Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris
Advice to the Minister for Environment and Heritage from the Threatened Species Scientific Committee on a public nomination of a Key Threatening Process under the Environment Protection and Biodiversity Conservation Act 1999
1. Name and description of the threatening process
Name for the threatening process
The nomination is titled Injury and Fatality Caused by the Ingestion and Entanglement of Marine Life in Marine Debris.
The TSSC considers that those aspects of marine debris and its sources that are known to have an impact on marine species should be considered for listing as a Key Threatening Process. Certain kinds of marine debris, for example floating wooden objects and metal objects which sink and cannot be ingested, will not be harmful to marine life. Further, the TSSC notes that the evidence of threat provided in the nomination is confined to vertebrate marine life. For clarity of intent it is recommended that the nomination be renamed:
'Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris'
Nomination originally submitted for Schedule 3 of the Endangered Species Protection Act, 1992.
Description of the threatening process
The following description is based on that provided in the nomination, with added definitional specifications.
Marine debris is defined by the nomination as the pollution of the marine environment by human generated objects (International Conference on Marine Debris 1994). However TSSC considers marine debris that results from the legal disposal of garbage at sea should be excluded from consideration. For example under the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) overboard disposal of food, paper, glass, metal and crockery is permitted from vessels more than 12 nautical miles from land on the basis, inter alia, that it is not environmentally harmful . Under MARPOL 73/78 there is a total prohibition on the disposal of plastics into the sea, however.
For the purpose of consideration of listing of harmful marine debris as a threatening process TSSC defines harmful marine debris as land sourced plastic garbage, fishing gear from recreational and commercial fishing abandoned into the sea, and ship sourced, solid non biodegradable floating materials disposed of at sea. In concordance with MARPOL 73/78, TSSC defines plastic materials as: bags, bottles, strapping bands, sheeting, synthetic ropes, synthetic fishing nets, floats, fibreglass, piping, insulation, paints, and adhesives. This nomination would also include, under the definition of marine debris, fishing gear such as hooks, fishing line and wire trace.
The threatening process includes entanglement in, and ingestion of, harmful marine debris, as described below.
Marine debris such as fragments of trawl netting, plastic packing straps, and twine or cords cause death or damage to marine species by entanglement. For example death by strangulation can occur to seals as young seals grow with plastic or net fragments entangled around their necks. Extensive wounding to marine animals from fishing line debris, nets or ropes which cuts into the animals skin can lead to infection and eventual death. Entanglement may involve flippers, tails or flukes and may lead to a protracted amputation of limbs. Entanglement in marine debris can also cause restricted mobility, drowning, starvation, and smothering. If the debris is large, it may cause considerable drag as the animal swims, contributing to inefficient hunting and a faster consumption of body reserves.
Harmful marine debris such as plastic bags, rubber, balloons and confectionery wrappers is frequently ingested by marine species, which confuse them with prey species. Most marine species feed non-selectively and may consume marine debris, particularly ones accumulated in the vicinity of food items. This debris usually causes a physical blockage in the digestive system, leading to internal injuries and pain. Turtles frequently ingest plastic bags, confusing them with jellyfish which is common prey for all turtles. Research indicates at least 56 species of sea birds confuse fish eggs and crustaceans with polystyrene balls and plastic buoys, and so consume the debris. Eventual starvation may occur. Autopsies performed by aquaria on marine species such as Grey Nurse Sharks (Carcharias taurus) have found that hook wounds can puncture the stomach, pericardial cavity, and oesophagus causing infection and death. The nomination acknowledges that ingestion of marine debris is difficult to detect and is not widely reported.
The nomination cites a report where the amount of ingested plastic and the levels of polychlorinated biphenals (PCBs) in birds, has been positively correlated. PCBs may be released from plastics ingested by birds and high levels may cause suppression of the immune and reproductive systems, which may threaten species with a low reproductive rate.
2. How judged by EA in relation to the Environment Protection and Biodiversity Conservation Act 1999 criteria
Section 188(4) of the Environment Protection and Biodiversity Conservation Act 1999 states:
A threatening process is eligible to be treated as a key threatening process if:
- it could cause a native species or an ecological community to become eligible for listing in any category, other than conservation dependent; or
- it could cause a listed threatened species or a listed threatened ecological community to become eligible to be listed in another category representing a higher degree of endangerment; or
- it adversely affects 2 or more listed threatened species (other than conservation dependent species) or 2 or more listed threatened ecological communities.
A) Could the threatening process cause a native species or an ecological community to become eligible for listing in any category, other than conservation dependant?
The nomination includes 16 species that it claims could become Endangered or Vulnerable, however no data indicate that any of the nominated species are declining to the extent that they could become so listed.
