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From castaways to throwaways: marine litter in the Pitcairn Islands
Biological Journal of the Linnean Society (1995), 56: 415–422.
The Pitcairn Islands: biogeography, ecology and prehistory Edited by T. G. Benton and T. Spencer
From castaways to throwaways: marine litter in the Pitcairn Islands T. G. BENTON University Museum of Zoology, University of Cambridge, Downing St., Cambridge, CB2 3EJ and School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ 1
Pollution of the oceans by garbage is a serious problem. Worldwide, as many as 8 million items of garbage may enter the seas on a daily basis. These items may survive some time, drifting in the oceans and give rise to other environmental problems such as causing hazards to wildlife (through ingestion and entanglement) before being washed ashore. Surveys of beaches on Ducie and Oeno Atolls in the Pitcairn Islands were compared with a similar survey on a beach in S.W. Ireland. The three beaches were similar in the density and major categories of garbage to be found, but differed in subtle ways. For example the Pacific beaches had a greater proportion of bottles and buoys, whereas the Irish beach had a greater proportion of sweet wrappers and polythene bags. Although these remote islands may be thousands of miles from industrial centres their beaches are apparently as dirty as those in Europe. © 1995 The Linnean Society of London
ADDITIONAL KEY WORDS:*garbage – rubbish – pollution – Pacific – coasts – beaches – Ducie Atoll.
CONTENTS Introduction . . . Methods . . . . Ducie Atoll . . Oeno Atoll . . Inch Strand, Ireland Results . . . . Discussion . . . Acknowledgements . References . . .
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415 417 417 417 417 417 420 422 422
INTRODUCTION
For most of history, the oceans of the world have been seen as a vast waste-disposal device, into which any amount and type of waste could be 1
Current address, and address for correspondence: 3 Kesters Close, Hardwick, Cambridge CB3 7QY.
0024–4066/95/090415+08 $12.00/0
415
© 1995 The Linnean Society of London
416
T. G. BENTON
successfully disposed without problems (Gregory, 1990a). Large oil and chemical spills create headline news for their environmental impact, but the more insidious day-to-day abuse of the ocean lacks sufficient impact to be brought to public attention. This day-to-day abuse is not small scale. Horsman (1982) estimated that 6.8 million metal, 426 000 glass and 639 000 plastic containers (including bags) were dumped at sea on a daily basis from merchant ships alone. Annex V of the International Convention for the Prevention of Pollution from Ships (MARPOL) forbids the disposal of plastics in the oceans from ships, and set minimum distances from land inside which other types of garbage cannot be disposed. Although often illegal, marine disposal of garbage continues. Also continuing is the disposal of garbage from land into the oceans. This occurs through littering of beaches by tourists (Pruter, 1987), outfall from factories (Gregory, 1978), rivers (Pruter, 1987) and sewage (Ye & Andrady, 1991). Garbage entering the oceans may survive for considerable periods. This is especially true of some plastics, such as monofilament netting and polypropelene cordage, which may last over 50 years (Gregory, 1990a), though many plastics will survive for shorter periods (Gregory 1983; Dixon & Dixon, 1981). Glass objects may presumably also last considerable lengths of time. Much garbage also has positive buoyancy, so will drift around on the oceans (Ye & Andrady, 1991) until it disintegrates, sinks, washes ashore or is eaten by marine organisms. Ingestion of plastics by marine organisms is common and has been reported in over 50 species of birds (Fry, Fefer & Sileo, 1987; Gregory, 1990a), cetaceans, manatees (Laist, 1987) and turtles (Bjorndal, Bolton & Lageux, 1994). Ingestion of plastics may prove fatal if the gut becomes blocked (Laist, 1987; Bjorndal et al., 1994), or if toxic chemicals leach from the garbage (Merrell, 1980). Additionally, entanglement in debris (especially discarded fishing gear, plastic strapping bands, beer-can yokes, etc.) is a serious problem for many species of marine mammals, birds, turtles and fish (Laist, 1987). Upon washing ashore the hazard of garbage does not end. Beachgoers may face injury from broken glass or medical equipment (Dixon & Dixon, 1981), and terrestrial organisms may ingest garbage on the beaches (Merrell, 1980). It is difficult to assess the amount of garbage on the oceans directly (Dixon & Dixon, 1981), whereas it is not difficulty to assess the quantities of litter on beaches. Beach surveys provide valuable information on the amounts and types of garbage in the oceans. This is especially true of more remote beaches as these do not suffer from local land-based pollution, so the information gained can be used to assess garbage longevity. The Pitcairn Islands are amongst the most remote in the world (being over 4500 km from the nearest continental landmass), and of these, the most remote of the islands is Ducie Atoll (24°40?S, 124°47?W) which is 472 km away from the nearest inhabited island (Pitcairn, population c. 50), and is rarely visited by passing yachts (it has no fresh water or sheltered anchorage). Oeno Atoll (23°56?S, 130°45?W) is nearer to Pitcairn (some 160 km) and so is periodically visited by the islanders for their ‘holidays’ but, like Ducie, is rarely visited by passing yachts. Thus, anthropogenic garbage on these beaches is most unlikely to be locally produced, and most likely to have drifted considerable distances before being deposited on the beaches. In comparison, the litter
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found on many beaches in populated parts of the world is often of local origin. To illustrate this comparison, beach-litter surveys are presented here for Ducie, Oeno and a beach in south-west Ireland (Inch Strand, Dingle Peninsular, Co Kerry, Eire: GR 660980). METHODS
