative impacts will be.
The overarching pressure that is currently affecting the marine environment—and will continue to affect it even with reduction of greenhouse gas emissions—is climate change. Anthropogenically driven ocean warming, superimposed on natural climate variations, and ocean acidification pose risks to Australia’s coral reef ecosystems, and giant kelp and other habitats, including deep-ocean communities. Sea surface temperatures are continuing to increase nationally, with waters in the South-east and South-west marine regions increasing at a rate of more than 0.4 °C per decade. There is already evidence that, as waters have warmed, some species have shifted their distributions towards the poles, altering marine ecosystems. Changes to nutrient supply and dissolved oxygen are also projected to occur because of climate change; however, observations are insufficient at present to identify whether changes are occurring.
Extraction of resources—such as seafood, and oil and gas—from the marine environment is highly variable in its distribution and impacts. Many pressures associated with the extraction of resources are highly localised, and the likelihood of recovery of affected habitats, communities and species is high once the pressure is removed. Other pressures are more widespread or more persistent, or both, leaving little likelihood of recovery in the short to medium, and even long, term.
Overall, the footprint of pressures within Australian waters associated with commercial fishing has decreased in the past decade. Pressures associated with recreational fishing are generally stable, although, for some species, recreational catches now exceed commercial catches and are increasing. Pressures associated with the oil and gas industries, marine mining and dumping of waste tend to be localised, and are either stable, declining or increasing, but with the prospect that they may decline because of recent legislation.
Use of the marine environment by commercial and recreational vessels continues to increase. The risks associated with such activities that are not currently actively managed (e.g. anchor scour, ship strike, noise) are also increasing. High, but variable, concentrations of marine debris are found in all marine environments, and it is expected that marine debris will continue to be a ubiquitous problem because of continued growth in plastics production and use. As a result, marine debris has been identified as a key threatening process for marine vertebrate species. There is insufficient understanding of the long-term impacts of chronic noise in the marine environment, or trends in toxins, pesticides and herbicides.
Pressures affecting the marine environment are distributed unevenly, resulting from variable uses of the marine environment on local scales, and from broader spatial and temporal variability in climatic and oceanographic processes.
In general, pressures on the marine environment tend to be greater in inshore environments than in offshore environments because these areas are more readily accessible for human use, closer to coastal infrastructure, influenced by coastal and watershed activities to a greater extent, and exposed to inshore oceanographic processes (which tend to be more energetic than those further offshore) (Evans et al. 2016). The shallower water closer to the coasts also exposes species and habitats in these areas to increased environmental variability. This can result in greater capacity to adapt to change. Habitats or species are at greater risk when they have a lower resistance or adaptability to a certain pressure and/or a lower rate of recovery once the pressure is removed. In deeper areas of the ocean, recovery rates may be so slow that it is impossible to distinguish between recovery taking decades or more and a failure to recover within most management timeframes (Williams et al. 2010b).
Because there are many pressures affecting the marine environment and its inhabitants at any one time, it can be difficult to attribute observed impacts to individual pressures. It is particularly difficult to understand or predict how individual pressures will interact and what the cumulative impacts will be.
While recognising that many pressures that manifest in coastal regions influence the marine environment, pressures associated with the land–marine interface or that predominate in the coastal environment (e.g. coastal development, coastal waterway sedimentation and pollution) are not covered in this report. These are covered extensively in the Coasts report. In particular, readers should refer to the Coasts report for detail on pressures associated with pollution in estuary and embayment regions, pollution associated with land-sourced input of nutrients, aquaculture, port developments and tourism.
Of the pressures assessed in 2016, those associated with climate change are having the highest impacts on the marine environment, with the condition of physical (e.g. ocean temperature, currents and eddies) and chemical (e.g. ocean acidification, nutrients) features of the environment assessed as either deteriorating or uncertain. Pressures associated with oil and gas have decreased in the past 5 years, and most pressures associated with resource extraction and use are considered to have low impact, with either stable or unclear trends. Pressures associated with marine debris continue to be high, and related conditions for the marine environment continue to deteriorate.