The nomination cites the Action Plan for Australian Cetaceans 1996 which lists several species that are not yet considered to be threatened due to the lack of sufficient data on the populations. The nomination states that plastic debris and discarded fish nets have been identified as major potential threats for the following species: Fraser's Dolphin (Lagenodelphis hosei); Sperm Whale (Physeter catadon); and Pygmy Right Whale (Caperea marginata).
One expert states that the three largest colonies of the Australian Sea Lion (Neophoca cinerea) are not increasing. Entanglements by animals of this species in marine debris have been documented, however, New Zealand Fur Seal (Arctocephalus forsteri) populations in the same area are increasing.
Conclusion: although the nomination provides data on instances of mortality due to the threatening process, TSSC considers that there is insufficient data or quantifiable evidence to support the view that the threatening process could at the present time cause a native species or an ecological community to become eligible for listing as Extinct, Extinct in the Wild, Critically Endangered, Endangered or Vulnerable. The threatening process is therefore not eligible under this criterion.
B) Could the threatening process cause a listed threatened species or a listed threatened ecological community to become eligible to be listed in another category representing a higher degree of endangerment; or
The Grey Nurse Shark is currently 'vulnerable' but the east coast population has been nominated as 'critically endangered'. Surveys of Grey Nurse Shark in NSW report that approximately 6% of Grey Nurse Sharks sighted show signs of having had interactions with fishing gear. Whilst the latter observations are based on individuals that survive these interactions, it is not known how many die as a result of these interactions. Aquaria experience has found that hook wounds to Grey Nurse Shark can puncture the stomach, pericardial cavity, and oesophagus causing infection and death.
The Action Plan for Australian Cetaceans 1996 identifies entanglement and ingestion of plastics at sea as a current threat to the Humpback Whale Megaptera movaeangliae (Vulnerable), Southern Right Whale Eubalaena australis (Endangered) and Blue Whale Balaenoptera musculus (Endangered). The Australasian population of Blue Whales is estimated at less than 1000. Marine debris is not identified as major threat, but because the populations of these whales are small, the effect of any fatalities on population levels is proportionately large. However, at current population levels the effects of the threatening process are unlikely to lead to the species to be listed in a higher category of endangerment.
The limited studies undertaken in Australia document plastic ingestion by a number of bird species, including Wandering Albatross (Diomedea exulans) and Southern Royal Albatross (Diomedea epomophora), both listed as Vulnerable, and the Northern Royal Albatross Diomedea sanfordi (Endangered). Despite the fact that there is a low number of breeding pairs (approx 15) of the Wandering Albatross, this species is at risk but not thought to be highly threatened by ingestion of plastics (ie not threatened to the extent that it could cause a change to the category of endangerment) due to its feeding habits that largely target squid and fish rather than fish eggs (for which foamed plastic fragments are often mistaken).
Conclusion: Based on the current research the threatening process places some marine animals at risk but there is not enough evidence to suggest that this is likely to cause them to become eligible to be listed in another category representing a higher degree of endangerment. Therefore, TSSC considers that the threatening process is not eligible under this criterion.
C) Does the threatening process adversely affect 2 or more listed threatened species (other than conservation dependent species) or 2 or more listed threatened ecological communities
The nomination includes 30 listed species - 8 endangered, 22 vulnerable - for consideration.
Turtles are known to be at risk from this process. The Draft Recovery Plan for Marine Turtles in Australia (1998) lists the estimated incidences of turtle entanglement and plastic ingestion:
- Hawksbill Turtle, Eretmochelys imbricata (Vulnerable) - annual mortality of North East Australia stock due to ingestion estimated to be in tens, ghost netting mortality estimated to be in the one hundreds.
- Green Turtle, Chelonia mydas (Vulnerable) - annual mortality of southern stock due to ingestion is estimated to be in the tens, entanglement in rope estimated to be ten to one hundred.
- Flatback Turtle, Netator depressus (Vulnerable) - annual mortality due to ingestion and entanglement in ghost netting is known to occur in NT stock.
- Leatherback Turtle, Dermochelys coriacea (Vulnerable) annual mortality due to ingestion is unknown, entanglement substantial in long lines and gill net fisheries.
- Loggerhead Turtle, Caretta caretta (Endangered) annual mortality of eastern stock due to ingestion estimated to be in the tens, as is entanglement in crab float lines.
Marine debris, particularly from discarded fishing nets is a particular problem for turtles. The number of turtles recorded entangled in derelict fishing net at Cape Arnhem (along 50% or 10% of the mainland perimeter of the Gove fisheries statistical area) numbered 18 over a 2 month period in 1998 and 11 over a 2 month period in 1999. The amount of marine debris on the beaches of the Gulf of Carpentaria pose potential hazards to marine turtles, particularly during nesting season. The Hawksbill Turtle, the Green Turtle and the Flatback Turtle have nesting sites within the Gulf.
