27. Chagomelana J.E. (1989). Drought monitoring and impact activities in
Malawi. Paper presented
the Drought Preparedness Seminar, Gaborone,
28. Walker R.S. (1988). Long-term dala series from South African Grasslands.
In Proc. Conference on Long-Term Data Series Relating to southern
Africa's Renewable Natural Resources, edit. I.A.W. Macdonald and R.J.M.
Crawford. South African National Scientific Programmes Report No. 157,
253 -267, Pretoria.
29. Weisser P.J., Backer A.P. and Van
(1988). Aerial photographs as a
long-term data source for vegetation studies.
Long-Term Data Series Relating to southern Africa's Renewable Natural
Resources, edit. I.A.W. Macdonald and R.J.M. Crawford. South African
National Scientific Programmes Report No. 157. 253 -267. Pretoria.
30. Van Zyl J.H. and Viljoen M.F. (1986).
sosio-ekonomiese gevolge van
besproeiingsboerderye, mynbou, elektrisiteitsvoor-
siening en die sentrale owerheid. Water Research Commission, Report No.
31. Schlemmer L., Stewart G. and Whittles J. (1989). The socio-economic
local authorities, selected industrial and
commercial establishments and other private agencies. Water Research
Commission, Report No. 168/I/89,Pretoria.
32. Van Zyl J., Van der Vyver A. and Groenewald J.A. (1987). The influence
drought and general economic effects on agriculture: a macro-analysis.
33. Van Zyl
and Nel H.J.G. (1988).
the maize industry in the
South African economy. Agrekon 21,
34. Vierich H. (1980). The implications
drought for non-village populations
living in remote areas in the Sandveld. In Drought in Rural Botswana:
Governmental Policy, edit. H. Vierich and C.
Sheppard. Rural Sociology Unit, Ministry
35. Vierich H. and Sheppard C. (1980). Drought in Rural Botswana: Socio-
Government Policy. Rural Sociology Unit, Ministry
36. Muller N.D. (1984). Aspects
drought and water
in the Transkei. Proc. Secoftd Carnegie Inquiry into Poverty
Development in South Africa. Carnegie Foundation, Cape Town, 1 - 27.
37. Freeman C. (1984). Drought and agricultural decline
South African Review II. Ravan Press, Johannesburg,
38. Freeman C. (1988). The changing impact
drought on rural Tswana
society. MA dissertation, University
the Witwatersrand, Johannesburg.
Water Affairs (1986). Management
the Water Resources
South Africa. Government Printer, Pretoria.
Plastic and other artefacts
African beaches: temporal
abundance and composition
Plastic debris has rapidly become one
lhe most abundant
marine pollutants, wilh economic as well
50 Soulh African beaches in 1984 and
again in 1989 show lhat lhe densities
all types of plastic
objects have increased significantly. The greatest increase has
been in packaging and other disposable items, lhe vast majority
of which are manufactured locally. Urgent steps are needed
now to stem lhe tide
plastic debris at sea off Soulh Africa.
Man-made articles enter the sea from ships and from a dif-
land-based sources. Most artefacts found
plastics, a group
artificial polymers de-
. veloped during the last fifty years lhat are virtually immune
biodegradation. As a result
long lifespans, plastics lhat float
in sea-water disperse far from source areas, and are the most
abundant contarninents of oceanic surface waters. Off Soulh
Africa, the mean density
plastic is 3600 particles km-2,
intermediate between low densities typical of polar regions and
high densities typical
coastal waters abutting industrial
Floating plastic objects and other artefacts have three main
impacts on the marine environment:
they are ingested by
and entangle many marine animals;
they increase the
substratum available for epiphytic organisms; and
when stranded, they reduce the aesthetic appeal and tourism
beaches. These impacts can have serious ecological
South African Journal
and economic consequences, and recently have been the focus
international concem.2.3 It is often assumed that the density
are few actual measures
of temporal changes in lhe abundance and composition
facts. Such measures are needed to assess lhe dynamics of
marine debris and to determine lhe efficacy
reduce lhe amount of marine debris. We present pre-
trends in plastic abundance off South
Africa, estimated from sampling bolh micro- and macro-plastic
particles stranded at a range
beaches over a five-year period.
