Personal tools
Home » Members » broitman » EBM Scales reading group » EBM Scales pdfs » Sandy shore ecosystems and the threats facing them: some predictions for the year 2025
Document Actions

Sandy shore ecosystems and the threats facing them: some predictions for the year 2025

Environmental Conservation 29 (1): 62–77 © 2002 Foundation for Environmental Conservation           DOI:10.1017/S037689290200005X

Sandy shore ecosystems and the threats facing them: some predictions for
the year 2025
Zoology Department, University of Cape Town, South Africa 7701 and 2College of Science, Sultan Qaboos University, Oman
Date submitted: 25 April 2001 Date accepted: 28 November 2001

SUMMARY                                   nourishment is likely to become more widely prac-
                                       tised. However, the continuing hardening of surfaces
Pollution, mining, disruption of sand transport and
                                       in and above the dunes is bound to be damaging.
tourism development widely affect sandy shores, and
                                       Human pressures in many underdeveloped countries
these systems may be subject to increased erosion in
                                       show no signs of being mitigated by conservation
future, yet there have been few attempts to review
                                       measures; it is likely that their sandy shores will
them. The present review focuses largely on ocean
                                       continue to deteriorate during the first quarter of this
sandy beaches, providing an introduction to much of
                                       century. A long-term trend that cannot be ignored is
the relevant literature, and predicting possible states
                                       the excessive amount of nitrogen entering the sea,
of the system by 2025. Sandy shores are dynamic harsh
                                       particularly affecting beaches in estuaries and shel-
environments, the action of waves and tides largely
                                       tered lagoons. The data presently available and the
determining species diversity, biomass and
                                       uncertainty of a number of predictions do not permit
community structure. There is an interchange of sand,
                                       of quantitative assessment or modelling of the state of
biological matter and other materials between dunes,
                                       the world’s sandy shores by the year 2025, but some
intertidal beaches and surf zones. Storms and associ-
                                       tentative, qualitative predictions are offered.
ated erosion present the most substantial universal
hazard to the fauna. Human-related perturbations               Keywords: sandy shores, ecology, climate change, human
vary from beach to beach; however, structures or               interference
activities that impede natural sand transport or alter
the sand budget commonly lead to severe erosion,
often of a permanent nature. Many beaches also suffer
intermittent or chronic pollution, and direct human             Sand or mixed sand and rock make up some 75% of the
interference includes off-road vehicles, mining, tram-            world’s ice-free coastlines (Brown 2001). An exposed sandy
pling, bait collecting, beach cleaning and ecotourism.            shore consists of coupled surf zone, beach and dune systems
These interferences typically have a negative impact             (Short & Hesp 1982), which together constitute a littoral
on the system. Identified long-term trends include              active zone of sand transport. On open coasts subject to
chronic beach erosion, often largely due to natural             oceanic swell, the depth of sediment transport may be
causes, as well as increased ultraviolet (UV) radiation           20 m and extend well beyond the surf zone, while aeolian
and changes related to global warming. It is not               transport of sand extends landwards to the fully vegetated
expected that predicted temperature changes will               dunes. The sandy shore, from the perspective of sand trans-
have dramatic effects on the world’s beaches by 2025,            port and coupled morphodynamic systems, includes marine
but the expected rise in sea level, if coupled with an            and terrestrial components, with the intertidal beach in
increase in the frequency and/or intensity of storms,            between. High energy beaches, receiving strong winds and
as predicted for some regions, is likely to lead to esca-          waves, usually have wide surf zones and, because of consider-
lating erosion and consequent loss of habitat. It is             able aeolian sand transport off the subaerial beach, are often
suggested that increased UV radiation is unlikely to             backed by large dune systems, such as transgressive dune
have significant effects. Increases in coastal human             sheets. Under sheltered conditions, by contrast, the littoral
populations and tourism, thus increasing pressure on             active zone is narrower, with a smaller surf zone and, because
the shore, while serious, may be largely offset in devel-          of the narrower beach and limited sand transport, small fore-
oped and developing countries by better management              dunes (Short & Hesp 1982). It is beyond the scope of this
resulting from greater understanding of the factors             paper to give full treatment to all three of the components
governing sandy-shore systems and better communi-              making up the system; this review therefore focuses on the
cation with beach managers and developers. Beach               subaerial beach but also touches on surf and dune systems
                                       where relevant. Indeed, as foredunes are in many respects the
                                       most sensitive part of the littoral active zone, threats to the
* Correspondence:  Professor     Alexander   Brown   e-mail:
                                       dune/beach interface deserve particular attention.
                                                   Sandy shores in 2025    63

  The present state of the world’s sandy shores is extremely   over 600 species (Brown 2001). Virtually all animal phyla are
variable. Some, in remote areas, are virtually pristine, with   represented. Bacteria and Protista live between the grains
low human population levels and yet to be discovered by      often in large numbers, but have for the most part been
tourists. Others, in industrial or overpopulated urban areas,   poorly quantified.
are seriously degraded due to chronic pollution and/or the      Intertidal sandy substrata range from sheltered sand flats,
hardening of surfaces, destruction of dunes and the        and sand in estuaries and sheltered lagoons to ocean beaches,
construction of sea walls. Between these extremes is a whole    which may face waves several metres in height even in calm
range of sandy shores suffering impacts from a wide variety    weather. The interaction of waves and tides with the available
of causes.                             sediment results in a series of morphological beach types. For
  This review attempts to address the chief threats to sandy   wave-dominated beaches the extremes are represented by the
coastlines and their faunas around the world, and to exposed    dissipative condition (where the wave energy is largely dissi-
beaches in particular, in the light of global climate change and  pated in a broad surf zone before reaching the intertidal sand,
increasing human pressures. It considers, as far as feasible, a  resulting in a gentle beach slope and non-turbulent swash)
time frame of some 25 years. At a time when global change is    and reflective beaches (where there is no true surf zone and
recognized by most authorities and when the human popu-      waves break on the beach face, much of their energy being
lation, concentrated on the coast, exceeds 6 billion, it is    reflected back towards the sea) (Short 1993a,b). Reflective
timely to take stock of the status of these important and sensi-  beaches have a more pronounced slope and larger particles
tive ecosystems and to assess how they may respond to these    than dissipative beaches and the swash tends to be turbulent.
threats within the next generation.                Paradoxically, high-energy beaches (i.e. those facing high
                                  breakers) tend to be flat and dissipative, while low-energy
                                  beaches are typically steep and reflective (Brown &
Features of sandy shores
                                  McLachlan 1990).
Sandy shores are dynamic environments with unstable          Wave-dominated beaches are found where waves are high
substrata, presenting hostile conditions to the biota. They    relative to tide range. This relationship may be formulated by
display a considerable range of physical conditions,        the relative tide range (RTR) (Masselink & Short 1993):
community structures and ecosystem functioning. They
                                            RTR   TR / Hb
consist of accumulations of particles deposited by waves, the                                  (1)
particles having diameters of 50–2000 m (0.05–2 mm).
                                  where TR    the range of spring tides and Hb
The particles originate chiefly from inland erosion and are                                 average
transported to sea via rivers; erosion of cliffs and rocky     breaker height. If the value of RTR is less than 3, the beach
shores may add to the sediment available (Bird 1985). The     is wave-dominated, if greater than 15 it is tide-dominated. If
particles generally consist of either quartz or silica, but    RTR is between 3 and 15, the beach is said to be tide-modi-
may also include heavy minerals, volcanic basalt and        fied. Tide-dominated sands all display low breaker height
feldspar. In addition, beaches commonly receive particles     (< 1 m) and are morphologically intermediate between ultra-
from marine biogenic sources, including shell fragments,      dissipative beaches and sand flats (Short 1996). If the tide
pieces of skeleton and sponge spicules (Brown &          range is small (2.0 m or less), tidal effects on beach
McLachlan 1990).                          morphology are minimized, but as tidal range increases, so
  The physical features of beaches reflect the interaction of   the location of the shoreline displays increasing mobility with
wave height, wavelength and direction with the tidal regime    tidal rise and fall. As a result, a given level of the intertidal
and the sediment that is available (Short 1993a,b). The      beach may be exposed to shoaling, surf and swash at different
resulting physical state of the beach, including slope, particle  states of the tide.
size distribution and swash climate, in turn determines        Wright and Short (1984) employed the dimensionless fall
                                  velocity (Gourlay 1968; Gibbs et al. 1971), commonly known
community structure, zonation and ecosystem functioning.
Water movements and their interaction with the sediment      as Dean’s Parameter, , to characterize wave-dominated
thus constitute the overriding factors to which virtually all   beaches:
sandy-beach phenomena are related.
  Obvious features of ocean sandy beaches include the                                     (2)
absence of attached macrophytes intertidally and the
                                  where Hb average breaker height (m), Ws sediment fall
apparent paucity of the fauna. Over 20 species of macrofauna
                                  velocity (m s 1) and T wave period (s). This formula has
may actually be resident, often in large numbers, but they are
mainly cryptic and typically emerge from the sand only at     been used extensively to quantify beach types ranging from
night, if at all (Brown 1983). As the tide rises, other macro-   fully dissipative through intermediate conditions to fully
faunal species commonly invade the intertidal beach from the    reflective. There are strong correlations between Dean’s
surf zone. However, the majority of intertidal sandy-beach     Parameter and macrofaunal species richness and abundance
                                             2.1 – 0.6, r2
animals are tiny and live between the sand grains; in contrast   (Fig. 1a: No. spp.            0.89; Fig. 1b: Log
                                  (n 1) 0.5 – 0.69, r2 0.83). Beach morphology is not
to the macrofauna, this meiofaunal component may comprise
    A.C. Brown and A. McLachlan

