Ecosystem Guidelines for Environmental Assessment

COASTAL
SANDY BEACHES
& DUNE SYSTEMS
COASTAL ECOSYSTEMS
Barry Clark and Charl de Villiers
What are the key ecological “drivers” in terms of
maintaining ecosystem function, pattern or structure
The natural oceanic wave climate.
Mobility of sand is critical, particularly between frontal dunes and the beach, as are the seasonal
cycles of deposition (summer) and erosion (winter).
The deposition and decomposition of organic material such as kelp and carrion at the high water
mark and on the back beach allows terrestrial animals to export energy from the beach system inland
to the dunes.
Sand mobility corridors (e.g. inland-trending dune fields, headland bypass and climbing-falling dunes)
promote diversification of terrestrial plant species. Sand mobility also helps drive vegetation structure
and successional dynamics in dune systems.
Coastal thicket vegetation, as occurs on frontal dunes, is critical for maintaining ecological
processes and the major biogeographical gradients - both longitudinally and in relation to the major
drainage systems.
What are the key issues, vulnerabilities and threats
Stabilisation of naturally dynamic dune systems and sediment corridors due to infestation by
rooikrans Acacia cyclops or for the purposes of property and other development has a significant impact
on the integrity of coastal processes.
Resort and housing developments on primary dune systems (including hummock, primary dunes,
dune slack and secondary dunes) are destroying highly sensitive dune systems in certain areas. Examples
of this type of development pressure can be found at Wilderness, Keurboomstrand, Hartenbos,
St Francis Bay, Dana Bay and Victoria Bay.
Linked to development is the disturbance of natural dune vegetation cover due to trampling, driving
or earth-moving operations. This results in erosion and degradation of primary and foredunes, and
mobilisation of driftsand.
Infrastructure that impedes longshore drift and inshore sediment dynamics.
Mortality and disturbance of sensitive beach fauna by Off-road Vehicles (ORVs).
Mining - particularly diamond mining on the West Coast but also sand mining which, in turn, can give
rise to the type of "downstream" disturbances that are often associated with coastal property
development.
Altered erosion patterns can result from the hardening of adjacent shorelines (land reclamation) and
the construction of breakwaters and groynes.
There is an increasing risk of coastal erosion associated with rising sea levels (and particularly when
there is a combination of spring high tides, storm surges and inadequate development setback lines
and degraded primary and foredunes).
Harvesting of drift kelp.
COLIN PATERSON-JONES
28 : SANDY BEACHES & DUNE SYSTEMS