Monitoring lhe density
sea is time-consuming
and costly ,1 whereas marine debris stranded on beaches is
readily surveyed. Assuming that within-beach variation in
artefact density (both spatially and
a short temporal scale) is
not too great, beach surveys provide an effective method for
assessing temporal changes. We sampled artefacts
beaches in lhe Cape Province, Soulh Africa, between Saldanha
Bay and the Kei river mouth during the austral winters of 1984
and 1989. Sampling sites were selected from relatively uniform
areas in lhe centre
beaches, and similar sites were sampled
each beach during 1984 and 1989. Beaches were categorized
urban (within towns or at beach resorts; n = 27) or rural
(distant from large settlements or resorts; n = 25).
Sampling was performed
two levels: micro-artefacts
( < 20 mm diameter) were collected from a 0.5-m-wide tran-
sect running up the beach by sieving lhe top 50 mm
through a 2-mm mesh sieve (n =
beaches); and macro-arte-
20 mm) were collected from 50-m stretches
(n = 51) and were identified
addition, pumice was collected along with
micro-artefacts in 1984.
Micro-plastics were grouped into three categories: virgin
industrial pellets that form the feedstock for the plastics
industry, expanded polystyrene, and fragments
articles (e.g. pieces
bottles and bags, rope fibres, etc.).
Macro-plastics were grouped into four categories: packaging
and other disposable items (e.g. bags, bottles, straps, etc.),
fishing equipment (nets, line, floats, etc.), non-disposable user
objects (shoes, gloves, etc.), and unidentified pieces.
More than 40 000 artefacts were sampled during the two
surveys. Plastics comprised more than 90% of artefacts on
South African beaches, making up 88%
macro- and 98% of
micro-artefacts. Non-plastic macro-artefacts were, in
importance, made from wood, glass,
metal, paper, clolh and wax products. Most non-plastic micro-
artefacts were cigarette stubs.
There were consistent inter-beach differences in the
plastics, both between lhe various types of
plastics, and between lhe 1984 and 1989 surveys (Fig.
Significant correlations between lhe numbers
bolh microplastics (r, = 0.61; n = 51; P < 0.001) and macro-
plastics (r, = 0.34; n = 50; P < 0.05), suggest that inshore
currents ralher than local sources are responsible
lhe inter-beach variation in plastic abundance, because pumice
on beaches derives from offshore sources and is dispersed by
lhe sea. However, the relatively weak correlation between
pumice and macro-plastics indicates lhat local sources play a
larger role in the distribution
There were significant increases in lhe abundance
plastic types between 1984 and 1989 (Figs 2 and
micro-plastic particles increased from 491 m-1 of
1984 to 678 m-1 in 1989 (Fig.
Suid-Afrikaanse Tydskrifvir Wetenskap Vol. 86
Total numbers 1984
. . .
E 100 .
10 . .
Total numbers 1984
Correlations between counts of plastics on beaches in
1984 and 1989, showing consistent inter-beach differences in
the density of both micro- and macro-plastics.
sample test; T = 262.5; n = 51; P < 0.001). Most micro-
plastics were virgin industrial pellets, which were proportion-
ately less abundant in 1989 (68%) than in 1984 (80%),
although there was a significant increase in absolute abundance
between 1984 and 1989 (mean density up by 17%; T = 368;
n = 51; P < 0.01). The increase in the abundance
micro-plastics was much greater, with a 54% increase in
expanded polystyreny (T = 244; n = 42; P < 0.01) and a
145% increase in fragments
other user items (T = 127; n =
51; p < 0.001).
macroplastic objects increased from an
beach in 1984 to 2.99
1 in 1989 (Fig.
T = 57.5; n = 51; P < 0.001). Packaging and other dispos-
able products accounted for 69%
in 1989 (up from 65% in 1984), with an absolute increase
175% (T = 61; n = 51; P < 0.001). Fishing
equipment, which comprised most of the remaining macro-
plastic objects, also increased in abundance between 1984 and
1989 (mean density up
117%; T =
n = 49; P <
0.001), but to a lesser extent than packaging and disposable
origin could be determined for 1300 (17%)
macro-plastic objects sampled in 1989; 96% were produced in
South Africa. The proportion
locally produced articles was
urban (98%) than on rural beaches
(92%; x2 = 25.10; d.f. =
p < 0.001). The density
aging and disposable items was 65% greater
urban than on
rural beaches, and the proportion
packaging was larger on
urban (71%) than
rural beaches (50%; Mann-Whitney
= 433; Z = 2.03; P < 0.05 for 1989 data).
