Population

Australia’s growing population inevitably places increasing demands on the marine environment by increasing demand for marine resources and increasing production of waste products that find their way into the marine environment.

Traditional Owners have expressed concern about the increasing development footprint with population growth (Dawul Wuru Aboriginal Corporation & Yirrganydji People 2014). While human threats cause a loss of dollars to the Australian economy, they are not often considered with respect to cultural and social impacts on Traditional Owners. When rubbish continuously washes up on shores and fishing becomes unsustainable, it causes concern for Traditional Owners, because of disruptions and breakdowns in the health of ocean ecosystems, livelihoods and culture. This concern is amplified when Traditional Owners are not involved in correctional actions, identifying what interventions are working and determining how to best focus efforts to help restore the vision of a flourishing ocean.

Assessment Pressures on the environment associated with population growth

2021

Adequate confidence

Indigenous assessment

Pressures associated with human population have high impact on Australia’s marine environment. The trend for recreational fishing pressure and dumped wastes is stable, but the state of marine debris and plastics continues to worsen, and the pressure this creates on the Australian marine environment continues to increase. The Traditional Owner assessment for recreational fishing agreed that it had a high impact on sea Country, and concluded that the pressure was increasing rather than stable. Note that the spatial scale of Indigenous and western science assessments may be different. Related to United Nations Sustainable Development Goal targets 8.4, 14.1, 14.4

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Assessment Recreational fishing

2021

Limited confidence

2016

2011

Pressure from recreational fishing is substantial for specific species. Trends are variable across marine regions (Lynch et al. 2021b). The Indigenous assessment regionally was high impact, with a deteriorating trend.

Assessment Marine pollution (other than plastics and debris)

2021

Adequate confidence

2016

Sediments and contaminant inputs continue to cause substantial impacts in marine ecosystems, most notably as key contributors to the continual deterioration of the integrity of reef ecosystems (Gagnon 2021). The Indigenous assessment regionally was low impact, with an unclear trend.

Assessment Dumped wastes

2021

Adequate confidence

2016

Dumping of dredged material is considered to be low impact relative to other pollution pressures, but potential cumulative and synergistic effects are a critical research gap (Trebilco 2021a).

Assessment Marine plastics and debris

2021

Adequate confidence

2016

2011

Increasing litter losses into the marine environment are expected to continue, with a corresponding increase in impacts on marine fauna (Hardesty et al. 2021a).

Recreational fishing

In Australia, participation in recreational fishing is high compared with global levels (Arlinghaus et al. 2015, Hyder et al. 2018, Lynch et al. 2021b).

Recreational fisheries are often characterised by a concentration of effort close to large urban population centres (West et al. 2015, Ryan et al. 2019a). Spatially stable hotspots of effort are also associated with habitat features and access points (Lynch 2006, Lynch 2014, Wood et al. 2016, Flynn et al. 2018). In the past 30 years, improved infrastructure, shifting demographics, increased tourism and improvements in technologies have also led to a growth in recreational fishing in regional and offshore areas (Griffiths & Fay 2015, Voyer et al. 2017).

There has been a declining trend in fishing participation and effort in some jurisdictions in recent years (West et al. 2015, Lyle et al. 2019, Ryan et al. 2019a, Winstanley 2019), and stable or increasing trends in others (Giri & Hall 2015); trends vary by state. It is unclear whether the current trends in participation will continue.

Pressures caused by recreational fishing

The intensity of recreational fishing activities can pose a threat to both stocks and marine biodiversity, at least at a local scale (Henry & Lyle 2003, Stuart-Smith et al. 2008, van Putten et al. 2017, Edgar et al. 2018a, Little et al. 2019). For some species, the proportion of the catch taken by recreational fishers can be large, at times rivalling or exceeding the harvest from commercial fisheries. For example, recreational catch of southern sand flathead (Platycephalus bassensis) in Tasmania in 2017–18 was 50 times the catch of the commercial fishery (Lyle et al. 2019), and the estimated recreational catch of King George whiting (Sillaginodes punctatus) in South Australia in 2013–14 was more than half (58%) of the total harvest (Giri & Hall 2015).

Fishery‐independent survey data have shown recent declines in nearshore harvested species (Edgar et al. 2018a), which suggests that impacts of recreational fishing on shallow-water inshore environments should be of concern (Little et al. 2019). It is important to note that, even if participation has remained stable or declined, fishing power has substantially increased as a result of continual improvements in technologies (Lynch et al. 2021b).

Although it is an important pressure in the marine environment, recreational fishing can also have positive socio-economic roles, creating significant economic activity, providing nutrition, and playing an important social and leisure role for coastal communities (Pascoe et al. 2014, Griffiths et al. 2017, Cooke et al. 2018b). It may also positively influence the sense of place or stewardship for individuals or communities.

Assessment of the impacts and management of recreational fishing

Recreational fisheries, although often licensed, are open access with no cap on participation. Except for a small amount of no-take marine reserve and fisheries closures, most coastal and marine waters are available to fishers (Ochwada-Doyle et al. 2014, Kenyon et al. 2017).