                                  static and may change towards dissipative or reflective
                                  according to conditions, often seasonally.
                                    Sand movements are most apparent during storms, when
                                  large quantities of sand may be eroded from the upper shore
                                  and deposited in the surf zone, to return slowly when
                                  conditions are calmer. Storms are thus of great importance in
                                  shaping and defining the ecosystem. This is as true of shel-
                                  tered sands as of exposed shores (Hegge et al. 1996).
                                  Long-shore sand transport is also typically in evidence and is
                                  critical to the maintenance of the sand budget (Clark 1983).
                                  There is also a flow of biological materials through the
                                  system, essential for nutritional input to an intertidal
                                  community largely lacking primary production. Stranded
                                  wrack or kelp provides food for semi-terrestrial crustaceans
                                  and insects, washed up carrion is important for aquatic crus-
                                  taceans and scavenging gastropods, while filter feeders such
                                  as the clam Donax rely on suspended particles, including
                                  surf-zone diatoms (Brown & McLachlan 1990). Surf-zone
                                  predators invade the intertidal beach as the tide rises, birds
                                  during the day and terrestrial animals may invade it at night.
                                  Bacteria and meiofauna work over organic material in the
                                  sand, returning mineralized nutrients to sea (Griffiths et al.
                                    Dissipative beaches, with their gentle slopes and swash,
                                  present less hostile conditions to the fauna than do reflective
                                  beaches and display higher diversity and biomass. Reflective
                                  beaches are inhabited chiefly by a semi-terrestrial fauna
                                  dependent on wrack or kelp, while increasingly dissipative
                                  conditions lead to greater food-chain complexity. The surf
                                  zone plays an increasingly important role in the bionomics of
                                  the system as conditions become more dissipative, especially
                                  where circulating cells of water support surf diatoms such as
                                  Anaulus, which then drive much of the food web (Fig. 2). A
                                  semi-closed ecosystem results (McLachlan 1980). Reflective
                                  beaches are, in general, net importers of material from the
                                  sea, while dissipative systems are exporters (Brown et al.

Figure 1 Relationship between beach morphodynamic state (
Dean’s parameter) and (a) species richess and (b) macrobenthic
abundance for 23 beaches in Australia, South Africa and the USA.
                                  Figure 2 Simplified food web in a dissipative beach and surf zone,
Ref reflective, Int intermediate, Dis dissipative (after
                                  with primary production dominated by surf-zone diatoms.
McLachlan 1990).
                                                    Sandy shores in 2025    65

FACTORS CURRENTLY IMPACTING SANDY-                 Disruption of sand transport
                                  Any structures or activities which disrupt the transport of
Table 1 provides a summary of impacts affecting sandy        sand either long-shore or vertically on/off shore, may lead to
shores. We will now discuss these in more detail.          serious erosion. This has resulted most obviously from the
                                  construction of harbours, breakwaters, jetties and groins,
                                  which deprive down-drift beaches of sand while updrift sand
                                  accumulates and advances seawards. The most famous case is
Although storms are an important part of a natural cycle      probably that of Madras harbour (Komar 1983a), and some
moulding the morphodynamics of the system, they represent      700 km of the Florida shore are threatened by severe erosion,
the greatest natural hazard faced by sandy-shore animals.      jetties being estimated to account for 85% of the problem
Sand and animals are washed out to sea, while others are      (Finkl 1996). This has led to ongoing artificial beach replen-
stranded upshore, where they die of exposure. Such events      ishment, which is costly and under financial threat.
often result in greater mortality than does predation (Brown    Sometimes it is not apparent why a structure has induced
& McLachlan 1990). Some animals (e.g. the whelk Bullia,       erosion or deposition, but in most cases the effects could have
aquatic isopods and mysids) can regain the shore if not       been predicted with some accuracy if an adequate prior
carried too far out to sea, while others (e.g. clams of the genus  impact study had been undertaken. Sometimes such struc-
Donax) cannot. The ability to survive storms by behavioural     tures have been found to benefit certain categories of fauna,
means is a key feature of sandy-shore animals (Brown 1996),     although these have seldom been planned. For example,
                                  Botton et al. (1994) found that in Delaware Bay shorebirds
but these mechanisms do not always give adequate protec-
tion, especially if significant sand erosion occurs. In       (red knots, sanderling and ruddy turnstones) aggregated near
compensation, as few macrofaunal species can tolerate the      shoreline discontinuities, including jetties that provided
                                  concentrating mechanisms for drifting Limulus eggs.
conditions, interspecific competition is minimized (Little
2000).                                 Groins are constructed with the intention of trapping sand
  In extreme cases, so much sand may be eroded from the      to build up a beach or prevent further erosion. Most often,
beach that rocks below the sand become exposed. This        their purpose has been to protect landward property from the
disrupts the laminar flow of the swash, making colonization     effects of storms. However, bad planning or failure to imple-
by swash-riding species (e.g. Bullia and Donax) impossible     ment the design has frequently led to damage in the very
(Brown et al. 1991b). Some beaches only occur seasonally,      areas they were meant to protect. Even well-designed groins
sand deposited during relatively calm periods being totally     may prove inadequate to protect or restore beach systems, as
removed during the months when storms are prevalent. In       has been demonstrated by the history of the beachfront at
such cases, there may be some colonization by bacteria and     Long Island, New York, USA (Clark 1983), and the groins in
meiofauna as sand is deposited but macrofauna has no time to    Maputo Bay, Mozambique (A.C. Brown, personal obser-
establish itself. More common are beaches which are simply     vation 1997).
too inhospitable to macrofauna for much of the year. Some        Artificial stabilization of dunes by plants or fences can also
species (e.g. the whelk Bullia) remain offshore until storms    have severe effects on sand transport. Some dunefields
have flattened the beach and then colonize it during calmer     receive wind-blown sand from updrift beaches and pass it
weather (Brown 1996). Juvenile Donax may also colonize it      overland to downdrift beaches; stabilization may have
briefly but cannot attain adult size before being washed away    severely detrimental effects on the latter (Tinley 1985; Swart
by the next series of storms.                    & Reyneke 1988). The hardening of surfaces, sea walls and

Table 1 Summary of factors currently impacting sandy shores.
Factors              Extent                Type of beach            Importance / severity
                                     most affected            (max. 10)
Storms               Widespread              Exposed               7
Disruption of sand transport    Near structures            Exposed               6
Pollution             Localized/widespread         Sheltered              6
Trampling             Localized               Vegetated dunes           5
Recreation/tourism         Localized (increasing)        Resorts               4
Litter               Localized (increasing)        Resorts               4
Beach cleaning           Localized               Urban/resort             4
Mining               Localized               Various               3
Groundwater changes        Widespread              Arid areas              3
Bait collecting          Widespread              Beaches with rich fauna       3
Fishing              Widespread              Beaches with rich fauna       3
    A.C. Brown and A. McLachlan

other such structures may also alter sand transport (Kraus &   these typically result in oil pollution, though to a lesser
McDougal 1996). Studies of the effects of sea walls on sedi-   degree (Brown 1985). In addition, oil slicks result from acci-
ment transport have led to apparently contradictory results   dental spillages and from the cleaning out of tanks at sea.
(Miles et al. 2001), which may partly reflect a lack of under-  Spillages from oil terminals and rigs are common and often
standing of the processes involved. Miles et al. (2001) used   result in chronic pollution which may be more damaging to
sophisticated methods to study sediment dynamics in front of   the biota than a single severe oil-pollution event (Dicks &
a sea wall in south Devon, UK, and to make comparisons      Hartley 1982). The beaches of the Congo Republic, West
with an adjacent, natural beach. Sediment suspension and     Africa, are permanently covered in oil and tar due to termi-
transport were both altered significantly by the wall,      nals and offshore drilling, while beaches in and around the
suspended sediment concentrations being up to three times    Arabian Gulf suffer chronic pollution due to heavy tanker
higher and onshore sediment transport reduced; longshore     traffic. Run-off and natural seepages of petroleum hydrocar-
transport was an order of magnitude higher in front of the    bons may also lead to chronic pollution and land-based
wall than on the natural beach (Miles et al. 2001).       pollution may be the most important source of these
  Extensive or regular mining of sand from the shore may    substances for the oceans as a whole (Camp 1989).
have equally severe consequences. Komar (1983b) studied the     Crude oil has a number of effects on sandy-beach biota
effects of removing 12 000 m3 of sand annually from the     (Brown 1985). It has a toxic component, consisting mainly of
beach at Schoolhouse Creek, Oregon, USA. Prior to this      short-chain and polycyclic aromatic hydrocarbons. Secondly,
operation, gains and losses of sand approximately balanced,   the oil has physical effects, clogging delicate filter-feeding
but the sand mining tipped the balance, resulting in long-    mechanisms and appendages. Thirdly, oil may act as a
term erosion. Sand mining of the dunes at Hermanus, near     barrier, reducing oxygen tensions in the sand below it and
Cape Town, South Africa, has totally altered the nature of    reducing water flow through the beach (McLachlan & Harty
the shore (A.C. Brown, personal observation 2000). In prin-   1981a). Recovery from an oil spill takes place in stages. The
ciple, any kind of excavation on any part of a sandy shore    meiofauna may recover within a year (McLachlan & Harty
must be presumed to be damaging to the system (Clark       1981b) and presumably bacterial populations return even
1983).                              sooner. Most macrofaunal species take longer to re-establish
                                 themselves and, in the meantime, opportunistic polychaete
                                 worms of the families Capitellidae and Cirratulidae may
Beach nourishment and bulldozing
                                 increase in numbers or invade the beach if not previously
Beach nourishment by importing sand and bulldozing to      present, and temporarily dominate the system (Southward
restore dunes, by transferring sand from low to high levels,   1982). The macrofauna of fine sediments takes longer to
have become common practices in some parts of the world,     recover than that of coarser beaches and oil trapped in the
such as North Carolina, USA, which face ongoing beach      sand may influence the system for six years or more (Thomas
erosion from man-made structures or from natural causes     1978).
(Leonard et al. 1990; Peterson et al. 2000). At Bogue Banks,     In the past, oil dispersants have often been sprayed too
North Carolina, USA, the imported sand was substantially     near the coast or even on the shore itself, with disastrous
finer than that of the natural beach and had more shelly     effects on the biota. Fortunately, this practice is no longer
material, while bulldozing to augment the primary dune      common. All mixtures of oil and dispersant are more toxic
deposited coarser, more shelly sand than that already present  than is the oil itself (Norton & Franklin 1980).
and reduced the width of the intertidal beach (Peterson et al.    Organic enrichment may result from the discharge of raw
2000). These changes impacted the fauna, the mole crab      or partially treated sewage to sea. The tendency in recent
Emerita and the clam Donax displaying an 86 to 99%        decades to increase the length of discharge pipes in an
decrease after some weeks; both animals had failed to recover  attempt to keep the sewage away from the shore has not
after three months (Peterson et al. 2000). Beach and profile   always been completely effective; however, the current trend
nourishment at Perdido Key, Florida, USA, led to negative    to forbid the discharge of raw sewage may prove beneficial.
impacts on the macrobenthos that were still apparent two     Although sewage generally contains few toxic substances,
years after the event (Rakocinski et al. 1996). Nevertheless,  organic enrichment leads to a lowering of oxygen tensions
beach nourishment has often proved to be an effective way of   within the sand and a consequent upward encroachment of
combating erosion (Peterson et al. 2000). It may also be used  anoxic ‘black layers’. This in turn results in impoverishment
to enhance the habitat of selected species of biota.       of the fauna. A worldwide problem is the glut of phosphorus
                                 and particularly nitrogen, resulting largely from the
                                 increased use of fertilizers (World Resources Institute 1998).
                                 These elements reach the sea through sewage, rivers, run-off
As with other types of shore, sandy beaches suffer pollution   and stormwater drains. Consequent eutrophication,
from a large number of sources. The most spectacular       distorting nutrient cycles and leading to algal blooms and
pollution events have been due to oil tanker accidents.     oxygen deprivation, is a major threat to beaches in sheltered
                                 lagoons and estuaries (Gowen et al. 2000). Observed
Accidents to non-tanker vessels are far more common and
                                                   Sandy shores in 2025    67

