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All
of the biodiversity of our forest ecosystems evolved
over the millenia in old growth forest environments.
Over
a relatively short period of less than 200 years,
those old growth forest habitats have been destroyed
or fragmented and degraded by clearing, road construction,
clearfelling, prescribed burning and mining. Along
with these direct impacts have come other threatening
processes e.g diseases such as dieback; introduced
predators such as foxes; salinity; and climate change.
As old growth forest habitats are lost, degraded
and exposed to various threatening processes, more
and more species will become vulnerable to extinction.
1. Is
extinction a problem in our forests?
"Several
recent reports in the Australian electronic and print
media have suggested that there have been no extinctions
in native forest environments and, as a result, implied
that forestry operations have had no impacts on biodiversity...However,
the contention that there has been an absence of
impact warrants closer scrutiny from ecologists for
a range of important reasons...There is evidence
of localised extinctions of taxa from extensive areas
of timber production forest...Even though a given
species may not be totally extirpated as a result
of logging, its numbers may be so depleted that it
can no longer interact significantly with other species
['functional extinction']...Large declines in species
abundance may have major consequences for key ecosystem
processes...[Studies suggest] the existence of an
'extinction debt' whereby a species may eventually
be lost well after disturbance events or processes
have taken place. Thus it is possible there are long
term effects of current logging operations and that
future losses in forest biodiversity may occur in
response to activities taking place now...Thus, suggestions
that there have been no impacts of [logging] because,
as yet, there may have been no extinctions is an
extremely poor and insensitive measure of the ecological
sustainability of the industry" Dr P. Gibbons and
Dr D.B. Lindenmayer, Institute of Foresters Newsletter,
1997
"...local
extinctions are widespread in the [South West forest]
region, such as the woylie and the numbat from the
Blackwood Plateau...The presumed reason for the disappearance
of the bilby, the burrowing bettong, the rufous and
western bristlebirds, the noisy scrub-bird, the western
whipbird, the ground parrot and the malleefowl, is
the degradation of their habitat through frequent
fires...It is clear none of these species would be
able to survive under present forest management conditions
...Many endangered species, such as the chuditch,
the numbat, the woylie, the tammar wallaby, and the
yellow-bellied frog, are likely to be directly affected
by forestry operations. Other species which were
relatively widespread in the region have suffered
significant decline and are now uncommon, such as
the brushtail possum, brush wallaby, quokka, water
rat, brush-tailed phascogale, red-tailed black cockatoo
and Baudin's white-tailed cockatoo." Dr Jean-Paul
Orsini, Threatened Species Network, 1994
"The
Inquiry found that logging is likely to increase
the risk of extinction of some species...The National
Association of Forest Industries cited the absence
of recorded extinctions as evidence that proper forest
management contributes little risk. This observation
should be treated with caution for several reasons:
forest ecosystems contain many different types of
organisms and very few have been monitored for any
length of time; the absence of recorded extinctions
is not in itself evidence that there have been no
extinctions; the absence of recorded extinctions
does not mean that future extinction risk is low,
especially under changing environmental and management
conditions; the conversion of native production forests
from mostly old growth to mostly regrowth is continuing
and the effect on old growth-dependent species cannot
yet be determined." The Resource Assessment Commission,
Forest and Timber Industry Inquiry Final Report,
1992
2. Hollow-dependent
species
"Wardell-Johnson
started research on the age to formation, and cause
of hollow formation in karri and marri trees but
it was discontinued...the youngest karri tree found
to include hollows was 168 years...The timing and
cause of formation of hollows in karri, marri and
jarrah trees requires research commitment as preliminary
work suggests a much longer period required in the
formation of such hollows than previously thought." Wardell-Johnson
and Christensen (CALM), (uncensored draft), 1992
"There
is no baseline information on the natural occurrence
and use of hollows by vertebrates in mature forests...The
(CALM) figure of '15 habitat trees per five hectares'
comes from a single study of the requirements of
a single species...It takes no account of the other
19 mammals and 31 bird species [51 species total]
that require hollows for breeding and shelter in
the south west forests." Report on CALM's proposed
forest management plans by the Technical Advisory
Panel to the Environment Protection Authority, 1992.
"Suitable
hollows are defined by depth, with deeper hollows
being used more frequently. Suitable hollows first
develop in jarrah trees at about 300 years of age
and in marri trees at about 200 years. The average
age of trees inhabited by possums was estimated at
about 500 years for jarrah and 400 years for marri." Wardell-Johnson
(CALM) and Nichols, 1992
"Clearfelling
for woodchipping removes the old trees and, though
regenerating forest will provide sufficient food,
current rotation periods will not allow time for
hollows suitable for nesting to develop... The presumed
longevity of the species [Baudin's Black Cockatoo]
may, as yet, be masking insufficient recruitment
rates." The Royal Australasian Ornithologists Union,
1992
"Some
of the subspecies' [Red-tailed Black Cockatoo] habitat
has been cleared for agriculture but the main threat
may be from forestry operations. In the woodchipping
licence area between Bridgetown and Walpole, which
includes about one quarter of the subspecies range,
management involves a rotation period that will not
leave sufficient time for nesting hollows to form." The
Royal Australasian Ornithologists Union, 1992
"The
lowest average estimated age of nest trees recorded
for any of the parrot species was 275 years, and
446 years for the cockatoo species. In view of current
timber
production strategies and management policies for
remnants of native vegetation there is a real possibility
that nest hollows may be in limited supply in some
areas in the near future. To ensure a continued supply
of nest hollows for parrots it will be necessary
to modify existing timber production strategies in
forests..." P.R. Mawson and J.L. Long, study published
in EMU, Royal Australasian Ornithologists Union,
1994
"A
major conclusion from our study was that the array
of issues associated with the retention of trees
with hollows within Australian wood production eucalypt
forests are considerably more complex than presently
appreciated by the majority of forest and wildlife
managers. Indeed it appears likely that most existing
prescriptions for the retention of trees with hollows
in logged sites are inadequate and may not either;
(1) ensure the long term perpetual supply of a range
of types of hollow trees and/or (2) provide the necessary
habitat conditions to support viable populations
of some species of hollow-dependent fauna" Dr P.
Gibbons and Dr D.B. Lindenmayer, Forest Management
and the retention of trees for the conservation of
hollow-dependent fauna, 1995
"...it
seems clear to me that the current rate of harvest
on jarrah forests cannot be sustained for long at
its current level...A similar management philosophy
was once imposed on the forests of the southern U.S.
and the Pacific Northwest of the U.S...the long term
persistence of several species of forest fauna fell
into question, despite policies and laws that spoke
of multiple use, sustainable management, and wildlife
protection...non-timber values associated with large
trees [in the jarrah forest] are not being provided
on these lands". William McComb, Professor of Forest
Science, Oregon State University, 1994
"Felling
and burning produce an inhospitable habitat within
the coupe with the result that fauna within the area
are removed...Very few animals are able to live on
bare burnt areas and few of those species that lived
there formerly are able to adapt by moving to nearby
uncut forest areas...many fauna species will only
be present in 10% of their former numbers existing
entirely within the uncut areas." WA Forest Department,
Woodchip EIS, 1973
NOTE: This
paper deals mainly with larger vertebrate fauna.
Many other aspects of biodiversity e.g. flora, invertebrates,
fungi, are likely to be similarly threatened.
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