Coasts and oceans: Pressures on Australia's coasts and oceans

Independent report to the Australian Government Minister for the Environment and Heritage
Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis
(2006 Australian State of the Environment Committee), 2006

6.2 Pressures on Australia’s coasts and oceans

Urban development

Australia’s coasts are under increasing pressure as existing towns and cities spread to accommodate Australia’s growing population (see ‘Human settlements’). Australia-wide, most of the coastal development —some 77 per cent of it—has been there since 1980. Moreover, the rate of urbanisation has slowed since 1989. If these trends continue, 42.3 per cent of the Nowra to Noosa coastline will be urbanised by the year 2050, with the resulting loss of much of Australia’s temperate and tropical coastal systems and stress on existing infrastructure. For the Australian coastline as a whole, the proportion will be 9.2 per cent. In addition, the Tasmanian coastline has been under increasing pressure during the reporting period (Figure 25).

Although 9.2 per cent may seem like a small proportion of the massive Australian coastline, urban development along the coastal strip is one of the main pressures on Australia’s coastal environment. Replacing ecological communities with urban infrastructure threatens much of the temperate coast and tropical systems, especially near existing centres of population. All existing threats and pressures are intensified; this is in addition to the complete loss of habitat in the newly urbanised areas and the loss of many significant coastal Indigenous heritage places. The heritage landscapes of small coastal towns are similarly threatened by population increases and by urban development that is often unsympathetic or poorly planned.

The impact of continued urban expansion on coastal water quality could be a serious issue, particularly when combined with nutrients, chemicals and sediments  entering the sea from rivers draining agricultural catchments. The effect has been the creation of localised and increasing ‘pollution halos’ around these areas, such as the contamination in Port Phillip (Victoria) and the toxic sediments at the bottom of Sydney Harbour (New South Wales). Dioxin levels in some fish and seafood have been high enough to suspend all commercial fishing in Port Jackson and its tributaries (NSW Food Authority 2006). Further areas are not expected to develop (Turner et al 2004) because much of the Australian coast is now subject to significantly better management practices than in even the 1970s and 1980s, but improvements are not keeping pace with pressures. With the increased urban spread, a realistic fear is that pollution halos will begin to link up and form bodies of polluted water that are not easily dispersed, which would affect many types of marine life.

Halting and reversing the decline in coastal water quality is a long, slow process. For example, the Swan River Trust began its efforts to improve water quality in the Swan–Canning river system in 1994 with a study of the problems caused by increased algal blooms.

A few local councils, such as Noosa in Queensland and Surf Coast Shire in Victoria, have attempted to limit growth to a rate at which they can provide essential infrastructure, such as water supply. It is local government, after all, that bears most of the burden of managing the impacts, and some outside the capital cities have found that they do not have the financial and other resources to adequately manage the cumulative adverse impacts on the natural environment (Wild River 2006). On the other hand, many councils find it hard to justify forgoing the perceived benefits of the ‘sea change’ phenomenon and have actively supported surges in migration and tourism.


Intensive agriculture is a pressure on Australia’s coasts and oceans, particularly estuaries and nearshore environments. Modelling predictions estimate that each year almost 19 000 tonnes of total phosphorus and 141 000 tonnes of total nitrogen are discharged to rivers flowing to the coast (NLWRA 2001c). The highest nutrient loads  are expected to be in the Far North of Australia, northern Queensland, Moreton Bay and coastal New South Wales.

Large quantities of total nitrogen have been discharged into rivers within ten kilometres of the coast since 1998 (the year when reporting nutrient emissions through the National Pollutant Inventory began). Total phosphorus discharges have also been significant. The number of facilities reporting discharges to water within ten kilometres of the coasts increased from 400 in 1998–99 to 1 142 in 2003–04 (Table 12); most of these are sewerage treatment plants and there are some intensive agricultural operations.These discharges are likely to be having at least a localised effect on fish, marine life, ecosystems and biodiversity, but despite this increase there are no national-level data on the impacts of these discharges.