Most states undertake semi-regular statewide surveys to determine the extent of effort and associated catches. The frequency at which surveys occur, however, is variable between states, and the last national recreational catch survey was in 2001 (Henry & Lyle 2003). Recreational data are included in some jurisdictional species-level stock assessments across Australia (e.g. rock lobster in Tasmania and Western Australia), and efforts are being made across jurisdictions to further incorporate recreational data into assessments and harvest strategies (see Commercial fishing). Where quality data are available, they are also accounted for in Commonwealth fisheries assessments; a recent example is the inclusion of a recreational allocation in the Southern Bluefin Tuna fishery (5% of Australia’s total allowable catch). This allocation was set based on a national recreational fishing survey that aimed to quantify the recreational harvest (Tracey et al. 2020). 

A lack of coordination in data collection between jurisdictions makes management difficult, particularly if species migrate (Lynch et al. 2019). National coordination is needed to align state surveys and remove technical barriers to comparison. Additionally, identification of key species and targeted survey methods to assess them across their distributional ranges (including across jurisdictional boundaries) with a reasonable level of statistical certainty are likely to be important aspects of recreational fisheries assessment.

Marine plastics and debris

Marine debris is recognised as a globally important stressor in the marine environment. Reports of impacts on marine biodiversity have increased during the past 4 decades (Gall & Thompson 2015, Claro et al. 2019). High (but variable) concentrations of marine debris are found in both coastal and marine environments (Hardesty et al. 2017, Hardesty et al. 2021a). Based on research in the Great Australian Bight, it is estimated that there are 25 times (or more) more microplastics on the seabed floor than floating on the ocean’s surface, with more than 14 million tonnes of debris across the ocean floor (Barrett et al. 2020).

Australia, as an island nation, receives some inputs from neighbouring countries, particularly in the Gulf of Carpentaria region. Generally, however, most of the pollution on our shores and in our nearby environment is domestic in origin (Hardesty et al. 2016) and is trapped in the coastal environment (Olivelli et al. 2020). Three-quarters or more of marine debris is estimated to come from land-based sources, and plastics production and use continue to grow. In 2016, an estimated 19–23 million tonnes (11% of plastic waste) entered the ocean (Borrelle et al. 2020), increasing from the 6–12 million tonnes of plastic waste estimated to enter the ocean in 2010 (Jambeck et al. 2015).

Litter losses into the marine environment are expected to continue to increase, with a corresponding increase in impacts on marine fauna, and associated socio-economic, environmental, navigation and hazard impacts (Wilcox et al. 2020).

Pressures caused by marine debris and plastics

In Australia, marine debris has been identified as a key threatening process for threatened and endangered vertebrate fauna in an Australian Government threat abatement plan (DEE 2018). Marine litter also has socio-economic impacts, acts as a transporter of invasive species and can be a navigation hazard. There are increasing concerns over the human health and food security risks arising from marine plastics in seafood (Rochman et al. 2015).

Marine fauna as small as plankton and as large as cetaceans are known to interact with marine debris (Vegter et al. 2014); entanglement, ingestion and chemical contamination are the 3 main types of interaction (Wilcox et al. 2016). Corals, lugworms, molluscs, commercial fish (Rochman et al. 2015), seabirds (e.g. Acampora et al. 2014, Wilcox et al. 2015, Roman et al. 2019), sea turtles (e.g. Schuyler et al. 2012, Wilcox et al. 2013, Schuyler et al. 2014, Schuyler et al. 2016), pinnipeds (e.g. Lawson et al. 2015), whales (Walker & Coe 1990, Laist 1997) and dolphins (Di Beneditto & Ramos 2014) are all reported to be impacted by marine debris; significant quantities of plastics have been reported in the digestive tracts of several species of marine vertebrates in Australian and surrounding waters (e.g. Carey 2011, Acampora et al. 2014, Lavers et al. 2014, Roman et al. 2020).

Marine mammals may experience more dire consequences resulting from entanglement than from ingestion, although data are lacking for marine mammals in Australian waters. In northern Australian coastal areas, crocodiles, dugong, sawfish, turtles and crabs have been reported to be ensnared in derelict fishing nets, which can result in death (Gunn et al. 2010). Recent studies have found plastics in multiple commercially important fished species in Australian waters; microplastics have been reported in fish, bivalve molluscs (Jahan et al. 2019, Dawson et al. 2021) and shrimp (Nan et al. 2020).

Assessing changes in marine debris and plastics

A circumnavigation of Australia’s marine estate in 2011–13 evaluated floating plastics and found concentrations as high as 40,000–80,000 pieces per square kilometre (Queensland), but more commonly 1,000–40,000 pieces per square kilometre (see Reisser et al. 2013). This national survey highlighted the variability of floating plastics in the marine environment and the lack of ongoing, national monitoring of this kind. Establishing a national baseline and monitoring for marine plastics (and microplastics, in particular) remain key needs. Several researchers around Australia (e.g. Australian Institute of Marine Science, University of Western Australia) are conducting surface tows for microplastics, with an increasing focus on microfibre contamination (Jensen et al. 2019).

