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Edited by Leon P. Zann
Great Barrier Reef Marine Park Authority, Townsville Queensland
Ocean Rescue 2000 Program
Department of the Environment, Sport and Territories, Canberra, 1995
ISBN 0 642 17406 7
Dr Nigel Wace
Research School of Pacific and Asian Studies
Australian National University, Canberra
Oceans are the ultimate sink for many by-products of human activities, but present data are inadequate to manage this large component of the global commons (Brundtland 1987). Research on ocean pollution has concentrated on the local impacts of diffuse marine pollutants such as oils and other toxins, radionuclides, sewage and other organic wastes, mostly near inhabited coasts in the enclosed seas of the Northern Hemisphere. Conspicuous marine pollutants, including floating marine debris, or ocean litter, have been the subject of conferences in 1985 (Shomura & Yoshida 1985), 1989 (Shomura & Godfrey 1991), and in 1994 (Miami 1994a, 1994b). These have emphasised the detrimental effects of ocean litter on marine wildlife, especially through entanglement (Laist 1994, 1987), ingestion of plastics (Robards et al. 1994), and economic impacts on fisheries and tourism (Miami 1994b). 'Ghost fishing' by abandoned fishing gear results in the entanglement of marine wildlife (Carr & Harris 1994). It is the passive equivalent of drift netting, a wasteful commercial fishing technique which also involves indiscriminate entanglement, and is opposed by Australia.
In Australia, occurrences of ingestion of plastic by seabirds and turtles, and entanglement of cetaceans, seals, seabirds and fish are known, but research has been opportunistic and the overall extent of damage to marine wildlife has not been estimated. The animals mainly affected appear to be the Australian fur seal in Tasmanian waters, and other pinnipeds and cetaceans off Western Australia.
A daily input of more than 600 000 plastic containers into the oceans was attributed to shipping in 1982 and in 1975 the U.S. National Academy of Science estimated that 6.4 million tonnes of litter were jettisoned from ships at sea each year (Laist 1987). Marine pollution from land-based sources (LBS) has been seen mainly in regional terms, but is now a source of global concern (Nollkaemper 1992a). Liffmann (1994) stated that 'not unlike other forms of marine pollution, land based sources [of marine debris] are a much more significant factor than are vessels', and quoted other authors saying that vessels account for only about 10% of all pollutants entering the oceans. A new international convention for the protection of the oceans from all sources of pollution has been mooted (Davis 1990).
International concern about ocean litter led to the Marine Pollution Convention ('MARPOL') regulating the dumping of rubbish at sea, including a total ban on jettisoning plastic. Australia ratified MARPOL in November 1990, but there are presently no data being collected in Australian waters or coasts to discover whether its provisions are having any effect. Recent research in the South Atlantic suggests that they are not (Ryan & Moloney 1993).
There is a general lack of quantitative information about ocean litter, but informed opinion suggests that it is a growing environmental problem worldwide (Miami 1994a, 1994b). This paper discusses some methods of sampling and quantifying ocean litter, the sources of human litter and natural flotsam stranded ashore, the suitability of Australian beaches for monitoring ocean litter, and the movement of floating litter by wind and sea. A summary of what is known about ocean litter on Australian beaches is followed by recommendations for future research and monitoring of stranded litter, as a basis for the enforcement of MARPOL regulations in the seas surrounding Australia.
Ocean litter might be detected and monitored by:
The Marine Debris Survey Manual (Ribic et al. 1992) summarised different techniques, based mainly on experience of such surveys in the North Pacific and North Atlantic.