Ducie Atoll The survey was conducted on 28 and 29 March 1991. The seaward beach of the largest motu in the Atoll, Acadia Island, was surveyed as a continuous belt transect some 4000 m long (M. Brooke, personal communication) (see Spencer 1995, Fig. A4). Approximately one third of this beach faces the prevailing winds, whereas the remainder lies roughly parallel to the wind. Objects within a 2 m wide strip were noted. The beach on the seaward side of Acadia is steep, narrow and consists largely of coarse coral rubble. Thus small objects are often hidden between lumps of rubble and may be underrepresented in the sample. Oeno Atoll This survey was conducted by Dr Richard Preece and Sue Schubel in November 1991. An area (500 m×5 m) of beach on the sandy spit (see Spencer 1995, Fig. A3) was exhaustively searched to ensure all objects of anthropogenic origin within the area (approximately 2500 m2) were noted. The searched area was on the leeward side of the spit, in the centre of the lagoon, and consisted of banked coral sand. Inch Strand, Ireland A single belt transect was conducted along the upper shore on 25–26 September 1993. This transect was calculated to be 891 m (1100 paces at an average of 81 cm per pace). Objects within 2 m either side of my track were noted. Inch Strand is a depositional beach, facing into the Atlantic and the prevailing winds. The beach is backed by high (up to 30 m) dunes. Prior to the survey there had been strong onshore winds, which caused much drifting of sand up the beach. Thus, again, small items may be underrepresented in this sample, as they were more likely to be buried completely. RESULTS
The absolute amount of garbage in the three locations of Ducie, Oeno and Inch is frighteningly large (Table 1). On Ducie there were approximately 0.12 pieces of garbage m−2 beach surveyed, on Oeno, 0.35 pieces m−2 and on Inch Strand 0.22 m−2. Thus, in the remote South Pacific there are similar levels of garbage on the beaches to those found on a beach in populated and industrialized Europe. The proportions of garbage of different types is also remarkably similar between the islands in the Pitcairn Group and the beach in Ireland (Table
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TABLE 1. The major categories of marine litter on the three beaches surveyed. Single items, not fitting in any category, may be excluded from this table. The data from Ducie was originally published in Benton (1991). * indicates category included in statistical analysis (‘common rubbish’, where total found on all three beaches ×15 items). + indicates a single plastic bin-liner was also found containing an estimated 30 used nappies ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Ducie Oeno Inch Category n % n % n % ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — * Unidentified and misc. plastic 268 28 305 35 182 20 * Buoys (and bits) 179 19 67 8 28 3 * Glass bottles 171 18 148 17 54 6 * Bottle tops 74 8 76 9 55 6 * Plastic bottles 71 7 62 7 94 11 * Cord:rope 44 5 51 6 103 12 * Plastic pipe fragments 29 3 26 3 4 ³1 * Shoes 25 3 7 ³1 2 ³1 * Glass jars 18 2 — — 11 1 Crates (for food and drink) 14 1 — — 1 ³1 Aerosol cans 7 ³1 4 ³1 4 ³1 * Food tins:drink cans 7 ³1 7 ³1 17 2 * Light bulbs 6 ³1 31 4 1 ³1 * Fluorescent tubes 6 ³1 22 3 — — Cigarette lighters 3 ³1 5 ³1 3 ³1 Pen tops 2 ³1 3 ³1 — — Plastic strapping — — 16 2 21 2 * Cut wood — — 6 ³1 15 2 Bits of bucket — — 5 ³1 2 ³1 * Polythene bags — — — — 106 12 * Sweet:crisps wrappers — — — — 34 4 Disposable nappies — — — — 13+ 1 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Other items (total found) 27 (951) 37 (878) 44 (794) Density (items m−2) 0.12 0.35 0.22 0.24 1.76 0.89 Estimated items linear m−1 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– —
1). To assess the similarity of the beaches, I ranked the 15 most common categories of rubbish (from Table 1) and calculated Spearman’s rank-order correlation between the three possible pairwise combinations of the three beaches: Ducie vs Oeno, rs 0.876, P ³ 0.001; Ducie vs Inch, rs 0.393, P × 0.1; Oeno vs Inch, rs 0.352, P × 0.2. Thus, the proportions of rubbish in the different categories are similar on Ducie and Oeno, but less so in Inch. However the low correlations between the Pacific and European beaches are caused by two points only: those for polythene bags and sweet:crisp wrappers. Removal of these categories from the analysis gives: Ducie vs Oeno, rs 0.82, P ³ 0.002; Ducie vs Inch, rs 0.73, P ³ 0.01; Oeno vs Inch, rs 0.68, P ³ 0.02. Therefore, leaving aside polythene bags, sweet wrappers and uncommon items, each beach is broadly similar in the rank-order of rubbish categories; rubbish common on one beach tends to be common on the others (e.g. pieces of plastic, glass bottles, etc), whereas rubbish rare on one beach also tends to be rare on the others (e.g. shoes, jars, tin cans, etc). To investigate this more exhaustively, the 15 common categories were analysed using a Chi-square contingency table to assess whether there were associations between beaches and litter types. As expected, the overall Chisquare is highly significant (Chi-square 710, df 28, P ³ 0.0001). However,
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TABLE 2. Some oddities from the three beaches ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Ducie Oeno Inch ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — tinned meat pie, intact, but leaking bicycle pedal veterinary examining glove (elbow length) dolls’ heads (male+female) toy car used syringes (5) toy aeroplane toy aeroplane window frame football baby’s dummy measuring cylinder plastic skittle screwdriver car seat asthma inhaler candle wax used hypodermic needle tea strainer tea strainer suitcase handle letter in wine bottle* shotgun cartridge lego brick ‘Watney’s’ beer barrel* egg carton car foot-mat car foot-mat toy soldiers (2) plastic hair curlers ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — * Found on Ducie, but not on the reported transect.