The results demonstrate that the abundance of plastic objects
on South African beaches has increased between 1984 and
is not immediately clear whether this result reflects an
increase in the amount
plastic entering the sea over the last
that the long life-spans
plastic articles in the
environment has lead to a greater accumulated amount
plastics on beaches. For some relatively short-lived objects
bags and wrappers, the marked increase in abundance
:2 Pellets Pieces
Changes in the mean abundance of
South Mrican beaches between
and the preponderance
recently introduced packaging
designs suggests that there has been a large increase in the
plastic pollution. However, for long-lived objects
such as virgin industrial pellets, which showed the smallest
absolute increase in abundance, there may actually have been a
decrease in the amount entering the sea. More information is
needed on the life-spans
plastics (at sea,
and exposed and buried on beaches) and on beach-sea inter-
plastics before the dynamics
on beaches can be resolved.
However, given the strong marine influence on the distribu-
tion of plastics on beaches, it is safe
assume that the
increase in beach pollution reflects an increase in the density
sea off South Africa. There is evidence from a wide
range of organisms that plastic debris has a deleterious effect
on the marine environment off South Africa,4 where among the
seabirds have been
recorded.5 Because the impact of plastic pollution is a function
its density at sea, concerted action is necessary
Much plastic debris is dumped from ships, but international
legislation (Annex V
the International Convention for the
Pollution from Ships, to which South Africa has
accede) recently has outlawed the dumping of plas-
tics at sea for more than half the world's shipping.6 This mea-
sure, coupled with the positive attitude expressed
merchant fleets, should greatly reduce pollution from ships.
More difficult to control is litter from the flotilla
craft and small fishing boats that operate around the South
African coast. Dumping from these vessels also is banned
under the new legislation, but enforcement is all but impossi-
small boat users
However, a large proportion
plastic pollution also derives
from local, land-based sources: hence the predominance of
Changes in the mean abundance of four categories of
South African beaches between
products and the differences
between the composition
litter on urban and rural beaches.
the public is needed to change complacent atti-
tudes towards littering, but current concerns about the efficacy
of education campaigns7 also necessitate a reduction in the
plastic being used in disposable applications.8 Con-
sequently, a multifaceted approach incorporating education,
product substitution, retycling and legislation is required to
reduce the flow
plastics and other persistent synthetic
objects into the marine environment.
We thank the Plastics Federation of South Africa for sponsoring the
1989 survey. Support for the 1984 survey was received from CSIR,
South African National Committee for Oceanographic Research
and the South African Scientific Committee for Antarctic Research.
Access to the Overberg Testing Range is gratefully acknowledged.
P.G. RYAN and C.L. MOLONEY
FitzPatricklnstitute and Marine Biology
Research Institute, Univ1rsity
Rondebosch, 7700 Soutli Africa.
Ryan P.G. (1988). The characteristics and distribution
plastic particles at
the sea-surface off the southwestern Cape province, South Africa Mar.
Environ. Res. 25,
Shomura R.S. and Yoshida H.O. (Eds) (1985). Proceedings
Workshop on the Fate and Impact
Marine Debris. U.S. Dept Commerce,
NOAA Tech. Memo., NMFS 54, 1 - 580.
Wolfe D.A. (Ed.) (1987). Plastics
the sea. Mar. Polful. Bull. 18, 303 -
Ryan P.G. (in press). The marine debris problem 'off southern Africa: types
debris, their environmental effects, and control measures. Proceedings
the Second International Conference on Marine Debris, Honolulu, April
1989, ediL R.S. Shomura and M.L. Godfrey. U.S. Department
5. Ryan P.G. (1987). The incidence and characteristics
ingested by seabirds. Mar. Environ. Res. 23,
(in press). Legal strategies for discouraging the dumping
into the marine environmenL Proceedings
Conference on Marine Debris, Honolulu, April 1989, edit.
and M.L. Godfrey. U.S. Department
Laska S. (in press). Designing effective educational campaigns: the
the Second /11/ernationa/
Marine Debris, Honolulu, April 1989, edit. R.S. Shomura
and M.L. Godfrey. U.S. Department
Wirka J. (1988). Wrapped in plastic.•: the environmental case for reducing
plastics packaging. Environmental Action Foundation, Washinglon,D.C.