Remote sensing of floating litter from aircraft or satellites is beyond the capacity of present methods of detection, except for large items in very calm seas, and would not distinguish between natural and synthetic objects. Matsumura et al. (1994) described line transect sightings of 136 000 items of marine debris over 926 000 nautical miles from Japanese fishing vessels in 1987-91, with densities varying from 20-40 items per mile2 in coastal waters and within the Pacific Gyre north of Hawaii, to 0.2 items per mile2 in the North Equatorial Current. Earlier findings from these surveys were mapped by IMO (1991). No such quantitative data are known from sightings of debris in Australian seas. Ship-borne sampling using neuston trawls is a more reliable method of measuring ocean litter at sea, but is slow and costly. Neuston trawling in the surface waters of the New Zealand sector of the Southern Ocean suggested that there were less that 20 items of litter per km2 in seas to the south of the subtropical convergence, and up to some 2000 per km2 in the Tasman Sea (Gregory 1985). Trawl surveys showed that granules from plastic fabrication were locally abundant in seas near manufacturing ports, and may be an underrated contaminant of the oceans (Gregory 1994, 1990). No such trawl surveys have been undertaken in Australian waters.
Systematic beach litter surveys have been used (mostly in North America and Europe) to estimate litter pollution levels in nearby seas. Such beach surveys demand frequent repetition, employing standardised techniques, and a rigorous systematic approach (Ribic 1994; Ribic et al. 1992). Most data on the types and origins of beach litter on Australian mainland coasts are concentrated near cities where land-based litter is most abundant. Greenpeace's Adopt-a-beach litter campaign used survey forms which
'were designed for recreational urban beaches, as opposed to those located near industrial sites. This was because Greenpeace envisaged that people would adopt beaches they visited frequently and, most likely, lived near' (Greenpeace Australia 1992).
Notwithstanding this bias towards popular beaches, Greenpeace paid special attention to 'Debris resulting from fishing practices' and found a total of 34 158 fishing related articles on just 0.8% of the Australian coastline. They tried to distinguish 'hook, line and bait' (HLB) fishing gear (from shore fishing) and maritime 'net fishing' (N) gear, but found it difficult to identify the source of the articles collected. Comparison of Adopt-a-beach yields, with those from remote coasts not visited by beachgoers, could be valuable in sourcing fishing litter, provided the data are collected in comparable ways. Other popular beach-cleaning events such as Clean Up Australia distinguish land-based and marine items in their yields but do not separate the maritime component from litter originating as a result of shore-based fishing. Although valuable in keeping beaches clear of rubbish, Adopt-a-Beach and Clean-up Australia are of limited use in measuring pollution of nearby seas by floating litter. Gregory and Ryan (1994) advocated 'long term monitoring of isolated and remote beaches as a cheap and efficient way of measuring at-sea loads' [of marine debris] and stressed the importance of time-series surveys 'from which accumulation rates can be determined'.
Artifacts stranded on beaches have four possible sources:
Table 1: Composition of the Australian coastline
|% Aust coast
Identifying sources of beach litter is difficult or impossible for items used both ashore and afloat. Features such as buoyancy, purpose and manufacturer; and circumstantial evidence from seasonal timing in relation to shore-bound tourist activity and location, may enable the source of much beach litter to be determined.
Some stranded beach litter comes from natural sources:
geological: pumice, bitumen and tarballs from seabed oil seeps;
plant: seaweed, drift seeds (e.g. coconuts, nickar beans), resins;
animal: cuttlebones, dead fish, seals, cetaceans and seabirds.
Bitumen and tar may have natural or artificial origins (oil spills, tanker washouts). Natural flotsam often carries chemical or taxonomic indications of its source, and thus provides information on the direction from which artifacts entrained in the same water bodies have come. Natural flotsam should therefore be recorded in surveys undertaken to determine the origins of human beach litter.
The Australian coastline has been categorised according to the material at the water's edge, based on a length of about 30 000 km for the continent (Galloway & Bahr 1979). Numbers in Table 1 (Galloway et al. 1984) exclude about 1000 km of water (behind chains of inshore islands), alluvial fans and artificial coasts associated with ports, harbours and sea walls.
Stranded litter is smashed or concealed on rocky coasts, and lost amongst salt marsh plants or mangroves on muddy coasts. Over half the Australian coastline is sandy: it provides the most suitable beaches for observation and monitoring stranded ocean litter.