what is of interest are the component chi-squares for each category as these illustrate which beaches differ from the others. If all the beaches were identical, then rubbish would distribute itself similarly between beaches. Thus, the analysis highlights where rubbish in each category is more or less common than expected. Polythene bags are much more common than expected at Inch; buoys are much more common on Ducie, slightly less common on Oeno and much less common in Inch; sweet wrappers are much more common at Inch; string:cord and rope are much more common at Inch; bulbs and fluorescent tubes are significantly more common on Oeno compared with the other two; the reverse is true for glass jars and plastic fragments; glass bottles are significantly rarer in Inch than the Pacific, whereas the reverse is true for plastic bottles; shoes are more common on Ducie; tin cans are more common in Inch, as is cut wood; bottle tops are equally common on all three beaches. Thus, as well as similarities, there are differences between the beaches in the proportions of rubbish in the common categories. However, it is not solely the amount of rubbish that is of some interest, but also its diversity. In this respect all three beaches have a similar diversity (Table 2); it is just that, especially on the remote Pacific beaches, this diversity is most unexpected for someone naive of the literature (e.g. Pruter, 1987; Gregory, 1990b). Given that most garbage must drift considerable distances to land on Ducie and Oeno, it is remarkable that such items as toys, footballs, tea strainers, car foot mats and so on survive to drift ashore. The country of origin was determined for a sub-sample of 130 glass bottles on Ducie (Table 3). The single most common country of origin was Japan and the most common type of bottle once contained whisky (especially Suntory Whisky from Japan). The diverse origins of these bottles makes it unlikely that they drifted from their countries of origin, but were most likely dumped at sea. However, the commonness of pieces of pumice and tree-fern logs on the Pitcairn Islands, which are both likely to originate in South America, testifies to the possibility of long-distance oceanic travel (see Jockiel, 1989). Long distance is however relatively unlikely for any given piece of garbage, with many items sinking, degrading, being ingested or washing ashore for each piece remaining afloat for great lengths of time. On the whole of Inch Strand I encountered only
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TABLE 3. Origins of a sample of 130 glass bottles from beach on Acadia Island, Ducie. The diversity implies that many were disposed of from boats, rather than drifting from source countries –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Country n Comments –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Japan 41 mainly Suntory whisky Unidentified 35 4 beer, others mainly wine Scotland 11 all whisky UK 9 whiskys + Harvey’s sherry USA 8 mainly Schweppes soft drinks ? South America 4 labelled in Spanish:Portuguese Germany 3 soft drinks New Zealand 3 France 2 brandy Holland 2 Russia 2 1 vodka Venezuela 2 Italy 1 wine Spain 1 Portugal 1 Argentina 1 –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– —
12 pieces of garbage likely to be long-distance drifters (as assessed by epifaunal community as well as the country of origin): Spain:Portugal 6, France:Belgium 3, Morocco 1, US 2). If I generalize the estimate of garbage density (from the surveyed 891 m) to the whole of Inch Strand (5.4 km), then only about 1 item in a 1000 to land on the beach has drifted long distance. As items have to drift long-distances to wash ashore in the Pitcairn Islands, then to account for the presence of so much rubbish on the beaches, perhaps 1000 items thus have to be thrown into the ocean for every one encountered on the beach. DISCUSSION
The major, and somewhat alarming, conclusion from this study is that beaches in the remote South Pacific have a comparable amount of garbage to a beach in the industrialized western world. In 1993, 1238 volunteers collected rubbish on 121 beaches around the UK, as part of ‘Beachwatch 93’. These collections cleaned entire widths of shore, whereas the Ducie and Inch surveys reported here only noted rubbish in a narrow band along the strand line, and so surely underestimate the total number of items per linear metre of beach. However, the median items per linear metre for beaches in the UK is 0.52 (range 0.137–9.83) (data from McGilvray, 1994). In comparison, the data presented here represent estimates of 0.24 (Ducie), 0.89 (Inch) and 1.76 (Oeno). So, although the beaches in Ducie and Oeno are rarely visited by humans, and are thousands of kilometers from the nearest industrial centres they are as dirty as other areas of the world. Sadly, it is well known that many remote Pacific islands are strewn with litter washed ashore (Gregory, 1990b), and the same applies to other remote locations in the world (Merrell, 1980; Gregory, 1990a). It is also unfortunate to note that during a visit to Ducie at the end of July 1992, members of the Expedition
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found large amounts of tar on the beaches, presumably caused by a tanker illegally washing out its tanks in mid-ocean (M. Brooke, personal communication). The pollution on beaches, as well as being unsightly, also poses a threat to wildlife. Imber, Jolly & Brooke (1995) found that petrels on Ducie had sometimes ingested plastics, and the green turtles on Henderson (Brooke, 1995) may also be at risk (Bjorndal et al., 1994). However, this flotsam may also, more rarely be of use to local wildlife. On Henderson, land hermit crabs (Cenobita sp.), were occasionally found to select items of garbage (such as the lids of aerosol cans, heels of shoes etc.) as shelters rather than the more traditional shells. Additionally, flotsam floating in the oceans may serve as rafts allowing the dispersal of a wide range or organisms (e.g. Jockiel, 1989); many items encountered on the beaches of Henderson and Ducie had often extensive epifaunal communities of barnacles, bryozoans and corals. Although broadly similar in garbage densities, the beaches of the Pacific differ from the beach in Ireland in subtle ways. In Ireland, there was an excess of locally-produced non-durable material (such as sweet wrappers, plastic bags, tin cans, disposable nappies etc). Conversely, in the Pacific there was an excess of the more durable items (especially glass bottles and buoys). The more easily degraded litter, found in Ireland, presumably does not survive sufficient periods to drift to the more remote locations; and much of the useful, durable, flotsam (e.g. intact buoys) found in the Pacific may be removed by beachcombers in Ireland and other populated parts of the world (indeed, the Expedition made considerable use of items of flotsam, using buoys for constructing moorings, wood and plastic for furniture, and a plastic funnel to make equipment for extracting insects from soil). However, the presence of plastic bottles of considerable age on Inch Strand (as denoted by the chalky, friable appearance of the plastic) attests to some considerable longevity of some items. It should be noted that the differences between the two beaches in the Pacific may be as great as the differences between the Irish and Pacific beaches. Just as Inch has an excess of flimsy plastics, Oeno has an excess of light bulbs and fluorescent tubes, and Ducie has an excess of jars, buoys and shoes. Thus each beach is unique, and the differences between them are perhaps more subtle than may have been expected from their locations in the remote Pacific and polluted Europe. The overall similarity of garbage between the three beaches perhaps testifies to similar sources. Much of the garbage, perhaps most of it, undoubtedly comes from marine dumping. Ships sailing between Australia:New Zealand and Panama may pass quite close to the Pitcairn Islands, and many vessels sail the North Atlantic. This ship-produced garbage is supplemented in Ireland by the garbage of beachgoers and local people (many domestic refuse sacks appear to be dumped over cliffs directly into the sea). The beaches of the remote Pacific, rarely visited by humans, carry as much garbage as beaches in more industrialized areas in Europe (Ireland: this study: UK: McGilvray, 1994; Mediterranean: Gabrielides et al., 1991). Thus, even though these areas are not inhabited they suffer the long-distance pollution from the inhabitants of other places. The animals on these remote islands may have little chance of encountering humans, but every chance of encountering the life-threatening waste we generate.
