Australia's Coastal Pollution: Understanding The Main Causes

Australia's oceans are among the most diverse in the world, with 33,000 marine species identified and estimates of up to 500,000 species in total. The country's coasts and oceans are under threat from plastic pollution, climate change, unsustainable fishing practices, and acid sulfate soils. While plastic pollution in Australia has decreased by 29% since 2013, plastic waste remains an issue, with each square kilometre of sea surface water contaminated by around 4,000 pieces of plastic. This pollution poses risks to marine life, ecosystems, and human health.

Plastic pollution

In Australia, plastic pollution has decreased by 29% since 2013, according to a study by the national science agency CSIRO. This decrease is attributed to improved waste reduction strategies and local government efforts to prevent and clean up pollution. However, plastic pollution remains a significant issue, with plastics representing the majority of human-made debris in Australian oceans.

The breakdown of larger objects, such as packaging and fishing items, results in small fragments called "microplastics," which are prevalent in Australian waters. These microplastics have a median length of 2.8 mm and can be ingested by marine organisms, causing internal injuries or death. High plastic concentrations have been observed near populated areas, such as Sydney and Brisbane, indicating that plastics along the east coast are associated with domestic inputs.

The impact of plastic pollution on marine life is significant. It affects at least 267 marine species, including endangered ones. Sea turtles, for example, often mistake plastic bags for jellyfish, their natural prey, leading to obstruction of the oesophagus and death. Abandoned fishing gear and discarded six-pack rings also entangle and strangle seals, whales, turtles, and other animals.

Plastics in the ocean absorb hazardous chemicals over time, and these toxins are eventually ingested by marine life, potentially entering the human food chain. The accumulation of plastic waste in landfills and the environment contributes to greenhouse gas emissions, with Australia's plastic consumption equivalent to the emissions of 5.7 million cars annually.

Community involvement in clean-up activities and surveillance programs has been effective in reducing plastic pollution in Australia. Bans on single-use plastics and initiatives to reduce plastic packaging in supermarkets have also contributed to positive change. However, there is still a long way to go in addressing the global crisis of plastic pollution.

Climate change

The effects of climate change on Australia's coastal ecosystems are evident in the degradation of its coral reefs, particularly the iconic Great Barrier Reef. Ocean warming and acidification, driven by climate change, have led to coral bleaching and the destruction of these diverse ecosystems. The loss of coral reefs has far-reaching consequences for marine life, as they provide essential habitats and contribute to the overall health of coastal environments.

Additionally, climate change has influenced changes in precipitation patterns, resulting in more frequent and intense rainfall in certain regions. While rainfall can help dilute pollutants and facilitate their breakdown, it can also mobilize and transport pollutants into coastal areas through runoff and stormwater discharge. This runoff often carries pollutants such as fertilizers, pesticides, and heavy metals from agricultural and urban areas, ultimately leading to the contamination of coastal waters.

The impact of climate change on Australia's coastal pollution is further exacerbated by the presence of coastal acid sulfate soils. When exposed to oxygen through drainage or excavation, these soils produce large quantities of sulfuric acid. Rainfall, especially after prolonged dry periods, mobilizes this acid, along with other toxins, into surrounding waterways, significantly degrading water quality.

To address the coastal pollution caused by climate change, Australia has implemented various measures. The country has shown progress in reducing plastic pollution, with a 29% decrease in coastal plastic pollution since 2013, achieved through improved waste management and cleanup initiatives. Additionally, organizations like the World Wide Fund for Nature (WWF) have been advocating for the protection of marine areas and promoting sustainable practices to mitigate the impacts of climate change on Australia's coasts.

Poor water quality

One of the main causes of poor water quality in Australia is plastic pollution. Plastic pollution on Australia's coasts has decreased by 29% since 2013, according to a study by Australia's national science agency, CSIRO. This decrease is attributed to improved waste reduction strategies and local government initiatives. However, plastic pollution remains a significant issue, with each square kilometre of Australian sea surface water contaminated by around 4,000 pieces of tiny plastics. These microplastics, smaller than 5mm, are loaded with toxins that can negatively affect marine life and potentially human health.