The preferred characteristics of any beach for ocean litter monitoring can be summarised as:
Collecting and sorting beach litter requires an active, observant and flexible but disciplined labour force. An important practical consideration in selecting a beach for ocean litter monitoring is the accessibility of sources of beachcombing labour, such as local schools. The periodic deployment of such labour can also be used to educate, and promote community involvement in environmental concerns on a global, as well as a local scale.
All beaches absorb continuously varying amounts of energy from the atmosphere and the ocean, including the incessant effects of rhythmic tides. They are therefore in a state of constant flux, within which ocean litter is only a tiny component, caught up in the large scale interactions of wind, sand and sea along the coast. Without some understanding of this dynamic system within which stranded litter is moved and broken down (and eventually becomes incorporated into the coastal sediments), it is impossible to interpret beachcombing yields, and their relation to inputs of litter from the ocean.
Ocean and inshore currents are generally used to indicate the directions from which litter approaches the coastline, and therefore the seas in which it is likely to have been jettisoned. But experiments with drifting objects, and observations of natural flotsam, suggest that wind is often a more important vector than current.
Smith (1991) stated
'Many studies (e.g. Brown 1991, Jokiel 1990) have shown that wind direction provides he best prediction of floating objects' drift speed and direction, at least where currents are not strong. Reported 'surface' currents in generalised maps actually represent integrated transport of all water above the thermocline (Jokiel 1990); those published for mariners and based on ship reports reflect more accurately true surface flows, but they tend to have low levels of constancy (e.g. Federal Dept of Transport, 1987). ... Results of short-term observations of surface water movement (Pickard 1986) and longer-term drift card experiments (Collins & Walker, quoted by Parnell, 1988) in the Great Barrier Reef region are consistent with these generalisations. Floating objects presenting a large freeboard are even more strongly propelled by the wind (Coombs & Landis 1966)'
Figure 1 shows both the major offshore currents and the prevailing winds affecting Australasia, but inshore currents, tidal streams and local winds (e.g. land and sea breezes) fluctuate greatly in strength and direction. The form of coastal dunes, and shape of coastal shrubs can be useful indicators of the dominant inshore wind directions. Wind-driven movements of floating litter may therefore be difficult to predict near the shore, and rafts of litter probably strand episodically, contrary to any predictions based on the major currents and prevailing winds.
Figure 1: Major ocean currents and wind systems influencing Australia
Figure 2: The Australian Exclusive Economic Zone (200 nautical mile) and major fisheries, with numbers of boats involved according to Background Fisheries Statistics No. 6 (Fisheries Policy Branch, Canberrs, August 1992).
Very little systematic or quantitative data are available. Anecdotal accounts suggest that most Australian beach litter of marine origin comes from recreational craft and inshore shipping, and from fisheries on the nearby continental shelf (Figure 2).
Beach litter on the Great Barrier Reef comes from the Coral Sea, Melanesia and the equatorial South West Pacific in the East Australian Current (Creswell 1987). Natural flotsam from Fiji, New Caledonia and Vanuatu drifts westwards across the southern Coral Sea, and is blown towards the coast in the prevailing south-east trade winds. There is an increase in human-derived flotsam, expressed as bottle:coconut ratios, west of the Chesterfield (outermost) Reefs towards Swain Reefs and the central Queensland coast. Pumice on Great Barrier Reef islands and the Australian east coast has been attributed to volcanic eruptions near Tonga and the Kermadec Islands. Plastic containers, rope and thongs are not abundant on cays in the southern Coral Sea, but glass bottles (often Japanese) are common, presumably from shipping and longline and purse seine tuna fisheries (Smith 1992). Cays in East Torres Strait had some glass and plastic bottles in December 1992, with bottle:coconut ratios of 8:55 on three cays (J.M.B. Smith, University of New England, pers. comm.).