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I would like to thank Richard Preece and Sue Schubel for doing a rubbish survey on Oeno, the University of East Anglia for having an ecology fieldcourse in Inch, Peter Jones and Mike Brooke who originally suggested my garbage notes might be worth publishing, and Murray Gregory for constructive comments on an earlier version. My visit to the islands as part of the Sir Peter Scott Commemorative Expedition was generously supported by the following major sponsors: The Royal Society, International Council for Bird Preservation, British Ornithologists’ Union, J. A. Shirley, Foreign & Commonwealth Office UK, UNESCO; all other sponsors are acknowledged in the expedition report of 1992. This is paper 52 of the Sir Peter Scott Commemorative Expedition to the Pitcairn Islands. REFERENCES Benton TG. 1991. Oceans of garbage. Nature 352: 113. Bjorndal KA, Bolten AB, Lageux, CJ. 1994. Ingestion of marine debris by juvenile sea turtles in coastal Florida habitats. Marine Pollution Bulletin 28: 154–158. Brooke MdeL. 1995. Seasonality and numbers of green turtles Chelonia mydas nesting on the Pitcairn Islands. Biological Journal of the Linnean Society 56: 325–327 Dixon TR, Dixon TJ. 1981. Marine litter surveillance. Marine Pollution Bulletin 12: 289–295. Fry DM, Fefer SI, Sileo L. 1987. Ingestion of plastic debris by Laysan albatrosses and wedge-tailed shearwaters in the Hawaiian Islands. Marine Pollution Bulletin 18: 339–343. Gabrielides GP, Golik A, Loizides L, Marino MG, Bingel F, Torregrossa MV. 1991. Man-made garbage pollution on the Meditterranean coastline. Marine Pollution Bulletin 23: 437–441. Gregory MR. 1978. Accumulation and distribution of virgin plastic granules on New Zealand beaches. New Zealand Journal of Marine and Freshwater Research 12: 399–414. Gregory MR. 1983. Virgin plastic granules on some beaches of eastern Canada and Bermuda. Marine Environmental Research 10: 73–92. Gregory MR. 1990a. Environmental and pollution aspects. In: Glasby, EP, ed. Antarctic sector of the Pacific. Elsevier Oceanography Series 51: Amsterdam: Elsevier. 291–324. Gregory MR. 1990b. Plastics: accumulation, distribution, and environmental effects of meso-, macroand megalitter in surface waters and on shores of the southwest Pacific. In: Shomura RS, Godfrey ML, eds. Proceedings of the Second International Conference on Marine Debris, 2–7 April 1989, Honolulu Hawaii. US Department of Commerce, NOAA Technical Memo: NMFS, NOAA-TM-NMFS-SWFSC154. Horsman PV. 1982. The amount of garbage pollution from merchant ships. Marine Pollution Bulletin 13: 167–169. Imber M, Jolly JN, Brooke MdeL. 1995. Food of three sympatric gadfly petrels (Pterodroma spp.) breeding on the Pitcairn Islands. Biological Journal of the Linnean Society 56: 233–240. Jockiel PL. 1989. Rafting of reef corals and other organisms of Kwajalein Atoll. Marine Biology 101: 483–493. Laist DW. 1987. Overview of the biological effects of lost and discarded plastic debris in the marine environment. Marine Pollution Bulletin 18: 319–326. McGilvray F. 1994. Beachwatch 1993. Ross-on-Wye, Herefordshire: Marine Conservation Society:Reader’s Digest. Merrel TR. 1980. Accumulation of plastic litter on beaches of Amchitka Island, Alaska. Marine Environmental Research 3: 171–184. Pruter AT. 1987. Sources, quantities and distribution of persistent plastics in the marine environment. Marine Pollution Bulletin 18: 305–310. Spencer T. 1995. The Pitcairn Islands, South Pacific Ocean: plate tectonic and climatic contexts. Biological Journal of the Linnean Society 56: 13–42. Ye S, Andrady AL. 1991. Fouling of floating plastic debris under Biscayne Bay exposure conditions. Marine Pollution Bulletin 23: 608–613.