20 000 years: isotopic evidence from
2C ratio analysis
grazing bovids provides a means for
determining shifts in the distribution
Since the distribution
these grasses is essentially
constrained by temperatures during the growing season
grasses favour cool growing seasons, C4 grasses warm1
depending on the locality, the distribution would change
rainfall were to change. Thus predictions
shifts in summer and winter rainfall zones in southern Africa
during the last 25 000 years,2 based on a recent model for the
present climate,3 may be tested.
this preliminary study
grazers from Equus Cave in the northern Cape, enamel apatite
is used as an alternative sample material4•5 to the usual bone
collagen, which is poorly preserved at the site. The results
show that there were periods in the last 20 000 years with
relatively higher proportions
grasses always dominated. Therefore, the data do not
support a complete change to winter
in this area.
Recently, models developed for the contemporary South
have been extended to provide explanations
for climatic shifts in the late Quaternary? The model predicts a
substantial northeasterly shift
the winter rainfall belt into the
Transvaal between 25 000 and
000 years ago, with the ex-
the period 20-18 000 BP.2 (The Last Glacial
Maximum is generally held to have ·been about
This prediction may be tested by stable carbon isotope analysis
of grazers from suitable archaeological sites, according
following rationale. The present distribution
photosynthetic pathways is sharply
patterned in South Africa; in general, the latter predominate in
the summer rainfall zone, while the former predominate in the
winter rainfall (southwestern Cape) and high Drak:ensberg
regions.1 This pattern has been ascribed to temperature
constraints during the growing season - C4 grasses are
favoured where daily maximum temperatures in the rainy
season remain above 25°C, and minimum temperatures above
1 These constraints are met in most
the summer rainfall
zones. Below a mean daily maximum of 25°C in the growth
grasses become more successful (i.e. winter rainfall
zones and cool high altitude areas).
the uniform rainfall belt
between the summer and winter rainfall zones, the distribution
the two types seems to be related to microclimatic
Major shifts in the rainfall belts, such as those predicted
the last 25
years,2 would also affect the distribution
C4 grasses. Since the
the two groups are
distinct, and herbivore tissues reflect the isotopic ratios of the
2C ratios from bones or teeth of grazers
from archaeological sites will reveal shifts in the proportion of
grasses in the area.
practice, over most of the
country, this also reflects whether rain falls predominantly in
the winter or summer, subject to the important constraint that
temperatures do not fall below 25°C in the growing season in
the summer rainfall zone.
only study using these principles to address
palaeoenvironmental questions in southern Africa used a
grazer collagen specimens from a site in
Lesotho (Melik:ane Cave) and in Namibia (Apollo 11).10 Re-
sults for the latter site led
the conclusion that the winter
rainfall zone had not extended much further than its present
range; and for the former site, that there had been an expansion
grasses due to a decrease in temperature
during the Last Glacial period.10
this study, predictions from the climatic
approximately the last
000 years are compared with
results obtained from a stratigraphic sequence of
grazers from Equus Cave. The cave is situated on the Ghaap
escarpment near Taung in the northern Cape. The site, exca-
vated in 1978 and 1982,
was a prehistoric brown hyena den,
rather than a human occupation site.
It yielded one of the
largest Pleistocene faunal assemblages in the world,
brown hyena (Hyena brunnea) coprolites, which have been
used to establish a palynological sequence,
and a few human
fragments.14 Dating has been a problem owing to lack of
suitable material. Three radiocarbon dates are available: 2390
BP (Pta-2452), 7480 ± 80 BP (Pta-2495) from layer
and 16300 ± 160
(Pta-4409) from the top of layer
the site may thus be considered to span about 20 000 years.
At present, the climate is semi-arid, less than
5 and grass cover is almost entirely C4•1
According to the climate model.Z this area would have fallen
within the expanded winter rainfall belt during the period
15-17 000 BP. Some palaeoclimatic data have been obtained.
Faunal analysi;2 suggests that conditions were grassier, cooler
and perhaps moister in the periods
2A and 2B.
The pollen sequence
indicates that temperatures were not
lower during the coolest part
Pleistocene, although a 5-6°C lowering