Polystyrene floats, fishing litter and bottles were seen at Princess Charlotte Bay in the mid 1980s, but beaches there were generally clear of litter (J. Grindrod, Geography Dept., Monash University, Melbourne, pers. comm.). Nearby Davie and Tydeman Reef Cays, which are probably washed over by storms every few years, had 127 glass bottles, some light globes, thongs and assorted timber on their beaches, together with plastic bottles, pipe, rope, netting and foam in December 1992 (J.M.B. Smith, University of New England, pers. comm.). Daintree beaches were 'remarkably clear' of any litter in September 1992, but some visitors recall much tourist trash there in previous summers. In November 1992, '500 items, plastics predominating' and weighing 8.4 kg, were seen in a litter survey on a 1.1 km length of beach at Deepwater National Park, north of Bundaberg, but this included much tourist trash (Woodall 1993). In south-east Tasmania, 68% of beach litter came from fishing and boating sources in 1990-91. Rope comprised 30% of all plastic beach litter, with large inputs from trawl fisheries and fish farms (Slater l991a, 1991b).
Drift seeds and pumice are carried south in the East Australian Current to beaches in south-east Australia, where they are presumably joined by land litter from the Brisbane, Clarence and Hunter rivers, whose sediment plumes are visible in satellite imagery. Anecdotal evidence from observations along NSW coasts, suggests that plastic and glass bottles are ubiquitous, and that tourist trash is usually abundant and persistent, mixed with estuarine industrial contributions and ocean litter on east coast beaches.
Such fragmentary data give little idea of the quantity of litter on east coast beaches. Data from the Adopt-a-beach clearances on the east coast (where most of this activity has taken place) may yield some information on ocean litter. However the data have not been recorded in a way that litter can be quantified, or the land and marine litter distinguished. In a survey of shoreline litter near Brisbane, Sydney and Melbourne, O'Callaghan (1993) compared beach litter with that in gutters, drains and creeks, and concluded that most stranded litter came from land-based sources. Observers note that littering of beaches in southern NSW varies seasonally and with preceding weather: clear after winter storms, but heavily littered after calm spells in the summer holidays.
South-east trade winds drive surface waters westwards through Torres Strait and between Australia and Indonesia. The South Equatorial Current also sets westward through Indonesia into the Indian Ocean. These flows in the tropics to the north of Australia, contribute to the build-up of waters off north-west WA, forming the headwaters of the Leeuwin Current.
No systematic studies of natural flotsam or synthetic litter are known from beach on these coasts, but anecdotal evidence suggests that away from settlements, fishing litter is abundant. Prawn fisheries in the Gulf of Carpentaria contribute litter which is lost among mangroves, but sandy beaches between the Pellew and Wellesley Islands were badly polluted with fishing gear during the late 1980s, and lesser pollution of beaches in Arnhem Land (west side of Elcho Island, Croker Island, Port Essington, Melville Island and Fog Bay) was noted in the late 1980s to early 1990s. Beaches on the west coast of Bathurst Island remained 'pristine' in 1991, but proposed mineral sand mining there and on Melville Island will lead to future inputs of land-based litter (D. Bowman Northern Territory Conservation Commission, pers. comm.). Land litter on beaches near Darwin is apparently localised, and beach cleanup activities organised. Researchers studying turtle nesting mention Indonesian debris on some northern beaches (D. Curl, Turtle-watcher on Northern Territory coasts, Jabiru, NT0886, pers. comm.).