The Pitcairn Islands: biogeography, ecology and prehistory Edited by T. G. Benton and T. Spencer
From castaways to throwaways: marine litter in the Pitcairn Islands T. G. BENTON University Museum of Zoology, University of Cambridge, Downing St., Cambridge, CB2 3EJ and School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ 1
Pollution of the oceans by garbage is a serious problem. Worldwide, as many as 8 million items of garbage may enter the seas on a daily basis. These items may survive some time, drifting in the oceans and give rise to other environmental problems such as causing hazards to wildlife (through ingestion and entanglement) before being washed ashore. Surveys of beaches on Ducie and Oeno Atolls in the Pitcairn Islands were compared with a similar survey on a beach in S.W. Ireland. The three beaches were similar in the density and major categories of garbage to be found, but differed in subtle ways. For example the Pacific beaches had a greater proportion of bottles and buoys, whereas the Irish beach had a greater proportion of sweet wrappers and polythene bags. Although these remote islands may be thousands of miles from industrial centres their beaches are apparently as dirty as those in Europe. © 1995 The Linnean Society of London
ADDITIONAL KEY WORDS:*garbage – rubbish – pollution – Pacific – coasts – beaches – Ducie Atoll.
CONTENTS Introduction . . . Methods . . . . Ducie Atoll . . Oeno Atoll . . Inch Strand, Ireland Results . . . . Discussion . . . Acknowledgements . References . . .
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415 417 417 417 417 417 420 422 422
INTRODUCTION
For most of history, the oceans of the world have been seen as a vast waste-disposal device, into which any amount and type of waste could be 1
Current address, and address for correspondence: 3 Kesters Close, Hardwick, Cambridge CB3 7QY.
0024–4066/95/090415+08 $12.00/0
415
© 1995 The Linnean Society of London
416
T. G. BENTON
successfully disposed without problems (Gregory, 1990a). Large oil and chemical spills create headline news for their environmental impact, but the more insidious day-to-day abuse of the ocean lacks sufficient impact to be brought to public attention. This day-to-day abuse is not small scale. Horsman (1982) estimated that 6.8 million metal, 426 000 glass and 639 000 plastic containers (including bags) were dumped at sea on a daily basis from merchant ships alone. Annex V of the International Convention for the Prevention of Pollution from Ships (MARPOL) forbids the disposal of plastics in the oceans from ships, and set minimum distances from land inside which other types of garbage cannot be disposed. Although often illegal, marine disposal of garbage continues. Also continuing is the disposal of garbage from land into the oceans. This occurs through littering of beaches by tourists (Pruter, 1987), outfall from factories (Gregory, 1978), rivers (Pruter, 1987) and sewage (Ye & Andrady, 1991). Garbage entering the oceans may survive for considerable periods. This is especially true of some plastics, such as monofilament netting and polypropelene cordage, which may last over 50 years (Gregory, 1990a), though many plastics will survive for shorter periods (Gregory 1983; Dixon & Dixon, 1981). Glass objects may presumably also last considerable lengths of time. Much garbage also has positive buoyancy, so will drift around on the oceans (Ye & Andrady, 1991) until it disintegrates, sinks, washes ashore or is eaten by marine organisms. Ingestion of plastics by marine organisms is common and has been reported in over 50 species of birds (Fry, Fefer & Sileo, 1987; Gregory, 1990a), cetaceans, manatees (Laist, 1987) and turtles (Bjorndal, Bolton & Lageux, 1994). Ingestion of plastics may prove fatal if the gut becomes blocked (Laist, 1987; Bjorndal et al., 1994), or if toxic chemicals leach from the garbage (Merrell, 1980). Additionally, entanglement in debris (especially discarded fishing gear, plastic strapping bands, beer-can yokes, etc.) is a serious problem for many species of marine mammals, birds, turtles and fish (Laist, 1987). Upon washing ashore the hazard of garbage does not end. Beachgoers may face injury from broken glass or medical equipment (Dixon & Dixon, 1981), and terrestrial organisms may ingest garbage on the beaches (Merrell, 1980). It is difficult to assess the amount of garbage on the oceans directly (Dixon & Dixon, 1981), whereas it is not difficulty to assess the quantities of litter on beaches. Beach surveys provide valuable information on the amounts and types of garbage in the oceans. This is especially true of more remote beaches as these do not suffer from local land-based pollution, so the information gained can be used to assess garbage longevity. The Pitcairn Islands are amongst the most remote in the world (being over 4500 km from the nearest continental landmass), and of these, the most remote of the islands is Ducie Atoll (24°40?S, 124°47?W) which is 472 km away from the nearest inhabited island (Pitcairn, population c. 50), and is rarely visited by passing yachts (it has no fresh water or sheltered anchorage). Oeno Atoll (23°56?S, 130°45?W) is nearer to Pitcairn (some 160 km) and so is periodically visited by the islanders for their ‘holidays’ but, like Ducie, is rarely visited by passing yachts. Thus, anthropogenic garbage on these beaches is most unlikely to be locally produced, and most likely to have drifted considerable distances before being deposited on the beaches. In comparison, the litter
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found on many beaches in populated parts of the world is often of local origin. To illustrate this comparison, beach-litter surveys are presented here for Ducie, Oeno and a beach in south-west Ireland (Inch Strand, Dingle Peninsular, Co Kerry, Eire: GR 660980). METHODS