The Action Plan for Australian Cetaceans 1996 identifies entanglement and ingestion of plastics at sea as a current threat to the Humpback Whale (Vulnerable), Southern Right Whale (Endangered) and Blue Whale (Endangered). The Australasian population of blue whales is estimated at less than 1000. Marine Debris is not identified as a major threat but, because the population is so small, the adverse effect to the population of fatalities caused by marine debris is consequently higher.
Surveys of the Grey Nurse Shark species in NSW (currently listed as Vulnerable but nominated for Critically Endangered) report that approximately 6% of those sighted show signs of having had interactions with fishing gear. These observations are based on individuals that survive these interactions, and it is not known how many die as a result of these interactions. Aquaria experience has found that hook wounds to Grey Nurse Sharks can puncture the stomach, pericardial cavity, and oesophagus causing infection and death.
Interactions by sharks with “ghost nets” have been recorded but the resultant mortality remains completely unknown for Australian shark species.
Albatrosses and petrels
Most marine debris affecting albatrosses and petrels appear to derive from material jettisoned by vessels at sea. Many albatross and petrel species ingest considerable quantities of plastic and other marine debris. Ingestion of debris has a wide range of lethal or sub-lethal effects. The debris can cause physical damage, or perforation, mechanical blockage or impairment of the digestive system, resulting in starvation. Some plastics are also a source of toxic pollutants such as PCBs, which are released into the blood stream as the bird's digestive system attempts to break down the substance. The subsequent reduction in fitness can lower the bird's ability to reproduce successfully, catch prey and/or avoid predators.
Chicks appear to be at greater risk than adults because of their high rates of ingestion and low frequency of regurgitative casting of indigestible material. When the plastics are regurgitated to chicks, the physical impact and internal ulceration are likely to lower survival. In addition, the chick receives less food, lowering its nutrient intake and increasing its chances of starvation. The problem of plastic ingestion may affect many Australian breeding species of albatrosses and petrels. In a study of the stomach contents of 540 Shy Albatross (Diomedia cauta) chicks that had recently died of natural causes, 1% of stomachs contained plastic debris, ranging from segments of plastic bags to solid, coloured pieces of plastic. Wandering and Grey-headed Albatrosses and Southern Giant-Petrels have all been observed regurgitating plastic debris to their chicks on breeding sites outside of Australia.
Several 'foraging only' species, including Antipodean (Diomedea antipodensis), Gibson's (Diomedea gibsoni), Tristan (Diomedea dabbenema), Northern Royal, Southern Royal and Indian Yellow-nosed Albatrosses (Thalassarche carteri) have been observed regurgitating plastic debris to their chicks. It is likely that most or all other 'foraging only' species ingest plastic debris without it being observed or documented.
Both the Northern Giant Petrel (Macronetes halli) and the Wandering Albatross (both listed as Vulnerable) are identified in relevant action plans and recovery plans as under threat from ingestion of marine debris (plastics and hooks which are regurgitated to the chicks). Species with low numbers of breeding individuals which include the Wandering Albatross which has only 15 breeding pairs, or small populations such as Gould's Petrel Pterodroma leucoptera leucoptera (listed as Endangered), Grey-Headed Albatross (Thalassarche chrysostoma), and Blue Petrel (Halobaena caerulea) (both listed as Vulnerable) are at risk.
Some seabirds are also killed after becoming entangled in marine debris. Such entanglement can constrict growth and circulation, leading to asphyxiation. Entanglement may also increase the bird's drag coefficient through the water, causing the animal to die due to its reduced ability to catch prey or avoid predators. The rate of this source of mortality remains completely unknown for Australian species.
The TSSC considers the following Endangered species and Vulnerable species listed under the Environment Protection and Biodiversity Conservation Act 1999 to be adversely affected by the threatening process:
- Loggerhead Turtle
- Southern Right Whale
- Blue Whale
- Tristan Albatross
- Northern Royal Albatross
- Gould's Petrel
- Leatherback Turtle
- Hawksbill Turtle
- Flatback Turtle
- Green Turtle
- Wandering Albatross
- Humpback Whale
- Antipodean Albatross
- Gibson's Albatross
- Southern Royal Albatross
- Indian Yellow-nosed Albatross
- Grey Nurse Shark
- Grey-headed Albatross
- Blue Petrel
- Northern Giant Petrel
Conclusion: It is considered that marine debris that are sourced from land based plastics, fishing gear from recreational and commercial fishing and ship sourced, solid non biodegradable materials disposed of at sea does adversely affect two or more listed marine species. It is important to note that this is not the only threat to these species and that the relative magnitude of the threat from marine debris, as defined, is not certain when compared with other processes, such as long-line fishing (which affects albatrosses) and indigenous harvesting of turtles. However, a precautionary approach to the issue leads to the conclusion that, even in the absence of clear scientific evidence that the named species are affected at the level of populations, it is reasonable to state that the named species are adversely affected by the threatening process, especially when its effects are combined with those of other threatening processes. Therefore TSSC considers the threatening process is eligible under this criterion.