Table 2: Ocean litter on Australian beaches*
|EAST COAST||NORTH COAST||WEST COAST||SOUTH COAST|
|Arnhem Land||Abrolhos Coast||East Bight||Bass Strait||West Tasmania|
|Dominant current||East Australian Current||Equatorial Counter||Leeuwin||Antarctic Circumpolar Current|
|Direction||N to S||N to S||NE to SW||East-West||North-South||West-East (strongest in winter)|
|Bitumen (seabed seeps)||none||?||?||occasional||?||+|
|Drift seeds & fruits||?||+||coconuts +||coconuts +||Indomalesian||rare||?||rare|
|Human beach litter||(items)||(weight)||(weight)||(items)||(items)|
|Hard plastic (moulded)||} 65%||33% fB||scarce Sf||locally abund.||?||30% Fbsd||38%||}55%|
|Soft plastic (flexible)||} Fb||3% b||scarce f||?||?||} 32%||36%||} Fb|
|Foamed plastic||9%||?5%||rare f||?||?||} Fb||4%||3%|
|Glass||9% B||40% Br||common S||+||?||31% Fbrd||4%||17%|
|Metal||5% B||2% b||very rare f||?||?||5% sb||4%||23% B|
|Wood||(woodchips)||6% s||scarce s||?||?||+ S||+||forest waste|
|Fabrics & footwear||+||8% B||common s||?||?||+ b||+||+|
|Ocean litter surveys||1990-91||1992||1986-1990||10/91,92,93||4-5/93||1990-91|
|Site||south-east||Deepwater NP||Swains Reef||Anxious Bay||Gippsland||SW Heritage|
|Beach length (km)||composite||1.1 km||reefs & cays||26 km||179 km||?|
|Investigator||Slater 1991b||Woodall 1993||Smith 1992||Wace 1994a||Coast Trek||Slater '91b/2|
|Items per km beach||c.300||455||84||350|
|Weight per km beach||7.6 kg||13 - 15kg||7 kg|
|Anecdotal data||Hughes||Nicholson, Grindrod||Smith||Bowman||Wallensky, Minton||Eyre Bird Observatory||Heislers||Wace|
|Litter-generating fisheries||SE trawl, squid||l/l tuna, E trawl||recreational, E tuna||prawn||rock lobster||GAB trawl, SB tuna, squid scallop, shark rock lobster||SE fishery||squid, rock lobster|
* Stranded ocean litter collected from some Australian beaches, based on published and unpublished written accounts of systematic analyses of beachcombings organized by investigators listed, supplemented by anecdotal evidence of beach litter from marine and land sources. Data from Clean-Up-Australia, and Greenpeace's Adopt a Beach activities are not included. The information in this table is not definitive: it categorises and quantifies ocean litter stranded on Australian beaches, to invite the incorporation of more data
Key: Beach litter generators - B=beachgoers; I=urban/industrial; R=recreational craft; F=shelf/inshore fisheries; S=shipping/ferries (upper case for major inputs, lower case for important but lesser contributions to stranded ocean litter); GAB Great Australian Bight; SB Southern Bluefin
Litter on sandy beaches in Roebuck Bay comes from Broome, but Cable Beach nearby is 'very clean'. The northern end of the 80 Mile Beach has 'negligible litter', with some fishing floats, old rope and netting. Plastic bottles and other plastic litter, ropes and nets, are also stranded in small quantities on 80 Mile Beach. Quantities of thick rubber or plastic sheeting, out of which the soles of thongs have been cut, are abundant on Cocos-Keeling Island beaches (E. Wallensky, Australian National University, Canberra, pers. comm.). Such footwear is hand made, and the surplus sheeting jettisoned from Indonesian fishing boats.
Kenneally (1972) recorded seeds and fruits of nine genera of tropical species, probably carried south from Indonesia in the Leeuwin Current and stranded on beaches in south-west Western Australia. Such naturally occurring long distance drift items are now outnumbered by human debris from the offshore rock lobster fishery, and from sources near Carnarvon, Geraldton and Fremantle. The recent discovery of the egg of an extinct elephant bird from Madagascar on an old shoreline near Cervantes, indicates that long distance drifts across the Indian Ocean to Western Australia have taken place in prehistoric times.
The semiarid to arid sandy/aeolianite coast from Geraldton to North West Cape is poorly known. Its ocean litter has not been systematically surveyed, although concern has been expressed over plastic waste and other marine pollutants on this coast (Young 1989). Oceanic litter from the Antarctic Circumpolar Current in the Indian Ocean joins litter from the tropics in the southward-flowing Leeuwin Current, and is deposited on beaches from North West Cape to Shark Bay, and south to Cape Leeuwin and into the Bight (Creswell 1991). Beaches on the Houtman Abrolhos Islands have cray pots, ropes and other debris from the rock lobster fishery, in addition to litter taken ashore by fishers (E. Wallensky, Australian National University, Canberra, pers. comm.).