                                 Off-road vehicles
increases in toxic algal blooms are considered to be related to
this increased nitrogen input (World Resources Institute
                                 A variety of vehicles, connected with recreation or industry,
                                 may invade a sandy shore, causing different types and degrees
  Factory effluents vary greatly in their impact on sandy
                                 of negative impact. Some recreational vehicles, such as motor-
shores, those that cause the greatest public concern due to
                                 cycles, 4 4 vehicles and vehicles of the ‘beach-buggy’ type,
their colour or smell being not always the most damaging.
                                 with large, wide tyres, driven up and down dunes, often at
Factories have tended to be built on estuaries or shallow shel-
                                 considerable speed, cause displacement of sand and destroy
tered bays, so that sandy or muddy beaches incur much
                                 dune vegetation. This can be extremely damaging in view of
pollution from these sources. In many countries, small
                                 the fragile nature of the dune ecosystem. In addition, shore-
factories discharge effluent into sewers or stormwater drains,
                                 birds are disturbed and their nests, eggs and young may be
the latter frequently opening onto the beach above high-
                                 destroyed. Both these and more conventional vehicles may be
water mark (Brown et al. 1991a). Such drains also often
                                 driven along the beach itself. This often causes little impact
present a health hazard, with high concentrations of faecal E.
                                 along the wet foreshore, although this is not true of all
                                 beaches. On some New Zealand beaches, vast numbers of sand
  Thermal pollution is a factor on some beaches. Factories
                                 dollars (Echinodiscus) dominate the foreshore and are crushed
frequently discharge effluent at a higher temperature than
                                 by vehicles (S.C. Webb, personal communication 2000).
the sea water, thereby adding thermal pollution to chemical
                                 Higher up the slope, vehicles are liable to crush semi-terres-
effects. Such pollution is generally insignificant, however,
                                 trial invertebrates, such as isopods, talitrid amphipods and
and it is only with the advent of large power stations, and
                                 ocypodid crabs on the surface or in their burrows. Wolcott
particularly nuclear power stations, that serious study of the
                                 and Wolcott (1984) considered the negative effects of off-road
effects has been undertaken. Markowski (1959) concluded
                                 vehicles on populations of the crab Ocypode, while Van der
that no detrimental effects could be observed from power
                                 Merwe (1988) reviewed the literature on the impacts of traffic
station cooling water effluent, but later studies (Naylor
                                 on coastal ecosystems. Van der Merwe and Van der Merwe
1965; Nauman & Cory 1969; Hill 1977) concentrated on
                                 (1991) investigated the damaging effects of off-road vehicles
more subtle effects than Markowski had considered and
                                 on the fauna of a beach, including the crushing of Tylos (Fig.
doubted his conclusions. At Hunterston, Scotland, no
                                 3: Y 0.75X – 4.6, r2 0.99, p 0.008) and Brown (2000)
major changes to the beach fauna were noted after the
                                 identified off-road vehicles as a major cause of decline in
power station began operating, but within ten years, the
                                 populations of Tylos granulatus on the South African west
population density of the bivalve Tellina tenuis showed a
                                 coast. Hosier et al. (1981) noted that vehicle tracks in the sand
considerable decline, although the animals grew faster. At
                                 presented barriers to the seaward progress of turtle hatchlings.
the same site, the amphipod Urothöe started breeding
earlier than before and juveniles grew for longer, reaching a
28% greater size (Barnett & Hardy 1969; Barnett 1971).
Siegel and Wenner (1984) reported abnormal reproduction
in Emerita near a nuclear station in Southern California,
  Radioactive pollution affects few beaches, but has been a
source of concern near nuclear power stations and especially
close to nuclear reprocessing plants (McKay et al. 1986).
Plutonium has understandably been the chief focus of atten-
tion. Plutonium from such sources is generally finely
particulate or in solution and tends to bind strongly onto
sediment particles, especially fine particles, affecting marine
life (Brown 1994).
  While pollution of intertidal beaches most commonly
arises from seaborne materials, pollution of the dunes is
more likely from land-based sources. Fertilizer residues
from agricultural land behind the dunes have been found to
effect changes in dune plant communities (Ranwell 1972)
and pesticides may be a problem. Airborne pollution can be
an important factor, in addition to run-off. Polluted
groundwater is likely to seep seawards, thus affecting the
                                 Figure 3 Regression of percentage injury to the semi-terres-
intertidal beach and even the surf zone. More attention
                                 trial oniscid isopod Tylos capensis against off-road vehicle
needs to be devoted to movements of groundwater with
                                 passes. 95% confidence limits are shown (after Van der
regard to both pollution and nutrient transport (Uchiyama
                                 Merwe & Van der Merwe 1991).
et al. 2000).
    A.C. Brown and A. McLachlan

Mining                                although it is measurable and, even in the lower intertidal,
                                   may injure delicate crustaceans and juvenile bivalves (Moffet
Mining activities can have very severe effects on the
                                   et al. 1998).
ecosystem. In addition to removal of sand itself, mining
may take place for precious stones, such as diamonds, or
                                   Beach cleaning
for various minerals. It may be undertaken on the beach
itself or in the surf zone or beyond; in all cases heavy vehi-
                                   Many beaches are regularly cleaned during the holiday
cles and machinery are involved on the beach. Strip
                                   season and in some cases throughout the year. Cleaning
mining of the intertidal beach effectively destroys the
                                   commonly takes the form of clearing the beach not only of
ecosystem. Many animals, including the meiofauna,
                                   debris left behind by visitors, but also of kelp, wrack and
eventually return as the beach re-establishes its former
                                   other dead or stranded biota. This deprives the ecosystem of
characteristics, but some semi-terrestrial Crustacea may
                                   valuable nutritional input, semi-terrestrial forms such as
fail to do so (Brown 2000). Offshore mining can be equally
                                   talitrid amphipods, oniscid isopods and ocypodid crabs being
disruptive, as the material is usually pumped ashore and
                                   the most deprived. Mobile beach-cleaning machines are
the ‘tailings’ left on the beach, altering the beach profile
                                   employed on some beaches. These suck up and filter the
and its particle-size structure. At Elizabeth Bay, in
                                   sand, capturing not only debris, but also any small animals,
Namibia, the dumping of coarse tailings resulted in the
                                   such as talitrids, near the surface. Talitrid populations can be
beach becoming more reflective, with a consequent loss of
                                   effectively eliminated by this process and the mobile
fauna (McLachlan 1996). Mining in the dunes and behind
                                   machines can crush more deeply buried invertebrates in their
them destroys the vegetation and may disrupt sand trans-
                                   burrows. Some of these effects have been studied by
port, in addition to adversely affecting shorebirds. Tailings
                                   Llewellyn and Shackley (1996).
or topsoil run-off from mining behind the dunes may
pollute the beach.
                                   Groundwater level changes
Trampling                              In addition to pollution of groundwater, human activities
                                   commonly result in a lowering of the water table. One such
Trampling associated with recreational activities may have
                                   activity is the drawing off of water for domestic or agricul-
extreme negative effects on dune systems (Fig. 4). These
                                   tural purposes. This may be intensified by the hardening of
include not only direct damage to vegetation and the fauna,
                                   surfaces, so that surface water from rain is diverted to
but also physical impact on the substratum, notably
                                   stormwater drains instead of sinking into the soil. Lowering
compaction, which influences soil moisture, run-off, erosion,
                                   of the dune water table can have serious adverse effects on the
vegetation and micro-organisms (Liddle & Moore 1974). The
                                   dune ecosystem, which in turn may affect the intertidal beach
most obvious effects occur at low levels of trampling, further
                                   (Brown & McLachlan 1990). Flooding, on the other hand,
impact decreasing thereafter. Trampling on the intertidal
                                   raises the water table and hastens erosion.
slope typically has much less impact than in the dunes,