Recent work in the Great Australian Bight found high levels of microplastics from deep-sea sediment cores (up to 3,000 metres deep; Barrett et al. 2020), further demonstrating the ubiquity of these materials in Australian waters. It is estimated that around two-thirds of coastal debris in Australia is plastic, based on a robust, continental-wide survey that showed an average density of 0.15 items per square metre (Hardesty et al. 2016).

Uncertainties persist around the entanglement and ingestion risk to cetaceans in Australian waters; the population-level impacts of marine litter on marine fauna, including commercially and recreationally caught food fish, sea turtles, marine mammals and seabirds; the frequency and potential economic impact of transport of invasive species via hitchhiking on marine debris; the changes (or trends) in litter distribution, origins and losses into the environment (KA Willis, CSIRO Oceans and Atmosphere, pers. comm., 2021); the cost of marine debris to fisheries and small businesses in Australia; and the potential links between ingested plastics and human health from seafood.

New legislation has passed in some jurisdictions (state and local) around Australia, and public awareness and response are changing. With the new waste export ban and post-pandemic recovery on the horizon, increasing focus on domestic waste management and on a plastics circular economy is likely (Hardesty et al. 2021a).

It will be important to measure the impacts of the activities, campaigns and legislation on reducing waste mismanagement, and the associated losses of waste into the coastal and marine environments (Willis et al. 2021). Understanding whether plastic bag bans, banning of microbeads in personal care products and awareness-raising campaigns are successful in reducing impacts on Australia’s coastal and marine estate will be imperative. Container deposit schemes have already proven to be effective in reducing debris, as have waste abatement campaigns and waste infrastructure (Schuyler et al. 2018, Willis et al. 2018, Willis et al. 2019).

Other marine pollution

In addition to marine plastics and debris, and anthropogenic noise, forms of marine pollution that are of national concern include land-based nutrients, pesticides, sediment inputs and hydrocarbons (Kroon et al. 2020, Gagnon 2021, Trebilco 2021a).

Pressures caused by marine pollution

These types of pollution have a wide variety of impacts on marine plants and animals, ranging from reduced photosynthetic activity (plants) to endocrine disruption, reduced immunity or modified behaviour (animals).

The 2 main sources of sediment input in the marine environment are land-based run-off and dredging activity associated with the development and maintenance of ports. Input of sediment and other pollutants (particularly excess nutrients, as well as contaminants and toxins) from river plumes (terrestrial run-off) is an important pressure, particularly in inshore areas (see the Coasts chapter). The influence of such terrestrial inputs extends across the entire continental shelf in some areas (e.g. the north-east; Waterhouse et al. 2017, GBRMPA 2019). Coal particles are another land-based pollution pressure that may be important in some areas, but impacts are not well understood (Kroon et al. 2020).

Dredging itself is an important pressure, with both direct impacts from physical disturbance in dredged areas and downstream impacts from the sediment plumes it creates (see the Coasts chapter). The main pressure associated with dredging in the marine environment arises from the disposal of dredged material on the sea floor.

The areas selected as disposal sites and the nature of dredged material disposed of at sea are regulated to minimise the risk of marine organisms being exposed to toxic materials (Ports Australia 2015). Pressures arising from this practice can include direct burial of organisms and less direct impacts arising from resuspension of sediments placed on the sea floor, which reduces water quality (see Water clarity (turbidity, transparency and colour)). Although the footprint of disposal sites is relatively small on the scale of Australia’s continental shelf, the area affected by resuspended material is potentially larger and less well known (McCook et al. 2015, Mills & Kemps 2016, WAMSI 2019).

Assessing changes in marine pollution

At-sea disposal of dredge material has decreased during the past 5 years (2016–21) (GBRMPA 2019, Jones & Twomey 2019, Trebilco 2021a). There has been a continued trend of increased willingness by port operators to dispose of dredged material on land for later re-use. Dumping of dredged material is therefore considered to be low impact relative to other pollution pressures, but potential cumulative and synergistic effects are a critical research gap (WAMSI 2019).

Improvements in land management practices have reduced the input of land-based sediments and contaminant inputs over inshore reefs, which are still experiencing a high impact from land-based runoff (e.g. DES 2019) However, these improvements have not yet been implemented at a scale or timeframe that results in a measurable difference to the health of marine ecosystems. It is likely that there are significant timelags between changed land management practices and measurable improvements in marine ecosystem processes (GBRMPA 2019, Gagnon 2021).

The use of low-sulfur fuel oils (LSFOs) by all vessels is now a mandatory requirement introduced by the International Maritime Organization from January 2020. Although sulfur content has been reduced to 0.5% (mass per mass) (IMO 2019), the physicochemical characteristics of LSFOs are highly variable, and little is known of their fate and behaviour once in the environment, should an accidental discharge occur. Australia has not yet experienced major oil spills involving LSFOs.

Tourism

Tourism in Australia’s marine and coastal environments is extremely economically valuable: tourism constitutes one of the largest individual subsectors, by value, of Australia’s marine industry (AIMS 2021a) (see case study: The blue economy). (see the Coasts chapter)