Strandings of pumice, bottles and drift cards show that a huge area of the Southern Ocean from Australia westwards through the southern Indian Ocean to the Atlantic coast of South America contributes some litter to the south coast of Australia (Wace 1991, 1990). Similar strandings of bitumen and dammar resins indicate Indonesian origins of this natural flotsam (McKirdy et al. 1994; Padley et al. 1993). This oceanic litter and natural flotsam is shepherded southwards along the Indian Ocean coast of Western Australia and into the Great Australian Bight by the Leeuwin Current (Figure 1).
Systematic attempts to identify the types and quantities of ocean litter on a beach remote from human settlements in southern Australia have been made at Eyre Bird Observatory in the western Bight coast, south of Cocklebiddy. Seven clearances of a l km open beach in 1990-91 yielded 494 items, mostly fishing gear: 5% glass, 47% moulded plastic, 41% flexible plastic (including 12% rope), 4% metal and 3% wooden items. Here as elsewhere, plastic forms the major component of ocean litter (Wace 1991; G. Goodried, Curator, Eyre Bird Observatory, pers. comm.). Longshore drift of tourist trash from Twilight Cove to the west may account for some items.
Three clearances of litter along the 26 km beach at Anxious Bay in north-west Eyre Peninsula in October 1991, 1992 and 1993 yielded 343, 399 and 228 kg respectively; averages of 13.2, 15.3 and 8.8 kg of litter per kilometre. About two thirds (by weight) of the Anxious Bay litter consisted of plastic ropes, nets, floats, strapping and containers, mostly abandoned gear from fisheries in the Great Australian Bight including cod-ends and netting from orange roughy and other trawl fisheries, longline floats from tuna boats, rock lobster pots, and bait baskets from inshore fisheries (Wace 1994a; IMO 1992). Yields of ocean litter for these successive October clearances at Anxious Bay should not be interpreted as annual inputs (see table), because an unknown quantity of litter is banked in the beach sands and dunes. Nevertheless, preliminary work for the establishment of a baseline for ocean litter inputs to one large beach in southern Australia has been established. Comparable studies are needed from other coasts. If the Anxious Bay yields typify the contribution of fisheries and shipping to littering Australian beaches, the quantities of marine debris stranding along the whole Australian coastline must be some hundreds of tonnes a year from these sources alone.
In Victoria, beaches west of the entrance to Port Philip Bay, are heavily polluted by plastic food and drink containers, and plastic sheeting and rope. It was estimated that 66% of the plastic rubbish was tourist trash. Some had been washed down the Barwon River from industrial sites in Geelong, but much was foreign, and could be sourced to the visits of particular ships to Melbourne. Plastic pellets from local fabrication plants, plastic fragments in the dunes and beach sands, and the presence of surfactants and foam all form part of a study of beach pollution carried out by Queenscliffe High School students. It illustrates the value of using beach pollution studies in the school curriculum, and the practical difficulty of sourcing beach litter on a densely populated coast near a major port, with tourists, industry, shipping and fisheries all contributing to the mess on these beaches (Hunt & Gray 1990). Many plastic bottles had been chewed by sharks, or nibbled by smaller fish.
Beach litter surveys in November 1991 of 7.2 km of residential and surfing coast east of Port Philip Heads yielded 163 items per km, 69% of which were plastic. Much of the litter was tourist trash. Further east in September 1992, 8 km of beaches not used by surfers yielded 130 litter items per km, averaging 8 kg/km, (75% plastic by number of items, 30% by weight) . A detailed survey of the Gippsland coast in April-May 1993 yielded 84 litter items per km over 179 km of beach (7 kg/km over 67 km where the items were weighed). This comprised about 50% plastic (items and weight) but included land litter left by casual beach users and shore fishers on 90 Mile Beach (D. Heislers, Leader, beach litter surveys on Victorian Bass Strait coasts., pers. comm.).