Ducie Atoll The survey was conducted on 28 and 29 March 1991. The seaward beach of the largest motu in the Atoll, Acadia Island, was surveyed as a continuous belt transect some 4000 m long (M. Brooke, personal communication) (see Spencer 1995, Fig. A4). Approximately one third of this beach faces the prevailing winds, whereas the remainder lies roughly parallel to the wind. Objects within a 2 m wide strip were noted. The beach on the seaward side of Acadia is steep, narrow and consists largely of coarse coral rubble. Thus small objects are often hidden between lumps of rubble and may be underrepresented in the sample. Oeno Atoll This survey was conducted by Dr Richard Preece and Sue Schubel in November 1991. An area (500 m×5 m) of beach on the sandy spit (see Spencer 1995, Fig. A3) was exhaustively searched to ensure all objects of anthropogenic origin within the area (approximately 2500 m2) were noted. The searched area was on the leeward side of the spit, in the centre of the lagoon, and consisted of banked coral sand. Inch Strand, Ireland A single belt transect was conducted along the upper shore on 25–26 September 1993. This transect was calculated to be 891 m (1100 paces at an average of 81 cm per pace). Objects within 2 m either side of my track were noted. Inch Strand is a depositional beach, facing into the Atlantic and the prevailing winds. The beach is backed by high (up to 30 m) dunes. Prior to the survey there had been strong onshore winds, which caused much drifting of sand up the beach. Thus, again, small items may be underrepresented in this sample, as they were more likely to be buried completely. RESULTS
The absolute amount of garbage in the three locations of Ducie, Oeno and Inch is frighteningly large (Table 1). On Ducie there were approximately 0.12 pieces of garbage m−2 beach surveyed, on Oeno, 0.35 pieces m−2 and on Inch Strand 0.22 m−2. Thus, in the remote South Pacific there are similar levels of garbage on the beaches to those found on a beach in populated and industrialized Europe. The proportions of garbage of different types is also remarkably similar between the islands in the Pitcairn Group and the beach in Ireland (Table
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TABLE 1. The major categories of marine litter on the three beaches surveyed. Single items, not fitting in any category, may be excluded from this table. The data from Ducie was originally published in Benton (1991). * indicates category included in statistical analysis (‘common rubbish’, where total found on all three beaches ×15 items). + indicates a single plastic bin-liner was also found containing an estimated 30 used nappies ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Ducie Oeno Inch Category n % n % n % ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — * Unidentified and misc. plastic 268 28 305 35 182 20 * Buoys (and bits) 179 19 67 8 28 3 * Glass bottles 171 18 148 17 54 6 * Bottle tops 74 8 76 9 55 6 * Plastic bottles 71 7 62 7 94 11 * Cord:rope 44 5 51 6 103 12 * Plastic pipe fragments 29 3 26 3 4 ³1 * Shoes 25 3 7 ³1 2 ³1 * Glass jars 18 2 — — 11 1 Crates (for food and drink) 14 1 — — 1 ³1 Aerosol cans 7 ³1 4 ³1 4 ³1 * Food tins:drink cans 7 ³1 7 ³1 17 2 * Light bulbs 6 ³1 31 4 1 ³1 * Fluorescent tubes 6 ³1 22 3 — — Cigarette lighters 3 ³1 5 ³1 3 ³1 Pen tops 2 ³1 3 ³1 — — Plastic strapping — — 16 2 21 2 * Cut wood — — 6 ³1 15 2 Bits of bucket — — 5 ³1 2 ³1 * Polythene bags — — — — 106 12 * Sweet:crisps wrappers — — — — 34 4 Disposable nappies — — — — 13+ 1 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Other items (total found) 27 (951) 37 (878) 44 (794) Density (items m−2) 0.12 0.35 0.22 0.24 1.76 0.89 Estimated items linear m−1 ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– —
1). To assess the similarity of the beaches, I ranked the 15 most common categories of rubbish (from Table 1) and calculated Spearman’s rank-order correlation between the three possible pairwise combinations of the three beaches: Ducie vs Oeno, rs 0.876, P ³ 0.001; Ducie vs Inch, rs 0.393, P × 0.1; Oeno vs Inch, rs 0.352, P × 0.2. Thus, the proportions of rubbish in the different categories are similar on Ducie and Oeno, but less so in Inch. However the low correlations between the Pacific and European beaches are caused by two points only: those for polythene bags and sweet:crisp wrappers. Removal of these categories from the analysis gives: Ducie vs Oeno, rs 0.82, P ³ 0.002; Ducie vs Inch, rs 0.73, P ³ 0.01; Oeno vs Inch, rs 0.68, P ³ 0.02. Therefore, leaving aside polythene bags, sweet wrappers and uncommon items, each beach is broadly similar in the rank-order of rubbish categories; rubbish common on one beach tends to be common on the others (e.g. pieces of plastic, glass bottles, etc), whereas rubbish rare on one beach also tends to be rare on the others (e.g. shoes, jars, tin cans, etc). To investigate this more exhaustively, the 15 common categories were analysed using a Chi-square contingency table to assess whether there were associations between beaches and litter types. As expected, the overall Chisquare is highly significant (Chi-square 710, df 28, P ³ 0.0001). However,
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TABLE 2. Some oddities from the three beaches ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Ducie Oeno Inch ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — tinned meat pie, intact, but leaking bicycle pedal veterinary examining glove (elbow length) dolls’ heads (male+female) toy car used syringes (5) toy aeroplane toy aeroplane window frame football baby’s dummy measuring cylinder plastic skittle screwdriver car seat asthma inhaler candle wax used hypodermic needle tea strainer tea strainer suitcase handle letter in wine bottle* shotgun cartridge lego brick ‘Watney’s’ beer barrel* egg carton car foot-mat car foot-mat toy soldiers (2) plastic hair curlers ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — * Found on Ducie, but not on the reported transect.
