Marine debris is polluting the oceans and may threaten vertebrate organisms in marine ecosystems. Durable plastics pose a significant threat to marine wildlife. The most common and most harmful plastic debris consists of shopping bags, drink bottles, and derelict fishing nets, lines and ropes (known as ghost nets). These articles harm marine animals either by ingestion or physical entrapment, when animals are unable to free themselves from loose ropes and nets. Along remote parts of the northern Australian coastline, concentrations of plastic waste have been recorded as more than 400 kg of debris per kilometre. The environmental threat of plastic debris is exacerbated by its durability. Plastics break down into microplastics, as noted in a previous FDI report; they biodegrade very slowly, remaining in the ocean for long periods of time.
In May 2009, responding to the effects of marine debris, the Australian Government enacted a Threat Abatement Plan (TAP). The TAP was designed to identify possible interventions for addressing the harmful and potentially hazardous marine debris accumulating on the Australian coastline. The comprehensive Plan assigned responsibilities to be shared and sponsored across Federal agencies, State and Local Governments, as well as community organisations in programmes such as: Clean Up Australia Day, the Indigenous Sea Range Partnership and the Carpentaria Ghost Net Programme.
In 2015, an Australian Senate inquiry was tasked to identify, review and report on the effectiveness of the 2009 TAP. The inquiry concluded that the key threats identified in 2009 had not abated and the plan objectives had not been achieved. Clean-up programmes, however, had been effective in reducing the volume of marine debris washed up on beaches. Importantly, there was an improved understanding of the problem of marine debris and its detrimental effects on the marine environment. The knowledge has now been applied through improvements to many relevant issues and incorporated in the 2017 (Draft) Threat Abatement Plan. Notably, the new TAP lists several management objectives and actions including, as fourth in the list of priorities, the requirement to ‘remove existing marine debris’.
The 2017 TAP recognises ghost nets as the major component of marine debris threatening the Australian marine environment. Northern Australia has some of the highest densities of ghost nets in the world; hundreds of tonnes wash ashore annually. The cause and extent of this debris can be best understood in the geographic context of the littoral regions of Indonesia, Timor-Leste and Papua New Guinea, where commercial fishers make extensive use of gill-nets to catch herring and other shoaling fish. In this region, fishing sustains livelihoods and contributes to national economies. For various reasons, fishing nets are often discarded, lost or abandoned, to drift in the Arafura and Timor Seas and, eventually, to wash up on the Australian coastline. These nets can extend for more than several hundred metres in length, making their removal difficult, particularly from isolated locations. Burning on site often constitutes the only method of disposal, if removal to a waste management facility is not a viable alternative.
It is hoped that efforts will focus on improved collection and removal of marine debris from the sea. In this respect, the 2017 TAP has recommended that Australian Government vessels be provided with electronic digital transponders, which could be attached to ghost nets (and any other large debris items) for tracking and later retrieval. While this is a sound concept, it will require considerable support to collect the ghost nets for on-shore disposal or re-cycling. Also needed are devices that skim the water to collect surface, submerged and suspended debris. While there is promising research in Europe and the US, few systems currently exist in Australia, necessitating the development and implementation of suitable technology.
The scientific community is also investigating alternative ways of managing marine debris. The environmental half-life of some plastics is up to 100 years, which means that plastic debris present in the oceans now and discarded in the immediate future, will take many years to biodegrade to a point where it is no longer a threat. Research is being conducted to develop plastics that will quickly degrade and break down when exposed to sunlight and the marine environment, but it will be some years before new plastics will be in common use.
In late 2017, FDI reported on Australia’s leadership at the United Nations Environment Assembly, where it successfully promoted awareness of the issue of marine litter and micro-plastic pollution. This saw the UN resolving to convene an expert group charged with assisting developing countries to participate in combatting the accumulation of marine litter. Australia will enjoy a senior place at future forums and should work to influence and support our regional neighbours to improve their management of the marine environment. Special emphasis should be given to reducing the plastic debris discarded in the oceans and on substantially reducing the quantity of ghost nets.