Conclusion - The threatening process 'Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris' adversely affects at least 20 listed threatened species. The threatening process therefore meets s188(4)(c) of the EPBC Act.
3. Threat Abatement Plan
The nomination suggests that a coordinated threat abatement plan could be an effective and efficient means of abating the threatening process by incorporating action to address both land based and shipping and boating sources of marine debris. Some experts, including a number that do not support the nomination, support the need for action in these areas, in addition to current mitigation activities.
Current mitigation activities are wide ranging, and include: government programs to improve waste retrieval from watercourses (Victorian Stormwater Action Program, Commonwealth Coasts and Clean Seas Initiatives and Urban Stormwater Initiative); anti-littering laws; laws controlling overboard disposal of ship and boat generated garbage including fishing gear (implementing Annex V of the international MARPOL 73/78 Convention); programs for the improvement and greater use of on-shore reception facilities for marine waste (Commonwealth Marine Waste Reception Facilities Program and ANZECC Best practice guidelines for marine waste reception facilities – 1997); and codes for responsible conduct in the fishing industry.
These go some way towards addressing the issue of marine debris, however the link between marine debris and its impact on marine wildlife is not a significant consideration in the design or implementation of current mitigation activities. Several experts raised the need for greater enforcement of, or compliance with, existing measures as a way of dealing with marine debris more fully. In addition, a review of existing instruments, such as MARPOL 73/78, and issues of compliance and local government initiatives, would be important in determining if they were being successful in reducing the impacts of marine debris.
A Threat Abatement Plan specifically related the effects of marine debris on vertebrate marine life would bring together abatement strategies identified in marine animal Recovery Plans such as the Marine Turtle Recovery Plan, the Recovery Plan for Albatross and Giant Petrels, and the Grey Nurse Recovery Plan. It should also review existing policies, codes of practice, conventions and actions to determine their effectiveness. One of the major inclusions in the Threat Abatement Program would also be an examination of the effectiveness of , or need for, joint agreements with other nations to specifically address the issues of marine debris and its impact on marine wildlife.
Conclusion: The TSSC consider a Threat Abatement Plan to be a feasible, effective and efficient way to abate the threatening process.
- The TSSC recommends that the name of the threatening process be altered to 'Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris'.
- The TSSC recommends that the list referred to in section 183 of the EPBC Act be amended by including in the list as a key threatening process: 'Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris' as described in this advice.
- The TSSC recommends that a Threat Abatement Plan is a feasible, effective and efficient way to abate the threatening process.
Publications used to assess the nomination
- ANZECC Working Party on Marine Debris (1996) Final Report The Australian Marine Debris Status Review, Maunsell Pty.
- Baker G.B, Gales R, Hamilton.S, Wilkinson V. (2001) Albatrosses and Petrels In Australia: A Review of Their Conservation and Management (in press) Environment Australia.
- Bannister J.L, Kemper C.M, Warneke R.M (2001) The Action Plan for Australian Cetaceans, Environment Australia.
- Crowley G.M, Garnett S.T, (2000) Action Plan for Australian Birds Environment Australia.
- Environment Australia (2000) Draft Grey Nurse Shark Recovery Plan Environment Australia
- Environment Australia (2000) Draft Marine Turtle Recovery Plan Environment Australia
- Environment Australia (2001) Recovery Plan for Albatrosses and Giant Petrels, Environment Australia.
- Environment Australia (2001) Draft Recovery Plan for Southern Right Whales in Australian Waters, Environment Australia.
- Environment Australia (1999) Draft Recovery Plan for Blue Whales in Australian Waters, Environment Australia.
- Kiessling, I. April 2001 Impacts of Marine Debris in the Regional Marine Environment World Wide Fund for Nature, Australia Indonesia-Australia Conference and Exhibition on Marine Resources Cooperation Aligning the Development of Regional Marine Resources
- Leitch, K. 1998. Entanglement of Marine Turtles in Netting: Northeast Arnhem Land, Northern Territory, Australia. Report to World Wide Fund for Nature Australia, Dhimurru Land Management Aboriginal Corporation, Northern Territory.
- Leitch, K. 1999. Entanglement of Marine Turtles in Netting: Northeast Arnhem Land, Northern Territory, Australia. Report to World Wide Fund for Nature Australia, Dhimurru Land Management Aboriginal Corporation, Northern Territory.
- Shaughnessy P.D, (1999) The Action Plan for Australian Seals, Environment Australia.
- Website of the International Marine Debris Conference, August 2000 Hawaii www.hihwnms.nos.noaa.gov