what is of interest are the component chi-squares for each category as these illustrate which beaches differ from the others. If all the beaches were identical, then rubbish would distribute itself similarly between beaches. Thus, the analysis highlights where rubbish in each category is more or less common than expected. Polythene bags are much more common than expected at Inch; buoys are much more common on Ducie, slightly less common on Oeno and much less common in Inch; sweet wrappers are much more common at Inch; string:cord and rope are much more common at Inch; bulbs and fluorescent tubes are significantly more common on Oeno compared with the other two; the reverse is true for glass jars and plastic fragments; glass bottles are significantly rarer in Inch than the Pacific, whereas the reverse is true for plastic bottles; shoes are more common on Ducie; tin cans are more common in Inch, as is cut wood; bottle tops are equally common on all three beaches. Thus, as well as similarities, there are differences between the beaches in the proportions of rubbish in the common categories. However, it is not solely the amount of rubbish that is of some interest, but also its diversity. In this respect all three beaches have a similar diversity (Table 2); it is just that, especially on the remote Pacific beaches, this diversity is most unexpected for someone naive of the literature (e.g. Pruter, 1987; Gregory, 1990b). Given that most garbage must drift considerable distances to land on Ducie and Oeno, it is remarkable that such items as toys, footballs, tea strainers, car foot mats and so on survive to drift ashore. The country of origin was determined for a sub-sample of 130 glass bottles on Ducie (Table 3). The single most common country of origin was Japan and the most common type of bottle once contained whisky (especially Suntory Whisky from Japan). The diverse origins of these bottles makes it unlikely that they drifted from their countries of origin, but were most likely dumped at sea. However, the commonness of pieces of pumice and tree-fern logs on the Pitcairn Islands, which are both likely to originate in South America, testifies to the possibility of long-distance oceanic travel (see Jockiel, 1989). Long distance is however relatively unlikely for any given piece of garbage, with many items sinking, degrading, being ingested or washing ashore for each piece remaining afloat for great lengths of time. On the whole of Inch Strand I encountered only
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TABLE 3. Origins of a sample of 130 glass bottles from beach on Acadia Island, Ducie. The diversity implies that many were disposed of from boats, rather than drifting from source countries –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Country n Comments –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– — Japan 41 mainly Suntory whisky Unidentified 35 4 beer, others mainly wine Scotland 11 all whisky UK 9 whiskys + Harvey’s sherry USA 8 mainly Schweppes soft drinks ? South America 4 labelled in Spanish:Portuguese Germany 3 soft drinks New Zealand 3 France 2 brandy Holland 2 Russia 2 1 vodka Venezuela 2 Italy 1 wine Spain 1 Portugal 1 Argentina 1 –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– —
12 pieces of garbage likely to be long-distance drifters (as assessed by epifaunal community as well as the country of origin): Spain:Portugal 6, France:Belgium 3, Morocco 1, US 2). If I generalize the estimate of garbage density (from the surveyed 891 m) to the whole of Inch Strand (5.4 km), then only about 1 item in a 1000 to land on the beach has drifted long distance. As items have to drift long-distances to wash ashore in the Pitcairn Islands, then to account for the presence of so much rubbish on the beaches, perhaps 1000 items thus have to be thrown into the ocean for every one encountered on the beach. DISCUSSION
The major, and somewhat alarming, conclusion from this study is that beaches in the remote South Pacific have a comparable amount of garbage to a beach in the industrialized western world. In 1993, 1238 volunteers collected rubbish on 121 beaches around the UK, as part of ‘Beachwatch 93’. These collections cleaned entire widths of shore, whereas the Ducie and Inch surveys reported here only noted rubbish in a narrow band along the strand line, and so surely underestimate the total number of items per linear metre of beach. However, the median items per linear metre for beaches in the UK is 0.52 (range 0.137–9.83) (data from McGilvray, 1994). In comparison, the data presented here represent estimates of 0.24 (Ducie), 0.89 (Inch) and 1.76 (Oeno). So, although the beaches in Ducie and Oeno are rarely visited by humans, and are thousands of kilometers from the nearest industrial centres they are as dirty as other areas of the world. Sadly, it is well known that many remote Pacific islands are strewn with litter washed ashore (Gregory, 1990b), and the same applies to other remote locations in the world (Merrell, 1980; Gregory, 1990a). It is also unfortunate to note that during a visit to Ducie at the end of July 1992, members of the Expedition
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found large amounts of tar on the beaches, presumably caused by a tanker illegally washing out its tanks in mid-ocean (M. Brooke, personal communication). The pollution on beaches, as well as being unsightly, also poses a threat to wildlife. Imber, Jolly & Brooke (1995) found that petrels on Ducie had sometimes ingested plastics, and the green turtles on Henderson (Brooke, 1995) may also be at risk (Bjorndal et al., 1994). However, this flotsam may also, more rarely be of use to local wildlife. On Henderson, land hermit crabs (Cenobita sp.), were occasionally found to select items of garbage (such as the lids of aerosol cans, heels of shoes etc.) as shelters rather than the more traditional shells. Additionally, flotsam floating in the oceans may serve as rafts allowing the dispersal of a wide range or organisms (e.g. Jockiel, 1989); many items encountered on the beaches of Henderson and Ducie had often extensive epifaunal communities of barnacles, bryozoans and corals. Although broadly similar in garbage densities, the beaches of the Pacific differ from the beach in Ireland in subtle ways. In Ireland, there was an excess of locally-produced non-durable material (such as sweet wrappers, plastic bags, tin cans, disposable nappies etc). Conversely, in the Pacific there was an excess of the more durable items (especially glass bottles and buoys). The more easily degraded litter, found in Ireland, presumably does not survive sufficient periods to drift to the more remote locations; and much of the useful, durable, flotsam (e.g. intact buoys) found in the Pacific may be removed by beachcombers in Ireland and other populated parts of the world (indeed, the Expedition made considerable use of items of flotsam, using buoys for constructing moorings, wood and plastic for furniture, and a plastic funnel to make equipment for extracting insects from soil). However, the presence of plastic bottles of considerable age on Inch Strand (as denoted by the chalky, friable appearance of the plastic) attests to some considerable longevity of some items. It should be noted that the differences between the two beaches in the Pacific may be as great as the differences between the Irish and Pacific beaches. Just as Inch has an excess of flimsy plastics, Oeno has an excess of light bulbs and fluorescent tubes, and Ducie has an excess of jars, buoys and shoes. Thus each beach is unique, and the differences between them are perhaps more subtle than may have been expected from their locations in the remote Pacific and polluted Europe. The overall similarity of garbage between the three beaches perhaps testifies to similar sources. Much of the garbage, perhaps most of it, undoubtedly comes from marine dumping. Ships sailing between Australia:New Zealand and Panama may pass quite close to the Pitcairn Islands, and many vessels sail the North Atlantic. This ship-produced garbage is supplemented in Ireland by the garbage of beachgoers and local people (many domestic refuse sacks appear to be dumped over cliffs directly into the sea). The beaches of the remote Pacific, rarely visited by humans, carry as much garbage as beaches in more industrialized areas in Europe (Ireland: this study: UK: McGilvray, 1994; Mediterranean: Gabrielides et al., 1991). Thus, even though these areas are not inhabited they suffer the long-distance pollution from the inhabitants of other places. The animals on these remote islands may have little chance of encountering humans, but every chance of encountering the life-threatening waste we generate.
