Sand dunes are vital
to the survival of beaches and protect homes and habitats further
inshore from salt spray and sand. Beaches, with their associated
sand banks and sand dunes, are coastal shock absorbers, diffusing
the impact of ocean waves.
Over 100,000 hectares
of New Zealand coastline are covered with dunes. Auckland's west
coast and the Ninety Mile Beach in Northland have the largest
dunes, often extending several kilometres inland. Giant sand dunes
over 100 metres high are unusual, perhaps reflecting long periods
of dune construction in the past. More often sand dunes are 10
to 50 metres high, representing huge reserves of sand to protect
and maintain our beaches.
The soft sands are created by
years and years of the water grinding stones and animal skeletons
into tiny particles. The sand is a fluid environment, moving all
the time, gathering slowly into huge dunes and then, during storms,
shifting back out to sea to form a wide shallow bar that trips
up the incoming waves. This cycle
is important in the long term stability of the shoreline.
The sand dunes are
part of the natural cycle of shore protection and the plants and
animals that live on them contribute to this dynamic process.
Spinifex grass and pingao or golden sand sedge, for example, help
trap the wind-blown sand and it's roots hold, but do not completely
stabilise, the sand dunes. Imported Marram grass tends to stabilise
the sand dunes resulting in a loss of resiliency.
Unfortunately, sand
dunes are also convenient places to mine sand for making glass
or to obtain minerals such as iron. Sand dunes also block rapid
access to the beach as well as the scenic view for houses built
near the beach. Many of New Zealand's sand dunes have been degraded
by mining, road construction, residential and tourism construction,
heavy recreational use (including kids sliding down the face of
dunes), pets (dogs chasing and killing birds nesting on dunes),
imported plants, and off-road vehicles.
Several regional councils,
like Environment Waikato, Bay of Plenty and Auckland, have fostered
community based "Dune Care" or "Beach Care"
projects to help restore the sand dunes and protect the beaches.
Restoration of native plant communities on sand dunes. Bergin and Herbert 1994. What's new in Forest Research. No. 232. New Zealand Forest Research Institute, Private Bag 3020, Rotorua.
Dune Care. by Eric Hamilton, Forest and Bird February 1996.
Sand Dunes in the Waikato Region. Environment Waikato Regional Council. Sea Week 1996.