Table 12: Number of coastal-based facilities reporting emissions to the NPI
Number of facilities 1998–99 1999–2000 2000–01 2001–02 2002–03 2003–04
0–10 km from coast 400 686 826 956 1 090 1 142
10–50 km from coast 297 551 691 906 1 047 1 123
Total number coastal NPI facilities 707 1 260 1 550 2 039 2 173 2 297

Note: NPI – National Pollutant Inventory

Source: NPI website >, accessed May 2005

Many eastern coastal lakes are suffering from land use change and forest clearing in their catchments, suburban development, alteration of freshwater inflows, storm and wastewater discharges, overfishing and resource development of various kinds. All are showing some kind of human impact (DEH 2006d, Harris 2006).


Fishing is a continuing pressure on marine ecosystems. While Australia’s fisheries are limited compared to those of some other countries, they are also an important source of recreation, livelihood and wealth in many coastal areas of Australia. The pressure of overfishing generally and the consequent depletion of stocks and increasing regulation will have an accelerating effect on traditional Indigenous subsistence activity  in some areas.

Australia’s commercial fisheries are amongst the most diverse in the world, exploiting more than 300 species—including fish, cephalopods (such as octopus and squid) and shellfish. In 2003–04, Australia’s commercial fisheries  (including aquaculture) produced about 267 000 tonnes of seafood valued at about $2.2 billion (ABARE 2005b). In terms of tonnage, 70 per cent of Australia’s fish are caught in state-managed waters. Although some states and territories assess the status of their fisheries, these assessment processes are different from those used for Commonwealth-managed fisheries, and so a meaningful nationwide assessment is difficult, if not impossible.

The data that are available show a decline in Commonwealth-managed fisheries  (Figure 26). Among the 74 species that are Commonwealth-managed, the number of stocks that are overfished has increased in the last 12 years and is now at a record-high level of 17 species. The highly migratory Southern Bluefin Tuna (Thunnus maccoyii) is considered to be overfished, but it has not been listed as vulnerable because this would not necessarily lead to a good conservation outcome (Caton and McLoughlin 2005, TSSC 2005). The strong management regime provided by the Commission for the Conservation of the Southern Bluefin Tuna (CCSBT) is seen to be a better way to go. At least some of the additional 40 species for which status is uncertain are likely to be overfished as the trend to higher numbers of overfished stocks has followed more or better information becoming available on those resources. It is likely that similar trends would be seen across all Australian fisheries, and so these data can be taken as a case study with national implications.

Figure 26: Trends in Commonwealth-managed fish stocks

 Trends in Commonwealth-managed fish stocks

Note: Classification categories used in Fishery Status Reports 2004 differ from those of previous reports. Species previously classified as underfished or fully fished are combined in the figure as not overfished. Overfishing counts for previous years are not available.
Source: Caton and McLoughlin (2005)

Recreational fishing (more information on this topic) 

Recreational fishing also places significant pressure on fish populations, particularly for the onshore and nearshore resources. In the 12 months prior to 2000, recreational fishers were estimated to catch approximately 136 million aquatic animals (Henry and Lyle 2003). While many recreational fisheries are managed through size and bag limits for individual fishers, this often does not limit the total catch in the fishery or adequately link the catch to a level that can be sustained by the fish population.

Illegal fishing (more information on this topic) 

Illegal fishing places further pressure on some fish species—Patagonian Toothfish (Dissostichus eleginoides) in the Southern Ocean and shark (for fins) in northern Australian waters being the worst affected. The number of vessels apprehended for illegally fishing in Australian waters more than trebled (from 60 to 210) between 1999 and 2005 (Table 13). This gives some indication of the policing effort required to protect Australia’s fishing stocks.

