You have no doubt
started hearing some 'loony' fringe elements of the conservation movement
arguing that:
-
High fuel loads have
no bearing on bush fire frequency and intensity.
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That fuel reduction
burning is damaging to all forests, makes them drier and more fire prone.
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That it is land
developers pushing for more fuel reduction burning in order to
make it more cost effective for them to convert forests to urban
developments.
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That we should be
irrigating dry forests, on a large scale, in order to convert
them to wet sclerophyll forests and rainforests thus making them
less fire prone in the long term.
Such elements often
have no formal education in science or conservation land
management, have never lived in the bush, do not live in the
bush and/or have never been employed in the conservation and land
management industry. They fail to recognize that Australian
forests are not uniform and that therefore any particular management
practice and fire regime cannot be applied across the board. Australian
ecosystems have been categorised into a series of EVCs or Ecological
Vegetation Class such as 'wet sclerophyll forest', 'cool temperate rainforest',
'warm temperate rainforest', 'wet heathland', 'heathy dry forest',
'woodland', 'dry heath land', 'plains grassland' and many others. These
EVCs are defined by the types of plants present, the dominant
species, the density of the tree canopy and the of the trees
themselves, the topography, the
geology and the rainfall etc. The required
controlled burn regimes vary from regular in dry forests, where fire
enhances biodiversity, to not at
all in temperate rainforests, where fire destroys biodiversity. The environmental weeds
present at a specific site, accessibility of the terrain, the size
of the reserve and specific fauna species present at a site can also heavily influence what
management practices and controlled burn regimes are appropriate. These
fringe elements also often refuse to accept that even in one
particular forest site there are often more than one forest EVC in
different niches within the site. E.G. 'Wet sclerophyll forest' or
'warm temperate rainforest' may occupy moist gullies and valleys
while a mixture of 'heathy sclerophyll forest' and 'grassy
sclerophyll forest' may occupy the exposed ridges and hill tops.
So even within one particular forest
site different management practices and fire regimes are required
for different parts of the forest. Suffice
it to say that those of us in the mainstream conservation movement
do not support the often ludicrous pronouncements from these fringe
elements, e.g. particularly that controlled
burning should cease in all forests, even though there is difference of
opinion among conservationists and scientists alike as to frequency, extent and timing,
of prescribed burns. And any
prescribed burning programs
must take into consideration the considerable amount of land
clearing that has occurred since European settlement. It may
sometimes be difficult to reconcile the expectations of the general
public with specific conservation goals of a particular site. But
there is almost universal
acceptance within the conservation mainstream that fire is an
important part of most Australian ecosystems and therefore a
necessary management tool for both biodiversity and public safety. Here
are a few important points regarding the role of fire in Australian
ecosystems:
-
Australia's climate
has been gradually drying for the past 10,000 years or so as our
continent has drifted towards the tropics. It now straddles the
'desert latitudes'.
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If you look at any map of the globe you will
notice that the central Australian deserts are matched by
similar deserts, within the same latitudes, in southern Africa and
South America.
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The point of this is
that there are far bigger forces of nature at play, now
including global warming, than forest management practices that are influencing
Australia's climate and therefore the character
of our forests and woodlands.
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It is this gradual
drying, due to continental drift, that is largely responsible
for most of Australia's forests being dry, dominated by fire loving and promoting
plants like Eucalypts and very susceptible to bushfires.
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We have a great deal
to learn from Aboriginals who still have knowledge of
traditional ecosystem management.
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For thousands of years Aborigines carried out 'fire stick
farming' with the express purpose of preventing the thickening
of scrubby undergrowth in forests.
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What they ended up
doing was to smooth out the wide fluctuations around the
equilibrium, between fuel loads and resulting fires, that
existed in Australian ecosystems prior to their ancestors
arriving.
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The fires they lit
were nearly always very limited in extent and intensity and
resulted in an intricate patchwork of burned bush and
bush in various stages of regeneration.
-
When a new fire went
through, nearby there were always previously burnt patches for
people and wildlife to escape into during the fire and regenerated patches
where they could live and obtain food and water after the fire.
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This resulted in a
very stable ecosystem that lasted for tens of thousands of years
and allowed our incredible plant and animal diversity to evolve.
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This biodiversity is
critically dependant on the relatively low intensity and small
scale fires that the Aborigines used to light.
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We are now
custodians of that biodiversity and few Australians would
disagree with our obligation to protect it for prosperity.
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However we cannot
protect our biodiversity if we are going to fundamentally change
the Aboriginal land management practice that gave rise to it in
the first place.
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The enormously hot
wildfires that we have seen recently are extremely damaging to the
biodiversity of our forests if they are allowed to occur too
frequently, i.e. every 10 to 15 years as has been the case since
1939 at least.
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With wildfires like
this the bush is burned for many miles around, there are no refuges for animals and
people to escape to and there are no refuges for wildlife to
obtain food and water in the weeks and months after the fire.