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I would like to thank Richard Preece and Sue Schubel for doing a rubbish survey on Oeno, the University of East Anglia for having an ecology fieldcourse in Inch, Peter Jones and Mike Brooke who originally suggested my garbage notes might be worth publishing, and Murray Gregory for constructive comments on an earlier version. My visit to the islands as part of the Sir Peter Scott Commemorative Expedition was generously supported by the following major sponsors: The Royal Society, International Council for Bird Preservation, British Ornithologists’ Union, J. A. Shirley, Foreign & Commonwealth Office UK, UNESCO; all other sponsors are acknowledged in the expedition report of 1992. This is paper 52 of the Sir Peter Scott Commemorative Expedition to the Pitcairn Islands. REFERENCES Benton TG. 1991. Oceans of garbage. Nature 352: 113. Bjorndal KA, Bolten AB, Lageux, CJ. 1994. Ingestion of marine debris by juvenile sea turtles in coastal Florida habitats. Marine Pollution Bulletin 28: 154–158. Brooke MdeL. 1995. Seasonality and numbers of green turtles Chelonia mydas nesting on the Pitcairn Islands. Biological Journal of the Linnean Society 56: 325–327 Dixon TR, Dixon TJ. 1981. Marine litter surveillance. Marine Pollution Bulletin 12: 289–295. Fry DM, Fefer SI, Sileo L. 1987. Ingestion of plastic debris by Laysan albatrosses and wedge-tailed shearwaters in the Hawaiian Islands. Marine Pollution Bulletin 18: 339–343. Gabrielides GP, Golik A, Loizides L, Marino MG, Bingel F, Torregrossa MV. 1991. Man-made garbage pollution on the Meditterranean coastline. Marine Pollution Bulletin 23: 437–441. Gregory MR. 1978. Accumulation and distribution of virgin plastic granules on New Zealand beaches. New Zealand Journal of Marine and Freshwater Research 12: 399–414. Gregory MR. 1983. Virgin plastic granules on some beaches of eastern Canada and Bermuda. Marine Environmental Research 10: 73–92. Gregory MR. 1990a. Environmental and pollution aspects. In: Glasby, EP, ed. Antarctic sector of the Pacific. Elsevier Oceanography Series 51: Amsterdam: Elsevier. 291–324. Gregory MR. 1990b. Plastics: accumulation, distribution, and environmental effects of meso-, macroand megalitter in surface waters and on shores of the southwest Pacific. In: Shomura RS, Godfrey ML, eds. Proceedings of the Second International Conference on Marine Debris, 2–7 April 1989, Honolulu Hawaii. US Department of Commerce, NOAA Technical Memo: NMFS, NOAA-TM-NMFS-SWFSC154. Horsman PV. 1982. The amount of garbage pollution from merchant ships. Marine Pollution Bulletin 13: 167–169. Imber M, Jolly JN, Brooke MdeL. 1995. Food of three sympatric gadfly petrels (Pterodroma spp.) breeding on the Pitcairn Islands. Biological Journal of the Linnean Society 56: 233–240. Jockiel PL. 1989. Rafting of reef corals and other organisms of Kwajalein Atoll. Marine Biology 101: 483–493. Laist DW. 1987. Overview of the biological effects of lost and discarded plastic debris in the marine environment. Marine Pollution Bulletin 18: 319–326. McGilvray F. 1994. Beachwatch 1993. Ross-on-Wye, Herefordshire: Marine Conservation Society:Reader’s Digest. Merrel TR. 1980. Accumulation of plastic litter on beaches of Amchitka Island, Alaska. Marine Environmental Research 3: 171–184. Pruter AT. 1987. Sources, quantities and distribution of persistent plastics in the marine environment. Marine Pollution Bulletin 18: 305–310. Spencer T. 1995. The Pitcairn Islands, South Pacific Ocean: plate tectonic and climatic contexts. Biological Journal of the Linnean Society 56: 13–42. Ye S, Andrady AL. 1991. Fouling of floating plastic debris under Biscayne Bay exposure conditions. Marine Pollution Bulletin 23: 608–613.