                                   Bait and food collecting
                                   The collection of invertebrates for use as bait is common on
                                   beaches that are stable enough to support the burrows of
                                   prawns such as Callianassa or of the lug worm, Arenicola.
                                   Beach clams are also harvested, for both food and bait, in
                                   some regions attaining the status of commercial enterprise.
                                   Indeed, 15 species of beach clam are harvested extensively
                                   around the world and in several cases overexploitation has led
                                   to the collapse of the fishery (McLachlan et al. 1996).
                                   Nevertheless, while populations are often drastically reduced
                                   by these activities, they are seldom if ever eliminated, as they
                                   reach a level at which the effort of collecting fails to justify
                                   the reward. Recovery thus begins as soon as collecting ceases.
                                   The exploited clam Mesodesma in Uruguay recovered rapidly
                                   after the beach was closed to the fishery for 32 months, and
Figure 4 Relative importance of three kinds of human impact on
                                   recruitment displayed over-compensation (Defeo 1996). In
sandy shores along an exposed gradient. Pollution chiefly affects
                                   northern KwaZulu-Natal, South Africa, ghost crabs
the subaerial beach, trampling and off-road vehicles mainly impact
                                   (Ocypode) and mole crabs (Hippa and Emerita) are harvested
the dunes, while coastal engineering structures permanently alter
                                   in a subsistence fishery; this appears to be sustainable (Kyle
sand budgets for the entire littoral active zone (after Brown &
                                   et al. 1997). In addition to the removal of beach animals,
McLachlan 1990).
                                                    Sandy shores in 2025    69

collecting typically involves digging or the use of prawn     terns have been severely impacted by coastal development
pumps, as well as trampling. The results of these physical     and ecotourism and piping plovers are widely threatened in
disturbances may be more deleterious to the ecosystem than     the USA. Piping plovers in areas less disturbed by people
the actual removal of target animals (Wynberg & Branch       spent more time foraging and less time being vigilant than
1997).                               birds at other sites; the presence of people was stressful for
                                  breeding adults and chicks, possibly accounting for decreased
                                  reproductive success (Burger 1991). Ecotourism affects bird
                                  behaviour, reproductive success and population levels of both
Dissipative surf zones are important nursery areas for fish     breeding and migratory birds in New Jersey, USA, in various
                                  ways (Burger et al. 1995), and frequent human intrusion
(McLachlan 1983; Brown & McLachlan 1990) and are home
to a number of adult species. Both rod-and-line recreational    leads to avian habituation and learning. The exclusion of
fishing and commercial seining have significantly depleted      people from some habitats has had beneficial effects for some
populations of the latter in many areas, thus impacting the    species.
surf-zone system and reducing predation in the intertidal
zone as the tide rises. Recreational fishing commonly involves
off-road vehicles, while seining often results in a bycatch of
sand crabs and other animals of non-commercial value, which    Litter left behind on the beach and in the dunes by human
may be dispatched on the spot or left on the beach to die.     visitors has become an escalating problem. Teagle (1966,
                                  cited in Ranwell 1972) quantified litter deposited in Studland
                                  Dunes, Dorset, during a two-year period and observed some
Recreational activities
                                  impact on the fauna. Since this work, non-biodegradable
The recreational value of sandy beaches can hardly be       plastic materials have become the chief items of litter,
overemphasized. Recreational activities such as swimming,     affecting surf-zone animals as well as those higher up the
wading, surfing, running, dog walking, picnicking, ball       slope. Moore et al. (2001) have recently studied the compo-
games, horseback riding, sand sailing, wave kites, cooking     sition and distribution of beach debris in Orange County,
and building sand castles, must all have some impact,       California. In some regions of the world, litter is simply
although this has never been quantified. In general,        allowed to accumulate, or be washed out to sea. In others, it
recreational pressures decrease sand stability and increase its  is collected but then buried above high-water mark or among
mobility (Carter 1975; Artukhin 1990). However, obser-       the dunes, where it tends to resurface. Only in countries with
vations suggest that impact on the intertidal beach is usually   a commitment to environmental conservation is the litter
slight and that surf-zone invertebrates are little affected. The  removed to landfill or incinerators. An important negative
experiment of Jaramillo et al. (1996), in which a fenced-off    feature of litter is its detraction from the aesthetic value of the
strip of beach was compared with an adjacent area open to the   beach.
public, indicated no significant effect of recreation on the
crustacean infauna of a Chilean beach, probably because sand
                                  LONG-TERM TRENDS
movements due to changes in wave climate overshadowed
physical effects of human disturbance. However, fish,
                                  Accretion and erosion
including elasmobranchs, may be frightened into deeper
                                  Short-term changes in beach morphology, in response to
water (A.C. Brown, personal observation 1975), while shore-
                                  fluctuating wave regimes or weather conditions, are well
birds such as sanderlings are reluctant to come onto the beach
                                  known (Brown & McLachlan 1990; Short 1996).
to feed, possibly resulting in nutritional stress or causing
                                  Superimposed on these are slow, long-term trends in accre-
them to migrate to less populated beaches. On the Florida
                                  tion or erosion, often only apparent over periods of decades
coast, increasing human presence within 100 m of sanderlings
                                  or even centuries. On some beaches, retention of newly-avail-
was found to lead to decreased foraging times of the birds
                                  able sand leads to accretion and the coastline slowly advances
during the day and increased nocturnal foraging (Burger &
                                  seawards. The beach at Hastings, southern England, presents
Gochfeld 1991).
                                  a good example of this process. Parts of Scandinavia have
                                  displayed land uplift of about 1 m per century (Aubrey &
Ecotourism and bird watching
                                  Emery 1993), pushing beaches seawards. Apparently far
                                  more common worldwide is long-term beach erosion, with a
Ecotourism, especially in developed areas with dense human
                                  loss of sediment, diminishing beach volumes and consequent
populations, although it encourages appreciation of coastal
                                  retreat of the coastline; a number of factors, some mentioned
environments, may have a severe impact on coastal bird
                                  above, may be involved in such chronic erosion (Bird 1985).
populations. On the coast of New Jersey, USA, rare birds
                                  In addition, the damming of rivers deprives estuaries and the
attract more attention than common species, adding to their
                                  oceans of the natural fluvial input of sediment. In 1950 there
vulnerability, but bird colonies are more vulnerable to distur-
                                  were 5270 large dams in the world; there are currently in
bance than are isolated individuals (Burger et al. 1995). Least
    A.C. Brown and A. McLachlan

excess of 36 500 (World Resources Institute 1998). Reduction    million people each year (United Nations 1998). This is
of cliff erosion, either by man-made structures or due to     lower than the peak rate of over 2% per year recorded for
natural causes, also reduces the available sediment (Bird     1965–1970, largely because in 61 developed countries the
1985). Long-term reduction in the transport of sand from the    fertility rate (2.1 children or less per woman) approximately
sea floor may also be an important factor. Interception of     balanced the death rate. The fertility rate in some developing
longshore drift by human constructs (see above) or natural     (or ‘emerging’) countries is also dropping and could reach
causes inevitably leads to down-drift beach degradation,      about 2.1 children per woman by the year 2050 (Potts 2000).
while strong onshore winds may effectively remove sand       No such trend is documented for many Third World coun-
from the system by blowing it far enough inland to prevent     tries; for example, Niger currently has 5.7 children per
its return to the beach. Sand may also be reduced in volume    woman, as against 2.6 in South Africa (South African Bureau
due to weathering, brought about by repeated grinding of the    of Statistics, personal communication 2001).
grains by wave action and/or by leaching; finer grains are       The effect of population growth on sandy-shore ecosys-
more easily removed from the system by waves, currents and     tems is intensified by the tendency of people to move to
wind. Excessive precipitation and flooding behind the beach     within a few kilometres of the coast (Roberts & Hawkins
also favour erosion, as the escape of this water to sea carries  1999). In First World countries, this is linked largely to afflu-
sand with it and causes a rise in groundwater. Past sea-level   ence, aesthetic considerations and recreation. In Third
changes must have had marked effects on accretion and       World countries, for example in much of Africa, the
erosion. Coastal emergence leads to coastline advance, while    migration is frequently an attempt to avoid conflicts or popu-
a rise in sea level, as in many areas in recent decades (IPCC   lation pressures inland or is linked to the perception that
[Intergovernmental Panel for Climate Change] 1996a) results    there is more easily-acquired food at the coast. Both factors
in recession and loss of beach sand to the sea floor. Long-     may operate at the same time, as has been seen in
term climatic changes, including changes in rainfall patterns   Mozambique (A.C. Brown, personal observation 1997).
and especially increases in the frequency and/or intensity of     In some developing countries, population growth and
storms, have significant effects on beach dynamics. Sand is     movement towards the coast have been partially mitigated by
characteristically transported to sea during storms, returning   an increasing awareness of environmental issues and practical
slowly in calmer weather; increasing storminess will change    steps to conserve the ecosystem, including legislation. The
this balance and lead to continuing erosion.            South African situation is a good example of this healthy
                                  trend. In the mid-1950s, when one of us (A.C. Brown) began
                                  work on sandy shores, the only restrictions on visitors to the
Global warming
                                  beach were limits on the number of bait animals (e.g. the
                                  clam Donax) that could be removed per person per day, and
Global warming, due to the release of greenhouse gases, and
in particular carbon dioxide, together with the destruction of   these limits were seldom enforced. There was no attempt to
forests, has been under way for at least the last 150 years, but  protect the ecosystem in other ways, conservation had not
has only attracted serious attention in the past two decades or  entered the vocabulary of politicians and there was no port-
so. There is now general agreement that the greenhouse       folio concerned with the environment. Only in the late 1960s
effect poses real and substantial problems for the environ-    did the Minister of Planning become Minister of Planning
ment, including sandy shores (IPCC 2001a,b, c). In addition    and the Environment, and only much later was the latter
to temperature change, sea level rise is implicated as polar ice  function separated to provide a Ministry of Environmental
and glaciers melt, though whether the rise in sea level already  Affairs (later a Ministry of Environmental Affairs and
recorded from many parts of the world (IPCC 1996a, 2001b)     Tourism). Public awareness of conservation issues increased
is a direct result of global warming is somewhat uncertain.    concurrently and brought pressure to bear on government
However, open water now appears at the North Pole and the     bodies to promote conservation in all its aspects. Marine
Northwest Passage is open to shipping. Rising sea levels      reserves were established, often offering total protection to
promote increased erosion of sandy shores. In addition,      the biota, and a number of these included sandy shores. In
global warming may be expected to incur increased stormi-     the past decade, or so, tourism has been given a high priority,
ness, at least in some regions, as well as changes in rainfall   and linked to it a need to step up protection of the environ-
patterns; again, whether the floods and storms of 2000/2001,    ment. On popular beaches, virtually throughout the country,
which were particularly severe, were largely due to global     access is along wooden walkways through the dunes, thus
warming is debatable. Increased storminess results in       protecting the dune ecosystem from trampling. Off-road
erosion, retreat of beaches, dune scarping and dune        vehicles are restricted and conservation laws more strictly
vegetation loss.                          enforced. Commercial initiatives, such as mining, have to
                                  undergo rigorous environmental impact assessment and be
                                  exposed to public participation in planning; the organizations
Pressure of human activities
                                  involved are committed to restoring beaches or dunes
Since 1995 the global human population has increased at a     affected during the operation. Projects such as the Cape
rate of 1.33% a year, representing an addition of roughly 79    Peninsula National Park, which will give added protection to
                                                   Sandy shores in 2025   71