In Tasmania, 150 surveys of marine debris from 88 beaches all over the State, yielded 50 211 items (January 1990-June 1991), or about 300 items/km. (IMO 1992; Slater 1992, l991b). West coast beaches yielded 300-350 items per km, 61% of which were plastic, and 80% of which originated from offshore fisheries. Seventy nine Adopt-a-beach litter clearances from March to May 1992 yielded 45 515 items of marine debris (about 600 items/km.), but included some heavily populated coasts with litter inputs from land sources and inshore recreational craft (Dick 1992). Plastic items, including rope, strapping bands and fishing nets, buoys and lines, made up 65% of the yield. Inaccessible northern beaches on King Island (Bass Strait) had 10-15 glass bottles per kilometre in April 1994, but very little plastic (Wace 1994c). Tasmanian, Victorian and South Australian data are hard to compare, because urban beaches were included, and litter items were counted (rather than weighed) in the all Tasmanian and most Victorian clearances.
The impacts of litter on marine wildlife seems to have been more intensively studied in Victorian and Tasmanian waters (Pemberton 1992; Slater 1991a; Brown et al. 1986; Skira 1986) than elsewhere on Australian coasts.
Repeated surveys of beach litter on Heard and Macquarie Islands, (where there is no local production of human litter) suggest minimum accumulation rates of 13 items at Heard Island, and 9 per kilometre of coast per year at Macquarie Island (Slip & Burton 1992, 1990). These annual clearances continue, but the beachcombers are having difficulty in removing heavy items which have floated ashore, so that they will not be re-counted in future clearances (N. Perrin, Australian Antarctic Division, Tasmania, pers. comm.). No systematic surveys of beach litter are known from Australian islands in the Indian Ocean or the Tasman Sea. Christmas Island lacks suitable beaches. Local tourist trash may confuse ocean litter signatures on Norfolk and Lord Howe beaches. Casual observations from Cocos-Keeling (E. Wallensky, Australian National University, Canberra, pers. comm.) suggest that they may be good monitoring sites for ocean litter in the north-east sector of the southern Indian Ocean.
From these meagre data, some tentative conclusions are possible concerning the origins, sources, nature, and quantities of ocean litter stranded on Australian beaches:
Table 3: Example of litter survey form format and data
SOUTHERN OCEAN MEGA-LITTER ON AUSTRALIAN STRANDLINES
Anxious Bay, Eyre Peninsula, South Australia
Beachcombers: Australian National University, South Australian Fisheries, Elliston & Streaky Bay schools
Date: 9-15 Oct 1992
|LAND LITTER:(= never-buoyant arEifacts)
few newspapers, 70 unstoppered glass bottles, dirty nappy. few plasticised & waxed cardboard milk & softdrink cartons
GLASS = 123kg (4.7kg/km)
ALUMINIUM (weight included with iron & steel)
RUBBER (weights included with soft plastic)
WOOD (not collected)
CELLULOSE (not weighed)
CLOTH, HESSIAN (not weighed)
TOTALS: 398.7 KG in 26KM = 15.3 kg litter collected per km of beach
NATURAL BEACH LITTER:
|ARTEFACTS: i.e. MANUFACTURED & SYNTHETIC BUOYANT MATERIALS ON BEACH|
HARD (MOULDED) PLASTIC = 121kg (4.7kg/km)
FOAMED AND SOFT (FLEXIBLE) PLASTIC = 126.7kg (4.9kg/km)
|VIRGIN PLASTIC PELLETS: none (but plastic fragments in beach sands)|
Much ocean litter on Australian beaches is jettisoned from fishing vessels near the coast and on the continental shelves, and from shipping using Australian ports. Inshore shipping (and ferries?) probably make the biggest contribution at the approaches to ports, while offshore shipping litter dominates on the Barrier Reef. Most beach litter near cities, and on tourist-frequented coasts has local land-based origins.