Plastic waste enters the ocean through various pathways, including rivers, wind, tides, rainwater, storm drains, sewage disposal, and direct disposal from boats and offshore installations. Once in the ocean, plastics break down into smaller pieces due to sunlight and heat, becoming increasingly toxic by absorbing oily pollutants. These toxins can be ingested by marine life, leading to biomagnification in the food chain, and potentially impacting human consumption.

Another factor contributing to poor water quality in Australia is the exposure of coastal acid sulfate soils to oxygen through drainage or excavation. This process releases large quantities of sulfuric acid, which, along with other liberated toxins like heavy metals, flows into surrounding waterways, decreasing water quality.

The protection of Australia's marine environments is imperative, given that oceans play a fundamental role in sustaining everyday life. Organisations like WWF-Australia and CSIRO are actively working towards better protections for oceans and the reduction of plastic pollution.

Coastal acid sulfate soils

CASS is the term usually given to soils or sand that contain iron sulfides (predominantly the mineral pyrite) and/or their oxidation products. In their undisturbed state below the water table, CASS is relatively harmless. However, when exposed to oxygen through drainage, excavation, or dewatering activities, the sulfides react with oxygen to form sulfuric acid.

The release of sulfuric acid from the soil can, in turn, release iron, aluminium, and other heavy metals and metalloids (particularly arsenic) within the soil. Once mobilized in this way, the acid and metals can create a variety of adverse impacts, including killing vegetation, seeping into and acidifying groundwater and surface water bodies, killing fish and other aquatic organisms, and degrading concrete and steel structures.

The impacts of acid sulfate soil leachate can persist over long periods, and in some areas of Australia, CASS that drained a century ago are still releasing acid. Disturbing potential acid sulfate soils can have a destructive effect on plant and fish life and aquatic ecosystems.

Unsustainable fishing practices

Australia's oceans are among the most diverse in the world, with around 33,000 marine species identified and estimates placing the figure as high as 500,000. However, unsustainable fishing practices are pushing vulnerable wildlife to the brink.

One such unsustainable fishing practice is bottom trawling, which is when a net is dragged along the seafloor to catch fish. Bottom trawling is particularly destructive because it can damage seafloor ecosystems and habitats, such as coral reefs and mangroves, that are essential for marine life and act as carbon sinks to mitigate the effects of climate change. China, Vietnam, Indonesia, India, and Morocco are the top five countries in terms of the average catch from bottom trawling, with China alone accounting for 15% of the total bottom-trawled catch. While bottom trawling is declining or remaining constant in most parts of the world, it is expanding rapidly in Asia.

Another unsustainable fishing practice is the use of fish aggregating devices (FADs) in purse seine fisheries. FADs are floating objects, such as buoys or rafts, that are used to attract and capture fish. They are often used in the tuna industry and can have a negative impact on marine life by increasing the number of non-target species, such as dolphins, turtles, and seabirds, that are accidentally caught in fishing nets. This is known as bycatch. While some companies have committed to ending the use of FADs, sustainable alternatives such as pole and line fishing, do exist.

In addition to these practices, unsustainable fishing at a commercial scale can also be attributed to advanced fishing techniques driven by global demand. These techniques allow for the location and harvesting of fish at a rate faster than their reproduction, which strips away biodiversity and threatens the livelihoods of those who rely on these waters for food and income.

To address these issues, organizations like Greenpeace Australia Pacific and WWF-Australia are advocating for sustainable fishing practices and the protection of marine environments. For example, WWF-Australia purchased and retired two commercial fishing licenses in 2016 to help create a safe haven for threatened marine wildlife in the Great Barrier Reef. Additionally, Greenpeace Australia Pacific's Canned Tuna Guide campaign in 2009 led to all major Australian canned tuna brands becoming FAD-free by 2017.

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