the marine biota, are now popular with the public and taken    1988). These changes are largely related to changes in
seriously by government. There is general awareness of the     productivity, indicating that effects of elevated temperature
need to protect endangered or threatened shore species, such    on beach biota may be indirect.
as the African black oystercatcher and turtles. The          In comparison with El Niño events, sea temperature
Department of Environmental Affairs and Tourism in South      changes between now and the year 2025 due to global
Africa has for some years had a Coastal Management Office      warming are predicted to be gradual (IPCC 2001b), allowing
that issues attractive coloured brochures, written in simple    marine populations some time to adjust and acclimate.
language, for the benefit of the public and local authorities,   Moreover, predicted temperature increases, though signifi-
on the subject of coastal conservation. At the time of writing,  cant, are not such as would be likely to totally disrupt
there is legislation before Parliament to ban all off-road vehi-  sandy-shore ecosystems. These predictions have been revised
                                  from time to time (IPCC 1990, 1992, 1996a, b, 2001b),
cles from beaches and dunes. Regrettably, however,
communication between scientists, legislators and beach      present predictions indicating an atmospheric temperature
managers still leaves much to be desired and the latter gener-   rise of between 1 and 5ºC by the year 2100 (IPCC 2001b).
ally have a poor understanding of management issues and      Temperature rise for the oceans as a whole is likely to be only
how to address them (Brown et al. 2000).              about half this value, although semi-enclosed marine lagoons
                                  and shallow bays may in some regions mirror the atmospheric
                                  temperature rise. In such situations, the worst scenario for
Ozone depletion and enhanced ultraviolet radiation
                                  the year 2025 would appear to be a water temperature
Seasonal variations in the thickness of the ozone layer and    increase of between 1 and 1.25ºC. This is a small change
resulting increases in ultraviolet (UV) radiation (Friedrich &   compared with that experienced by some beaches close to
Reis 2000) present a potential hazard to organisms through a    cooling water discharges from nuclear power stations (P.A.
variety of effects; shallow-water species are not immune to    Cook, personal communication 2001) or those subject to El
these effects, as UV radiation has been shown to penetrate     Niño. Moreover, aquatic sandy-shore animals are in many
water to greater depths than previously supposed (Booth &     regions used to quite rapid changes in temperature and in
Morrow 1997). Reduced productivity of marine ecosystems      areas of upwelling these can be extreme, the temperature
may thus result (Hader 1997; Browman et al. 2000). Impacts     changing by up to 10ºC in an hour or so (Brown &
of increased UV radiation on surf-zone biota, including      McLachlan 1990).
phytoplankton, bacteria, crustaceans and their larvae and fish     Sandy-shore animals seldom experience temperatures
(Browman et al. 2000; Gustavson et al. 2000; Wubben 2000)     close to their upper tolerance levels, an exception being some
are more likely to be apparent than on the beach fauna. Most    ocypodid crabs (Fishelson 1983). All sandy-beach animals are
intertidal species are cryptic, living within the sand, and are  capable of burrowing and of escaping below the sand if
thus protected from changes in solar radiation; most of those   conditions at the surface become hostile. However, if the
that emerge from the sand do so only at night (Brown 1983).    temperature rise were to be added to natural warm-water
                                  events, such as El Niño, in some regions, this combination
                                  could have severe negative impact.
                                    Possible effects of increased temperatures on fish,
In attempting to predict changes in the state of sandy-shore    including effects on proteins, muscle function, cardiovascular
ecosystems by the year 2025, the chief trends to be taken into   performance, reproduction, development and growth,
account are (1) the effects and implications of global       metabolism and increased sensitivity to pollution have been
warming, (2) increasing human pressures, bearing in mind      reviewed (Wood & McDonald 1997). Many of the findings
possible mitigation, and (3) ozone depletion and its effects on  must apply in principle to invertebrates as well. In most
UV radiation.                           cases, however, experimental temperatures far exceeded
                                  those anticipated by the year 2025 and the rise involved was
                                  far more acute.
Global warming
                                    Effects of temperature rise due to global warming up to
Changes in sea temperature can have severe effects on marine    2025 are in general likely to be subtle rather than dramatic.
populations, as witnessed during events such as El Niño. The    Some redistribution of species may be apparent, animals
impacts of El Niño on some South American beaches give an     from the tropics and subtropics tending to invade higher lati-
                                  tudes; the distribution of the clam Donax may change, as it
indication of changes that might be expected from rapid
global warming. On Peruvian beaches, the abundance of       appears to be limited by the 5ºC sea-surface isotherm (Brown
many species plummeted during El Niño events, but this was     & McLachlan 1990). However, some distributional contrac-
followed by rapid recovery when conditions returned to       tion may occur, as some regions, such as Western Europe,
normal (Arntz et al. 1988; Tarazona & Parendes 1992).       may become cooler due to the disruption of currents such as
Subtidal areas that had been anoxic saw an increase in abun-    the Gulf Stream (IPCC 2001b). Changes in temperature
dance and diversity, and extension of vertical distribution in   regimes may affect the growth rates and breeding seasons of
many species during El Niño events (Tarazona et al. 1985,     some sandy-shore species. Among the more subtle effects of
    A.C. Brown and A. McLachlan

temperature change are alterations in the speed of burrowing    with regard to specific sandy shores must have a very low
into the sand by invertebrates (McLachlan & Young 1982).      level of confidence, to the extent that they could be
However, given the time scale and the relatively small       completely misleading.
changes in ambient temperature envisaged, we predict
compensatory metabolic adaptations to temperature change
                                  Direct human pressures
are likely for most species.
  More serious are predicted rises in sea level, due to the    The best estimate of future global human population growth
melting of polar ice and glaciers. Average sea level rise is    is 7.1 billion people by the year 2020 (United Nations 1998)
predicted to be between 15 and 95 cm by the year 2100 (IPCC    and it is predicted that up to 75% of these will live within
2001b), or under 30 cm by 2025. As with temperature        60 km of the coast (Roberts & Hawkins 1999). These figures
changes, this rise will be extremely slow. The mobile, highly   take into account mortality due to the AIDS pandemic and
adaptable sandy-shore biota will not be at direct risk from it.  other factors. However, to predict future pressures on sandy
The most significant threat to them is loss of habitat,       shores by multiplying present pressures by the ratio
especially if sea level rise is accompanied by increased stormi-  of future coastal populations to existing populations
ness. The observed tendency to beach erosion, which is more    would be extremely naive. One reason for this is the increase
common than long-term accretion (see above), will inevitably    in ecotourism, which is economically driven rather than
be enhanced, while beaches on which the sand budget is at     population driven. In developed, and especially in some
present balanced will also suffer erosion and a retreat of the   developing, countries, measures to preserve the coast,
shoreline. Beaches showing long-term accretion (such as      including sandy shores, advance continually and are increas-
Hastings) may well suffer a reversal of this tendency.       ingly the result of well-informed legislation. Although often
  We consider it likely that some narrow beaches will disap-   linked to tourism, this is only part of the story, the public
pear completely, while others lacking dune systems will      becoming increasingly aware of the need for environmental
become severely restricted. Sandy-shore ecosystems that      and biological conservation and protection.
currently incorporate extensive dune systems should suffer       Simple measures often bring about dramatically improved
the least, the habitat remaining essentially unchanged though   results, an example being the construction of wooden walk-
moving landwards. Erosion may be mitigated by beach nour-     ways across the dunes to beaches (Brown & McLachlan
ishment and it is probable that this practice will become more   1990). The dune system is at once protected and this protec-
widespread.                            tion continues even if the number of users doubles. A ban on
  Changes in current patterns and the implications of such    off-road vehicles, if enforced, brings immediate benefit to the
changes are difficult to determine with accuracy (IPCC       biota, and proper environmental impact assessment of new,
2001a,b), but it seems certain that altered patterns will     proposed structures can ensure that the sand budget is not
emerge, inevitably changing sand transport and budgets.      significantly affected. The total exclusion of people from
While most beaches will suffer shoreline retreat, new beaches   areas frequented by rare or endangered species, including
might form in some areas. Another, related, uncertainty is the   birds, brings the species immediate protection. Such
effect of global warming on upwelling; at present opinions     measures are increasingly effected and we anticipate that they
differ as to whether upwelling will increase, decrease or     will continue to be improved in developed and developing
remain relatively unaffected ( J.G. Field, personal communi-    countries, counteracting some of the impact of increasing
cation 2001).                           human pressures.
  Among the less publicized features of enhanced CO2 is the      Measures to reduce pollution must obviously also be taken
prediction that it could lead to increased primary production   into account in projecting the state of sandy shores in 2025.
through its effect on photosynthesis (Melillo et al. 1993).    More and more countries are moving towards the adoption of
Surf-zone diatoms might therefore increase in density and     the London Dumping Convention and the European Union
                                  Directives concerning marine pollution (Figueras et al.
result in enhanced nutritional input to the intertidal beach.
  There have recently been significant advances in the       1997). It is likely that in the near future the discharge of raw
development of mitigating scenarios for greenhouse gas emis-    sewage to sea will be banned in all countries aspiring to a
sions, including the costs of mitigation (IPCC 2001c).       measure of socio-economic stability.
However, even if global greenhouse gas emissions become        In marked contrast to the above, in many relatively under-
stabilized, global warming and all its consequences will      developed countries, especially in Africa, virtually no
continue to increase during the present century because of     measures are taken to protect the environment. More than
the lag in climate response (Wigley 1995).             half the countries in Africa have been involved in civil war in
  Predicted global patterns of change resulting from global    the last few decades, and political instability is the norm
warming suffer from a considerable measure of uncertainty.     rather than the exception. In these circumstances, conserva-
This is especially true for secondary effects such as increased  tion is hardly ever mentioned and what legislation there
storminess and changes in current patterns, including       might be is not enforced. To make matters worse, sandy
upwelling (IPCC 2001b). At local or regional levels, there is   shores generally come low down on any list of conservation
even greater uncertainty and any quantitative projections     priorities, long behind rocky shores, as used to be the case in
                                                  Sandy shores in 2025    73

