New Zealand's Sea Shore
Key ideas about coastal areas
- New Zealand's coastline is more than 15,134 kilometres long.
This measurement is not very exact. The more detailed the measurement,
the longer the coastline gets! If someone could measure every
single little indentation and every edge of every rock of every
size, the coastline of New Zealand would be millions of kilometres
long. The coastline includes a large variety of coastal environments
including estuaries, bays,
beaches, sand flats, and rocky shores.
- In an ecological sense, the edge of the sea goes into bays and
estuaries and even up rivers to little creeks high in the mountains.
The water flow is unbroken from mountain to ocean and anything
put into the water winds up in the sea.
- While the coastline is very long, it is not very wide. On a vertical
shore, it is only a few metres wide, extending from the lowest
low tide line to the highest tide line. There is a spray zone
above the high tide line where waves spray salt water and a surge
zone below low tide where strong wave action scours the bottom.
- Where the slope of the shore is gradual, as on a gently sloping
beach or tidal flat, the width of the coastal area is broader,
but not often more than a few hundred metres.
- Tides are caused by the gravitational pull of the moon and the
sun. They are highest (spring tides) when the moon and sun are
working together and lowest (neap tides) when the sun and moon
are at right angles to each other.
- Many thousands of plants and animals live on the land, and many
thousands more live in the sea. Only a small number of creatures
can live in the coastal zone where the environment changes from
land to sea twice a day.
- Animals that live in the intertidal zone time their lives to the
tides. They continue to behave as if they can feel the tides even
when they are put into an aquarium far from the sea were there
are no tides. Birds, fish, oysters, sea shells, starfish, crabs
living on the sea shore know all about tidal cycles.
- The edge of the sea is also important for people. People came
to New Zealand on boats. To get on and off the boats, they need
places where the coast was protected from waves and deep near
the shore. These places are called harbours. All of New Zealand's
cities were built where they are because of the harbours.
- Beaches and rocky coastlines also attract people for recreation
and fishing. 85% of all the people in New Zealand live in cities
near to the coast and nobody lives very far from it.
- Harbours are special to wildlife because the protected waters
are where many sea creatures live when they are very young. The
water in harbours is rich in food and has many places for small
sea creatures to hide. The food comes from the many plants that
live on the land, from the soil, and animals that live in the
edges of the rivers and shallow wetlands.
- Look at a watershed on a map and compare this to the branches
and roots of a tree. Both are branched again and again until there
are very small branches. In These branches are like fingers reaching
out to gather food and minerals from the land. This branching
pattern is very common in nature where materials are carried from
one system to another. The lungs, which exchange gasses between
the air and the blood are also branched the same way. Blood vessels
that carry food and wastes to and from the cells are branched
the same way.
- People, farm animals, and industry produce waste products
and these are sometimes washed into the water by heavy rains or
dumped into the water through pipes. Often these wastes are contaminated
with molecules that are poisonous to life. These wastes stop natural
cycles, often killing the eggs or very young sea creatures in
the estuaries and harbours.
- Other wastes, such as sewage, may contain good nutrients, but
they are put into the water too fast for the natural cycles to
process. This harms the natural cycles by overloading them. Bacteria
and other disease organisms may become very numerous and cause
more sensitive creatures to die.
- Other wastes, like plastic bags and fishing rubbish,
plug up the natural cycles and tangle sea creatures. Whales have
died from swallowing plastic bags.
- People also damage delicate natural cycles by filling in wetlands.
More than 95% of New Zealand's wetlands have been filled in. Other
areas are destroyed by dredging or by being smothered in mud eroded
from the land. Loss of these valuable biological filters introduces
dangerous silt, toxins, and excessive nutrients into the marine
- Sally Carson, Gael Arnold,
Bob Drey, and other sea keepers, understand
that people can stop harming this delicate coastal area if they
are more careful about what they do. To be more careful, people
have to learn how they harm the sea and then work out ways to
help, and not hurt, the natural cycles.
Resources to use
Microsoft CD The Magic School Bus Explores the Ocean
Microsoft CD Oceans
Starters and Strategies Magazine. No. 20 Feb. 1996. p. 32-33.
A guide to New Zealand Seashore Dave Gunson
Between the Tides, Mike Bradstock, Reed Methuen,
Margins of the Sea, Exploring New Zealand's Coastlines.
Professor John Morton. 1985.
Nature Watching on the Beach John Walsby, Wilson
and Horton, 144pp.
New Zealand Sea Shores by Professor John Morton
is a classic reference book on the sea life of New Zealand's coastal
areas, with information on the condition of the sea shore around
the coastline dating back over twenty years.
Seashore Life of New Zealand by Erick Heath and
R.K. Dell. Reed Publishers
Seashore Secrets. by Sally Carson 1995
Aerial photographs and maps of a study area.
Field identification guides for shells, sea birds, algae, and
other shore creatures.