Table 13: Apprehensions for illegal fishing
Year 1999 2000 2001 2002 2003 2004 2005
Total/year 60 77 80 111 139 161 210

Source: Data supplied by Australian Fisheries Management Authority 2005

Indirect impacts of ‘wild catch’ fishing

The impact of fishing extends beyond the direct harvesting of fish. In Australia’s oceans, some of the most significant impacts are related to bycatch , which includes the accidental catching of other species, such as marine turtles, birds or non-target species of fish. There is still limited reporting of bycatch. Bycatch of marine turtles is one of the two key marine threatening processes that have been declared under the EPBC Act. In the Northern Prawn Fishery, the introduction of turtle exclusion devices dramatically reduced marine turtle bycatch from a high of 883 turtles in 1999, to only 27 turtles in the year 2003. Bycatch includes ghost fishing, which occurs when lost and discarded fishing gear continues to catch marine species indefinitely. Ghost fishing is also one source of marine debris : coastal surveys of northern Australia over recent years (Kiessling 2003) recorded 2566 abandoned fishing nets.

Other examples of indirect impacts of fishing are the disruption that trawling  causes to ecosystems on the seabed, and the effects on the overall structure of marine ecosystems from removing key prey or predator species . These changes have been observed in the fisheries data that are available. For example, deep-water trawling since the south-east fishery started in 1915 has greatly altered the biodiversity of the continental shelf and deeper water ecosystems, with one result being that the principal target species has changed over time. The mix of other, non-target species has altered substantially as the ecosystems have changed (Klaer 2001).


The Australian aquaculture industry  is small by global standards, contributing less than 0.1 per cent of global production by volume (ABARE 2005b). In Australia, the industry is gaining importance as, in 2003–04, it produced nearly 20 per cent of the tonnage of the wild fishery and nearly 50 per cent of the value. About 99 per cent of the Southern Bluefin Tuna catch is now ‘ranched’. As wild-catch fisheries decline, aquaculture is expected to become an increasingly important feature of the fishing industry and of Australia’s coastal regions.

The industry is expected to continue to grow rapidly (Love and Langenkamp 2003), particularly in sea-cage and other in-water operations that require protected shallow coastal sites  of high water quality. As the competition for these sites intensifies, local, state and national planning and management processes will have to improve, as will monitoring of the pressures and impacts. Environmental risks from aquaculture include nutrient loading  of estuarine systems, exotic diseases  and possibly threats to wild populations through genetic alteration and disease.

Coastal and marine pollution

Shipping, and oil and gas exploration and extraction are sources of marine and coastal pollution in Australia’s oceans. In the Great Barrier Reef World Heritage Area alone, some 6 000 large ships pass through each year and three-quarters of them use the inner route along the land side of the reef, carrying a wide range of cargoes, including bauxite and alumina, manganese, iron ore, coal, sugar, silica sand, general container freight and petroleum products. The main pollutants from boats and shipping include ballast water discharges , marine debris  and oil spills .

Waste from marine vessels is a localised pressure for marine ecosystems. Of the total 13 800 tonnes of waste generated each year in Australian waters, 70 per cent is off-loaded at ports and disposed to landfills. There are requirements for waste disposal by vessels traversing the Great Barrier Reef World Heritage Area as well as for tertiary treatment of sewage on offshore Great Barrier Reef islands.

There is little pollution from offshore extraction activities , which include tanker accidents, oil rig spills and wellhead failures, as well as routine emissions from offshore facilities.

Introduced marine species

Ballast water discharges are of concern because of their potential to transport species from their native habitat to new habitats where they may become invasive. Ballast water from shipping has been responsible for introducing more than 250 species, and possibly as many as 500 species, into Australian waters. Australia has introduced mandatory ballast water management requirements to reduce the risk of the introduction of more unwanted marine species. More than 99 per cent of the approximately 12 500 annual voyages that arrive in Australia comply with these requirements.

The transfer of exotic organisms from the hulls of ships  and boats also remains a threat to Australian waters. Two well-known examples include the Asian Green Mussel (Perna viridis), which almost certainly entered at Cairns on the hull of a vessel, and the Black Striped Mussel (Mytlopsis sallei) in the Northern Territory. The Northern Territory now has a hull inspection protocol in place for vessels entering the marinas, which has detected species of concern, including mussels. Even with inspections, there is always the chance that niche areas, such as the internal waterway systems of vessels, will harbour pests but be missed during inspections (Neil et al 2005).