                                 CONCLUSIONS AND MANAGEMENT
more developed countries. While it is feasible that some of
these African countries will have attained a measure of stab-
ility over the next quarter century and begin to devote time
and energy to conservation matters, in most cases this hope is  Sandy shores are dynamic environments for which the over-
remote. Exploding population growth, poverty, AIDS,        riding process is the action of waves and tides on the available
unemployment, economic ills and crises of governance are     sediment. This and aeolian sand transport higher up the
likely to be the order of the day until at least 2025, even if  slope determine the physical characteristics of the shore,
internal conflicts cease, completely overshadowing environ-    which in turn determine the constitution of the biota. The
mental concerns.                         ecosystem comprises dunes, beach face and surf zone, with
                                 exchanges of material among these three entities. The fauna
                                 inhabiting these shores is extremely mobile and adaptable to
Ozone depletion and increased UV radiation
                                 changing conditions. Figure 5 summarizes the factors
Increased UV radiation would have rather less effect on      impacting sandy shores.
sandy shores than on most other ecosystems, only the biota of    The chief long-term threat to these systems, virtually
the surf zone being at real risk. However, the consensus of    worldwide, is increasing erosion resulting largely from sea
scientific opinion is that, thanks to reduction in the emission  level elevation and increased storminess associated with
of aerosols which lead to ozone depletion, further depletion is  global warming, the damming of rivers, preventing sediment
unlikely, the phenomenon having either peaked or being      flow to the sea, and sea walls and other structures that alter
about to do so (Friedrich & Reis 2000).              sand transport. It is predicted that beach nourishment, as a

Figure 5 Summary of some factors impacting sandy shores.
    A.C. Brown and A. McLachlan

means of combating erosion, will be increasingly employed in     Strict control over routes of access, particularly through
developed countries, and may significantly influence sandy-     the dunes, needs to be enforced universally. Limiting the
shore ecology in the future. Temperature rise by the year     number of people allowed on the beach may also be benefi-
2025 is predicted to have only subtle effects, but projected   cial, as may the exclusion of the public from certain areas
changes in current patterns may significantly alter sand trans-  harbouring threatened species.
port, making erosion more rapid in some instances, but        Off-road vehicles must be forbidden, except under rare,
possibly favouring accretion in others.              unavoidable circumstances, such as an attempt to save human
  While human populations near the coast are expected to     life. Beach-cleaning machines should not be employed.
increase, in some cases dramatically, and ecotourism escalates,    Exploitation of beach animals for food or bait must be
increased pressure on sandy shores may well be mitigated by    strictly controlled, in order to be sustainable, and disallowed
improved legislation and management resulting from a better    in some areas.
understanding of sandy-shore processes. Underdeveloped        Special attention needs to be accorded to threatened
countries, especially in Africa, are expected to lag behind in  species of shorebirds and turtles which come ashore to breed.
this regard, with increasing pressures on the ecosystems.     Total protection of such species needs to be the aim. More
  It is not expected that increased UV radiation will have    reserves need to be created, especially where threatened
significant effects on the biota.                 species are concerned.
  There is a considerable measure of uncertainty about rates     Beach managers and would-be developers should always
of expected climate change and sea level rise due to global    be kept well informed not only about legislation, but also as
warming (IPCC 2001b) and even greater uncertainty with      to why these measures are considered necessary. Such infor-
regard to changes in ocean current patterns and increased     mation needs to be provided in simple language and, if
storminess. Some uncertainty also exists with regard to poss-   possible, in attractive format.
ible reductions in UV radiation and the effects of increasing
human pressure on sandy shores. Added to this is the fact
that only for very few beaches are existing parameters quan-
                                 Arntz, W.E., Valdivia, E. & Zeballos, J. (1988) Impact of El-Niño
tified satisfactorily. Predictions of impacts by the year 2025
                                  1982-83 on the commercially exploited invertebrates (Mariscos)
are of necessity both tentative and qualitative.
                                  of the Peruvian shore. Meeresforshung 32: 3–22.
                                 Artukhin, Y.V. (1990) Anthropogenic effects on recreational
Management needs                          beaches. In: Recreational Uses of Coastal Areas, ed. P. Fabbris,
                                  pp. 231–234. Amsterdam, The Netherlands: Kluwer Academic
There is a need in many countries for improved legislation     Publications.
with regard to protection of the environment and of the biota.  Aubrey, D.G. & Emery, K.O. (1993) Recent global sea levels and land
This applies especially to sandy shores, which are often still   levels. In: Climate and Sea Level Changes: Observations, Projections
accorded a low priority or even left out of consideration. In    and Implications, ed. R.A. Warrick, E.M. Barrow & T.M.L.
many instances, it is assumed that the only reason for       Wigley, pp. 45–56. Cambridge, UK: Cambridge University Press.
                                 Barnett, P.R.O. (1971) Some changes in intertidal sand communi-
ensuring apparently pristine beaches is to attract tourists and
                                  ties due to thermal pollution. Proceedings of the Royal Society of
holiday-makers; this attitude must be revised. The protection
                                  London, Series B 177: 353–364.
of rare and endangered species is important in its own right
                                 Barnett, P.R.O. & Hardy, B.L.S. (1969) The effects of temperature
in preserving the integrity of the ecosystem and biodiversity.
                                  on the benthos near the Hunterston generating station, Scotland.
  Top priority must be given to the avoidance and rejection
                                  Chesapeake Science 18: 255–256.
of structures or activities that may reduce natural sand trans-  Bird, E.C.F. (1985) Coastline Changes: a Global Review. Chichester,
port either longshore or up and down the shore. Any impact     UK: Wiley-Interscience.
assessment must clearly take into account projected sea level   Booth, C.R. & Morrow, J.H. (1997) The penetration of UV into
rise, as well as possibly increased erosion of the shore. The    natural waters. Photochemistry and Photobiology 65: 254–257.
foredunes should be protected as far as possible.         Botton, M.L., Loveland, R.E. & Jacobsen, T.R. (1994) Site selec-
  An important counter to erosion is beach nourishment,      tion by migratory shorebirds in Delaware Bay, and its relationship
                                  to beach characteristics and abundance of Horseshoe Crab
which is infinitely preferable to the construction of sea walls
                                  (Limulus polyphemus) eggs. Auk 111: 605–616.
and other structures. However, in order to protect the biota,
                                 Browman, H.I., Rodriguez, C.A., Beland, F., Cullen, J.J., Davis,
beach profiles should be changed as little as possible and
                                  R.F., Kouwenberg, J.H.M., Kuhn, P.S., McArthur, B., Runge,
every effort should be made to ensure that the new sediment
                                  J.A., St-Pierre, J.F. & Vetter, R.D. (2000) Impact of ultraviolet
deposited is similar to that occurring naturally.
                                  radiation on marine crustacean zooplankton and ichthyoplankton:
  The construction of groins may be beneficial in some situ-    a synthesis of results from the estuary and Gulf of St Lawrence,
ations, not only to protect the physical beach, but also to     Canada. Marine Ecology Progress Series 199: 281–311.
provide refuge for certain shorebirds and other threatened    Brown, A.C. (1983) The ecophysiology of sandy-beach animals – a
species. Such constructs need careful planning and execution    partial review. In: Sandy Beaches as Ecosystems, ed. A. McLachlan
and a thorough knowledge of sand transport and budgets in      & T. Erasmus, pp. 575–605. The Hague, the Netherlands: W.
the area is mandatory.                       Junk.
                                                       Sandy shores in 2025     75

