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Old growth forests are forests
whose natural cycles of growth have not been disturbed by
logging, building roads or clearing. Western Australia's old
growth forests have been growing and evolving naturally for
millions of years.
Other words for old growth forest
are 'original' or 'ancient' forest. A forest is a living system
- ongoing cycles of birth and death, growth and decay. It
may appear as if nothing is changing but countless natural
cycles are at work every day and night. What is unique about
old growth forests is that those cycles have continued uninterrupted
over a very long time.
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"Old Growth Forest
is forest that is ecologically mature and has been subjected
to negligible unnatural disturbance such as logging, roading
and clearing.....in which the upper stratum or overstorey is
in the late mature to over mature growth phase."
(National Forest Policy Statement,
Commonwealth of Australia, 1992).
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OLD
GROWTH KARRI FOREST - SIMON NEVILLE |
An old growth forest is
like a community. It includes big old trees, young trees,
mammals, insects, birds, frogs, rocks, fungi, dead trees,
reptiles and countless other living and non-living things.
In Western Australia all
unlogged forests are old growth. Forests which had single
trees taken out (selectively logged) are still old growth
because there was little disturbance to the structure
of the forest as a whole.
Every part of the old growth
forest ecosystem has
an important role to play in keeping the forest healthy.
The living and non-living parts of the ecosystem interact
with each other so if one part is disturbed then the entire
ecosystem will feel the effect. Even scientists don't
always know what the effects of disturbance will be.
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Ecological services of old growth
forest
Old growth
forest provides many important services which ensure the
ongoing health and stability of the environment. Humans
are part of the environment and our well-being depends
on having a healthy environment. These services are:
- Maintenance
of hydrological (water) cycles
- Climate
regulation
- Soil production
and fertility and protection from erosion
- Nutrient
storage and cycling
- Pollutant
breakdown and absorption
- Potential
source for genetic material for new drugs and food crops
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SIMON
NEVILLE |
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Biodiversity
Old growth forests have a high
level of biodiversity,
which means there are lots of different species of plants and
animals found there. The South West Botanical Province (from
Geraldton to Albany) is one of the world's richest areas of
flowering plants, with approximately 9000 species of which over
70 % are endemic (CALM,
A Nature Conservation Strategy for Western Australia, draft
for public comment, 1992). Scientists are still discovering
previously unknown species. For example, in a study of 20 marri
trees, an average of 443 species of insect were discovered living
on each tree. Many of these had never been recorded by scientists
before. (H.F. Recher, J. D.
Majer & S. Garnesh - 'Eucalypts, arthropods and birds; on
the relation between foliar nutrients and species richness.'
Published in Forest Ecology and Management, 85 (1996) p177-195.)
Old growth forests are made up
of trees of many different ages, sizes and shapes, and their
understorey. This is known
as structural diversity.
For example, big old trees, living and dead, standing or fallen,
with hollows of all different shapes and sizes, provide homes
(habitat) for a wide variety
of species, from cockatoos and possums to mosses and fungi.
Regrowth forests are
made up of trees that are nearly all the same age, and do not
have the structural diversity or variety of habitat found in
old growth forest.
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Threats to biodiversity
- Habitat clearing
(e.g. clearing for farming or vineyards)
- Habitat modification
(e.g. prescribed burning, clearfelling)
- Pollution (e.g.
chemical run-off from agriculture)
- Introduced flora
and fauna (e.g. watsonia, bridal creeper, blackberry, foxes,
cats and wild pigs)
- Diseases (e.g.
dieback in the jarrah forest)
- Global climate
change (e.g. greenhouse effect and ozone depletion)
- Size and distribution
of the human population and the level of consumption of natural
resources
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 "The
Facts About WA's Native Forests" - RTF file |
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