Most natural flotsam from outside Australian waters stranding on our coasts, originates in the tropics and is carried south along our west and east coasts by the Leeuwin and East Australian Currents respectively. On tropical coasts, the south-east trade winds force flotsam ashore from the Tasman Sea through the Great Barrier Reef. Some flotsam from middle to high latitudes reaches southern Australia from the South Atlantic and Indian Oceans in the Antarctic Circumpolar Current and the Westerlies. Ocean litter which reaches Australia from distant sources is driven by these surface forces. Although ocean litter from distant sources follows similar courses to natural flotsam, it makes only a tiny contribution to beach litter as compared to that from local sources, especially fishing and coastal shipping. In general, Australians are littering their own beaches with debris jettisoned from vessels operating out of Australian ports, although foreign shipping and fishing vessels may contribute much litter regionally.
The sources of beach litter in Australia are influenced by proximity to cities (as in Israel: Golik & Gertner 1992). On remote coasts, fisheries are the most important beach litter source (as in Alaska: Merrell 1985). Coastal and offshore shipping are important sources at approaches to ports, and along coasts and islands in heavily trafficked seas (as in Western Europe: Dixon & Dixon 1983).
As elsewhere in the world, more than 50% of stranded ocean litter (whether measured by weight or number of items) now consists of plastics, especially rope, netting and fishing gear, and containers (complete or fragmented). Glass objects (bottles, jars, light globes, fluorescent tubes) are ubiquitous but less abundant. Wood, metal, rubber and fabric are usually present in smaller quantities. Driftwood may have maritime or terrestrial origins, but wood may be abundant on beaches near logging operations (Wace 1994b).
The rates and quantities of ocean litter stranding ashore on Australian coasts at any one time, obviously varies widely with situation, season, and preceding weather conditions. Total beach litter yields range up to 500 items or more per km, accumulated over unknown times, but this figure includes some tourist trash. Remote beaches free of tourist trash and other land-based sources, may yield up to 15 kg/km of litter from offshore. Such figures from annual beach clearances can not be accepted as reliable estimates of annual inputs until more studies are made of the rates of natural breakdown and banking of stranded litter. There are no data on which to base reliable estimates of the quantities of litter on beaches, because there is no agreement on the best way to measure it or to distinguish oceanic litter from litter derived locally (i.e. tourist trash, urban, domestic, agricultural, maricultural, industrial wastes).
Australia's geographical position, receiving flotsam and jetsam from the tropical south-west Pacific, and from enormous areas of the Southern Ocean, provides an opportunity to monitor the condition of these seas, as it is registered in the ocean litter cast ashore along our sparsely inhabited coasts. No other southern continent has such a longitudinal extent of ice-free coast. No other continent has poleward flowing currents on both east and west coasts. The major ocean currents approaching Australia deliver flotsam and jetsam from both tropical and high latitude oceans to sandy beaches here where it can be systematically monitored. Anecdotal evidence suggests that most Australian beaches are less strewn with litter than those in corresponding latitudes of the Northern Hemisphere, but that they are more littered than beaches in Fiji and New Zealand.
An Australian beach litter monitoring program could establish important baselines for pollution of the seas around our continent, and in the Southern Hemisphere more generally, and thus contribute to management of the world oceans.
Acknowledgments:I am grateful to Drs Madeline Jones and Jeremy Smith for referees comments, and to Lester Hunt, David Heislers, Janet Slater and others listed in the Table, for unpublished data. The Scientific Expeditions Group, and South Australian Research & Development Institute (Aquatic Sciences) of Adelaide, and the children and their teachers at Streaky Bay and Elliston schools, gave practical assistance in clearances of ocean litter from Anxious Bay. This experience in thrice clearing a major beach of all its litter has been invaluable in compiling this report. I am grateful to all the beachcombers, and to the Federal Government's Ocean Rescue 2000 program for supporting this first attempt to systematically measure the quantity and types of stranded ocean litter anywhere on the Australian mainland coast.
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