                                    Friedrich, R. & Reis, S. (2000) Tropospheric Ozone Abatement.
Brown, A.C. (1985) The Effects Of Crude Oil Pollution On Marine
 Organisms. Pretoria, South Africa: South African National        Berlin, Germany: Springer-Verlag.
                                    Gibbs, R.J., Matthews, M.D. & Link, D.A. (1971) The relationship
 Scientific Programmes Report No. 99.
                                     between sphere size and settling velocity. Journal of Sedimentary
Brown, A.C. (1994) Plutonium and marine life. Transactions of the
                                     Petrology 41: 7–18.
 Royal Society of South Africa 49: 213–224.
                                    Gourlay, M. (1968) Beach and dune erosion tests. Delft Hydraulics
Brown, A.C. (1996) Behavioural plasticity as a key factor in the
                                     Laboratory Report No. M935/M936, the Netherlands.
 survival and evolution of the macrofauna on exposed sandy
 beaches. Revista Chilena de Historia Natural 69: 469–474.       Gowen, R.J., Mills, D.K. Trimmer, M. & Nedwell, D.B. (2000)
Brown, A.C. (2000) Is the sandy-beach isopod Tylos granulatus an     Production and its fate in two coastal regions of the Irish Sea: the
                                     influence of anthropogenic nutrients. Marine Ecology Progress
 endangered species? South African Journal of Science 96: 466.
                                     Series 208: 51–64
Brown, A.C. (2001) Biology of sandy beaches. In: Encyclopedia of
 Ocean Sciences, Volume 5, ed. J.H. Steele, S.A. Thorpe & K.K.     Griffiths, C.L., Stenton-Dozey, J.M.E. & Koop, K. (1983) Kelp
                                     wrack and energy flow through a sandy beach. In: Sandy Beaches
 Turekian, pp. 2496–2504. London, UK: Academic Press.
                                     as Ecosystems, ed. A. McLachlan & T. Erasmus, pp. 547–556. The
Brown, A.C. & McLachlan, A. (1990) Ecology of Sandy Shores.
                                     Hague, the Netherlands: W. Junk.
 Amsterdam, the Netherlands: Elsevier.
                                    Gustavson, K., Garde, K., Wangberg, S.-A. & Selmer, J.-S. (2000)
Brown, A.C., Davies, B.R., Day, J.A. & Gardiner, A.J.C. (1991a)
 Chemical pollution loading of False Bay. Transactions of the Royal   Influence of UV-B radiation on bacterial activity in coastal waters.
                                     Journal of Plankton Research 22: 1501–1511.
 Society of South Africa 47: 703–716.
                                    Hader, D.P. (1997) Effects of UV radiation on phytoplankton. In:
Brown, A.C. McLachlan, A., Kerley, G.I.H. & Lubke, R.A. (2000)
                                     Advances in Microbial Ecology, ed. J.G. Jones, pp. 1–26. New
 Functional ecosystems: sandy beaches and dunes. In: Summary
 Marine Biodiversity Status Report for South Africa, ed. B.D.      York, USA: Plenum Press.
                                    Hegge, B., Elliot, I. & Hsu, J. (1996) Sheltered sandy beaches of
 Durham & J.C. Pauw, pp. 4–5. Pretoria, South Africa: National
                                     southwestern Australia. Journal of Coastal Research 12: 748–760.
 Research Foundation.
                                    Hill, B.J. (1977) The effect of heated effluent on egg production in
Brown, A.C., Wynberg, R.P. & Harris, S.A. (1991b) Ecology of
                                     the estuarine prawn Upogebia africana (Ortmann). Journal of
 shores of mixed rock and sand in False Bay. Transactions of the
                                     Experimental Marine Biology and Ecology 29: 291–302.
 Royal Society of South Africa 47: 563–573.
                                    Hosier, P.E., Kochhar, M. & Thayer, V. (1981) Off-road vehicle
Burger, J. (1991) Foraging behaviour and the effects of human
 disturbance on the Piping Plover (Charadrius melodus). Journal of    and pedestrian track effects on the sea-approach of hatchling
                                     Loggerhead Turtles. Environmental Conservation 8: 158–161.
 Coastal Research 7: 39–52.
                                    IPCC (1990) Climate Change: the IPCC Scientific Assessment, ed.
Burger, J. & Gochfeld, M. (1991) Human activity influence and
 diurnal and nocturnal foraging of Sanderlings (Calidris alba).     J.T. Houghton, G.J. Jenkins & J.J. Ephraums. Cambridge, UK:
 Condor 93: 259–265.                           Cambridge University Press.
                                    IPCC (1992) Climate Change 1992: the Supplementary Report to the
Burger, J., Gochfeld, M. & Niles, L.J. (1995) Ecotourism and birds
                                     IPCC Scientific Assessment, ed. J.T. Houghton, B.A. Callander &
 in coastal New Jersey: contrasting reponses of birds, tourists and
 managers. Environmental Conservation 22: 56–65.             S.K. Varney. Cambridge, UK: Cambridge University Press.
                                    IPCC (1996a) Climate Change 1995: Impacts, Adaptations and
Camp, C.R. (1989) Oil in the marine environment. In: Marine
                                     Mitigation of Climate Change. Contribution of Working Group II to
 Pollution – a 1988 Perspective, ed. A.G.S. Moldan & J.H. Richter,
                                     the Second Assessment Report of the Intergovernmental Panel on
 pp. 63–65. Pretoria, South Africa: CSIR, South African National
                                     Climate Change, ed. R.T. Watson, M.C. Zinoyowera & R.H.
 Scientific Programmes Report No. 161.
                                     Moss. Cambridge, UK: Cambridge University Press.
Carter, R.W.G. (1975) The effect of human pressures on the coast-
                                    IPCC (1996b) Climate Change 1995: The Science of Climate Change.
 lines of County Londonderry and County Antrim. Irish
                                     Contribution of Working Group I to the Second Assessment Report of
 Geography 5: 72–85.
                                     the Intergovernmental Panel on Climate Change, ed. J.T.
Clark, J.R. (1983) Coastal Ecosystem Management. Malabar, Florida,
                                     Houghton, L.G. Meira Filho, J. Bruce, H. Lee, B.A. Callander,
 USA: R.E. Krieger Publishing Co.: 928 pp.
                                     N. Harris, A. Kattenberg & K. Maskell. Cambridge, UK:
Defeo, O. (1996) Experimental management of an exploited sandy
 beach bivalve population. Revista Chilena de Historia Natural 69:    Cambridge University Press.
                                    IPCC (2001a) Climate Change 2001: The Scientific Basis.
                                     Contribution of Working Group I to the Third Assessment Report of
Dicks, B. & Hartley, J.P. (1982) The effects of repeated small oil
                                     the Intergovernmental Panel on Climate Change, ed. J.T.
 spillages and chronic discharges. Philosophical Transactions of the
 Royal Society of London, Series B 297: 285–307.             Houghton, Y. Ding, D.J. Griggs, M. Nogeur, P.J. van der Linden
                                     & D. Xiaosu. Cambridge, UK: Cambridge University Press.
Figueras, M.J., Polo, F., Inza, I. & Guarro, J. (1997) Past, present
                                    IPCC (2001b) Climate Change 2001: Impacts, Adaptations and
 and future perspectives of the EU bathing water directive. Marine
                                     Vulnerability. Contribution of Working Group I to the Third
 Pollution Bulletin 34: 148–156.
                                     Assessment Report of the Intergovernmental Panel on Climate Change,
Finkl, C.W. (1996) What might happen to America’s shoreline if
                                     ed. J. J. McCarthy, O.F. Canziani, N.A. Leary, D.J. Dokken &
 artificial beach replenishment is curtailed: a prognosis for south-
                                     K.S. White. Cambridge, UK: Cambridge University Press.
 eastern Florida and other sandy regions along regressive coasts.
                                    IPCC (2001c) Climate Change 2001: Mitigation. Contribution of
 Journal of Coastal Research 12: iii–ix.
                                     Working Group I to the Third Assessment Report of the
Fishelson, L. (1983) Population ecology and biology of Dotilla
                                     Intergovernmental Panel on Climate Change, ed. B. Metz, O.
 sulcata (Crustacea, Ocypodidae) on sandy beaches of the Red Sea.
 In: Sandy Beaches as Ecosystems, ed. A.McLachlan & T. Erasmus,     Davidson, R. Swart & J. Pan. Cambridge, UK: Cambridge
                                     University Press.
 pp. 643–654. The Hague, the Netherlands: W. Junk.
    A.C. Brown and A. McLachlan

