OCEANS, ESTUARIES AND PROGRESS

Australia's oceans are diverse, ranging from tropical seas, through temperate to polar waters, and from shallow coastal waters to ocean trenches that can be six kilometres deep. This diversity is reflected in the variety of marine life in Australian waters, including more than 4,000 species of fish, 45 species of whales, dolphins and porpoises, and many species of seabirds. Nineteen of the world's 24 albatross species appear in Australian waters (Zann 1995).

Many Australians like to live on or near the coast and use it for recreation, such as swimming, boating and fishing, as well as economic activity. The economic benefits associated with marine and coastal areas include shipping, tourism, fisheries and offshore oil and gas industries.

Adverse changes in the condition of Australia's oceans and coastal areas affect the size and diversity of marine life. Although changes to marine environments can be the result of many factors, human activities play a substantial role in altering ocean ecosystems. Overfishing and practices such as trawling can deplete natural fish stocks and destroy fragile habitats, degrading the overall condition of marine ecosystems.

Coastal population increases can also degrade marine habitats by increasing the volume of sewage, stormwater, chemical and nutrient run-off that enter river systems and oceans. In turn, human induced changes to marine environments can affect human activities that rely upon healthy ocean environments, such as fishing and tourism.

Many of the ways in which we use our oceans, beaches and estuaries affect the quality of ocean water and the diversity of life within it. An ideal indicator might consider a measure of the biodiversity within them.

As there is no comprehensive and nationally consistent system for measuring the condition of Australia's ocean and coastal ecosystems, this commentary relies upon supplementary measures to provide some indication of whether the condition of Australia's marine ecosystems is getting better. The supplementary measures in this section include the number of Australian fish stocks classified as overfished and/or subject to overfishing, and the marine area protected by the Commonwealth Government. Information on the extent of coastal development, marine oil spills, and bycatch and illegal fishing is also included.

For a full list of definitions, please see the Oceans and estuaries glossary.