                                     ments of sediment dynamics in front of a seawall. Journal of
Jaramillo, E., Contreras, H. & Quijon, P. (1996) Macroinfauna and
                                     Coastal Research 17: 195–206.
 human disturbance in a sandy beach of south-central Chile.
 Revista Chilena de Historia Natural 69: 655–663            Moffet, M.D., McLachlan, A., Winter, P.E.D. & de Rouyok,
                                     A.M.C. (1996) Impact of trampling on sandy beach fauna. Journal
Komar, P.D. (1983a) Coastal erosion in response to the construction
                                     of Coastal Conservation 4: 87–90.
 of jetties and breakwaters. In: Handbook of Coastal Processes and
 Erosion, ed. P.D. Komar. Boca Raton, Florida, USA: CRC Press.     Moore, S.L., Gregorio, D. & Carreon, M. (2001) Composition and
                                     distribution of beach debris in Orange County, California. Marine
Komar, P.D. (1983b) The erosion of Siletz Spit, Oregon. In:
                                     Pollution Bulletin 42: 241–245.
 Handbook of Coastal Processes and Erosion, ed. P.D. Komar. Boca
                                    Nauman, J. & Cory, R.L. (1969) Thermal additions and epifaunal
 Raton, Florida, USA: CRC Press.
                                     organisms at Chalk Point, Maryland. Chesapeake Science 18:
Kraus, N.C. & McDougal, W.G. (1996) The effects of seawalls on
 the beach: Part 1, an updated literature review. Journal of Coastal   218–226.
 Research 12: 691–701.                         Naylor, E. (1965) Effects of heated effluents upon marine and estu-
                                     arine organisms. Advances in Marine Biology 3: 63–103.
Kyle, R., Robertson, W.D. & Binnie, S.L. (1997) Subsistence shell-
                                    Norton, M.G. & Franklin, F.L. (1980) Research into toxicity evalu-
 fish harvesting in the Maputaland Reserve in northern
 KwaZulu-Natal, South Africa: sandy beach organisms. Biological     ation and control criteria of oil dispersants. Fisheries Research
 Conservation 82: 173–182.                        Technical Reports, Lowestoft, UK, No. 57: 20 pp.
                                    Peterson, C.H., Hickerson, D.H.M & Johnson, G.G. (2000) Short-
Leonard, L., Clayton, T. & Pilkey, O. (1990) An analysis of replen-
                                     term consequences of nourishment and bulldozing on the
 ished beaches design parameters on US east coast barrier islands.
                                     dominant large invertebrates of a sandy beach. Journal of Coastal
 Journal of Coastal Research 6: 1057–1068.
                                     Research 16: 368–378.
Liddle, M.J. & Moore, K.G. (1974) The microclimate of sand dune
                                    Potts, M. (2000) The unmet need for family planning. Scientific
 tracks: the relative contribution of vegetation removal and soil
                                     American 282: 75–77.
 compression. Journal of Applied Ecology 12: 1057–1068.
Little, C. (2000) The Biology of Soft Shores and Estuaries. Oxford,   Rakocinski, C.F., Heard, R.W. & LeCroy, S.E. (1996) Responses by
                                     macrobenthic assemblages to extensive beach restoration at
 UK: Oxford University Press.
                                     Perdido Key, Florida, USA. Journal of Coastal Research 12:
 cleaning on invertebrate populations. British Wildlife 7:147–155    326–353.
                                    Ranwell, D.S. (1972) Ecology Of Salt Marshes And Sand Dunes.
Markowski, S. (1959) The cooling water of power stations, a new
                                     London, UK: Chapman and Hall: 258 pp.
 factor in the environment of marine and freshwater invertebrates.
 Journal of Animal Ecology 28: 243–259.                Roberts, C.M. & Hawkins, J.P. (1999) Extinction risk in the sea.
                                     Trends in Ecology and Evolution 14: 241–246.
Masselink, G. & Short, A.D. (1993) The effect of tide range on
                                    Short, A.D. (1993a) Beaches Of The New South Wales Coast, A
 beach morphodynamics and morphology: a conceptual beach
                                     Guide To Their Nature, Characteristics, Surf And Safety. Sidney,
 model. Journal of Coastal Research 9: 785–800.
                                     Australia: Australian Beach Safety and Management Program,
McKay, W.A., Johnson, C.E. & Branson, J.R. (1986)
                                     University Printing Service, University of Sydney: 358 pages.
 Environmental radioactivity in Caithness and Sutherland. Part 3:
                                    Short, A.D., ed. (1993b) Beach and Surf Zone Morphodynamics.
 initial measurements and modelling in inshore waters. Nuclear
                                     Journal of Coastal Research, Special Issue No. 15. Lawrence, USA:
 Energy 27: 321–335.
                                     Coastal Eduction & Research Foundation: 231 pp.
McLachlan, A. (1980) Exposed sandy beaches as semi-closed
 ecosystems. Marine Environmental Research 4: 59–63.          Short, A.D. (1996) The role of wave height, period, slope, tide range
                                     and embaymentisation in beach classification: a review. Revista
McLachlan, A. (1983) Sandy beach ecology – a review. In: Sandy
                                     Chilena de Historia Natural 69: 589–604.
 Beaches as Ecosystems, ed. A. McLachlan & T. Erasmus,
                                    Short, A.D. & Hesp, P.A. (1982) Wave, beach and dune interactions
 pp. 321–380. The Hague, the Netherlands: W. Junk.
                                     in southeastern Australia. Marine Geology 48: 259–284.
McLachlan, A. (1996) Physical factors in benthic ecology; effects of
 changing sand particle size on beach fauna. Marine Ecology      Siegel, P.R. & Wenner, A.M. (1984) Abnormal reproduction of the
                                     sand crab Emerita analoga in the vicinity of a nuclear generating
 Progress Series 131: 205–217
                                     station in Southern California. Marine Biology 80: 341–345.
McLachlan, A. & Harty, B. (1981a) Effects of oil on water filtration
 by exposed sandy beaches. Marine Pollution Bulletin 12: 374–378.   Southward, A.J. (1982) An ecologist’s view of the implications of the
                                     observed physiological and biochemical effects of petroleum
McLachlan, A. & Harty, B. (1981b) Effects of crude oil pollution on
                                     compounds on marine organisms and ecosystems. Philosophical
 the supralittoral meiofauna of a sandy beach. Marine
                                     Transactions of the Royal Society of London, Series B 297: 241–255.
 Environmental Research 7: 71–80.
                                    Swart, D.H. & Reyneke, P.G. (1988) The role of driftsands at
McLachlan, A. & Young, N. (1982) Effects of low temperatures on
                                     Waenhuiskrans, South Africa. In: Journal of Coastal Research,
 the burrowing rates of four sandy beach molluscs. Journal of
                                     Special Issue No. 3, ed. C.W. Finkl, Jr, pp. 97–102. Lawrence,
 Experimental Marine Biology and Ecology 65: 275–284.
                                     USA: Coastal Education & Reaearch Foundation
McLachlan, A., Dugan, J.E., Defeo, O., Ansell, A.D., Hubbard,
                                    Tarazona, J. & Parendes, C. (1992) Impacto de les eventos El–Niño
 D.M., Jaramillo, E. & Penchaszadeh, P. (1996) Beach clam fish-
 eries. Oceanography and Marine Biology, an Annual            sobre las commundades bentonicas de playa arenosa durante
 Review 34: 163–232.                           1976-1986. Paleo ENSO Records International Symposium,
                                     Lima, Extended Abstracts, pp. 299–303.
Melillo, J.M., McGuire, A.D., Kicklighter, D.W., Moore, B.,
                                    Tarazona, J., Arntz, W., Canahuire, E., Ayala, Z. & Robles, A.
 Vorosmarty, C.J. & Schloss, A.L. (1993) Global climate change
 and terrestrial net primary production. Nature (London) 363:      (1985) Modificacion producidas durante ‘El-Niño’ en la infauna
                                     bentonica de areas someras del ecosistema de afloriamento
                                     peruano. In: El-Jernomeno El-Niño y su Impacto en la Fauna
Miles, J.R., Russell, P.E. & Huntley, D.A. (2001) Field measure-
                                                     Sandy shores in 2025    77

 Marina, ed. W. Arntz, A. Landa & J. Tarazona, pp. 55–63.       Van der Merwe, D. & Van der Merwe, D. (1991) Effects of off-road
                                     vehicles on the macrofauna of a sandy beach. South African
 Callao, Peru: Bolletin Instituto del Mardel, Special Issue 1985.
                                     Journal of Science 87: 210–213.
Tarazona, J., Salzwedel, H. & Arntz, W. (1988) Oscillations of
 macrobenthos in shallow waters of the Peruvian central coast     Wigley, T.M.L. (1995) Global-mean temperature and sea level
 induced by the El-Niño 1982-83. Journal of Marine Research 46:     consequences of greenhouse gas stabilization. Geophysical
                                     Research Letters 22: 45–48.
Thomas, M.L.H. (1978) A comparison of oiled and unoiled inter-     Wolcott, T.G. & Wolcott, D.L. (1984) Impact of off-road vehicles
 tidal communities in Chedabucto Bay, Nova Scotia. Journal of the    on macroinvertebrates of a mid-Atlantic beach. Biological
 Fisheries Research Board of Canada 35: 707–716.            Conservation 29: 217–240.
Tinley, K.L. (1985) Coastal Dunes of South Africa. Pretoria, South   Wood, C.M. & McDonald, D.G., eds. (1997) Global Warming:
                                     Implications for Freshwater and Marine Fish. Cambridge, UK:
 Africa: CSIR, South African National Scientific Programmes
 Report No. 109: 300 pp.                        Cambridge University Press: 425 pp.
                                    World Resources Institute (1998) World Resources 1998–1999. New
Uchiyama, Y., Nadaoka, K., Rolke, P., Adachi, K. & Yagi, H.
 (2000) Submarine groundwater discharge into the sea and associ-    York, USA: World Resource Institute, Oxford University Press.
 ated nutrient transport in a sandy beach. Water Resources Research  Wright, L.D. & Short, A.D. (1984) Morphodynamic variability of
 36:1467–1479.                             surf zones and beaches: a synthesis. Marine Geology 58: 93–118.
United Nations (1998) World Population Prospects: the 1998 Revision,  Wubben, D.L. (2000) UV-induced mortality of zoea I larvae of
 Volume 1. New York, USA: United Nations Secretariat,          brown shrimp Crangon crangon (Linnaeus, 1758). Journal of
                                     Plankton Research 22: 2095–2104.
 Department of Economic and Social Affairs, Population Division:
 614 pp.                               Wynberg, R.P. & Branch, G.M. (1997) Trampling associated with
                                     bait-collection for sandprawns Callianassa kraussi Stebbing:
Van der Merwe, D. (1988) The effects of off-road vehicles (ORVs)
                                     effects on the biota of an intertidal sandflat. Environmental
 on coastal ecosystems – a review. Institute for Coastal Research,
                                     Conservation 24: 139–148.
 University of Port Elizabeth, Port Elizabeth, South Africa: 64 pp.
by Carrie Kappel last modified 31-05-2006 10:53

Built with Plone