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With the
introduction of thousands of environmental weeds by Europeans,
such vast areas of bush can become heavily infested with weeds
before the native plants have a chance to regenerate and it is
difficult and expensive to carry out weed control over large
areas.
In his book "The
Future Eaters" renowned palaeontologist and Australian of the
Year Tim Flannery details an interesting and plausible theory as to
why Australia become dominated by fire promoting plants like
Eucalypts. See below. Top
Mud cores have been taken from
various locations around Australia like the continental shelf of the
QLD coast, lake George and a volcanic lake on the Atherton table
land in QLD. The further towards the bottom of the mud core you go
the further back in time that those particular sediments were
deposited. The mud also contains the pollen grains of plants and so,
by examining the types of pollen present in different sediment
layers, you can infer the dominant plant genera that were growing in
Australia at the time. The
pollen of all plant species within a particularly genera are always
very similar and distinctive. For example the pollen of all
Eucalypts is very similar, even those Eucalypt species that have
long since become extinct. The
evidence points to the fact that much of Australia was blanketed in
various types of rainforest up until quite recently. The precise
time is under debate within the scientific community and estimates
vary from 100,000 years ago to as little as 38,000 years ago.
Familiar 'temperate rainforest' blanketed the wetter niches of the
Australian landscape but the majority of it, including the dry
western flanks of the Great Dividing Range, was blanketed in a very
unusual type of rainforest. It is
called 'dry rainforest' and it was dominated by fire sensitive
conifers from the Araucaria genus. 'Dry rainforest' looks more or
less the same as a 'temperate rainforest' except that the component species were able to survive
in much drier conditions. Eucalypts were present in Australia,
probably in fire prone heath lands, but were far less prevalent than
they are at present. The
only remaining tiny remnants of these 'dry rainforests' are found in
the midst of Brigalow Scrubs
on the western slopes of the Great
Dividing Range. Brigalow Scrubs are extraordinarily resistant to fire
and in the midst of these scrubs small patches of 'dry rainforest',
as well as other very unusual and fire sensitive plant communities, are protected from bushfire that ravage the region from time to
time. Sadly Brigalow scrubs themselves are extremely endangered due
to past land clearing to make way wheat crops. At the time that much
of Australia was blanketed in rainforest, both temperate and dry,
Australia's megafauna was at its zenith. Herds of Diprotodons and
short faced kangaroos roamed the plains and forests and they were
hunted by Tasmanian tigers, marsupial lions and even carnivorous
Kangaroos. There were also familiar Eastern Grey Kangaroos but back
then they were about 30% larger than today's Eastern Grey Kangaroos
and stood about 3 metres tall. Then
abruptly, at some point between 100,000 years ago and 38,000 year
ago, the number of
microscopic charcoal particles present in the sediments of many of the
core samples dramatically
increases. There after Eucalypts become by far the dominant
plants along the east coast of Australia. At the same time or soon
after Australia's megafauna became extinct and mangrove pollen makes
a sudden appearance in the sediments. Mangroves thrive in tidal mud flats produced by
accumulated sediments eroded from hills and mountains and
transported by rivers. What
happened in Australia at this time to cause the extinction of our
megafauna and such a dramatic and rapid shift in Australia's flora? It
is widely accepted that Aborigines have been present in
Australia for at least 40,000 years. But many scientists believe it
is likely that they arrived in
Australia perhaps as much as 60,000 years ago, although palaeontological
evidence is very rare and inconclusive. Either way it is a
reasonable proposition that the the arrival of Aborigines in
Australia, the extinction of our megafauna and the dramatic shift in
Australia's ecosystems were not coincidental. In
many regions of the world there is sufficient palaeontological
evidence to suggest that the much of the megafauna of those regions
became extinct soon after the arrival of humans beings. In short the
number of human beings increased rapidly due to the abundant supply
of meat, resulting in over exploitation of the megafauna to feed the
growing number of mouths and eventual extinction of the megafauna.
This often happened in a very short space of time, geologically
speaking, perhaps as little as 200 years in some cases. The
most recent example of megafauna extinction, for which there is
abundant archaeological evidence, is the extinction of the Moa in
New Zealand brought about by the Maori. There are sites in New
Zealand that consist of tens of acres covered in the bones of tens
of thousands of Moa. There are ancient ovens that contain cooked Moa
haunches that the Maoris of the time never even bothered to open.
The Maoris only ate the haunches and left the other parts to rot. So
when Moa meat was abundant the Maoris were incredibly wasteful. When
the British arrived Maori civilisation was in terminal decline with
chronic food shortages and a widespread culture of theft, violence, cannibalism
and warfare. Is this sounding vaguely familiar in the context of contemporary
western economic civilisation? We seem to be experiencing increasing
crime and ethnic tension within our societies along with increasing
warfare between neighbouring nations and between nations and their
own ethnic minorities, often over resources like land and water? In
Africa large herds of large herbivores consume enormous quantities
of vegetation and convert it to dung. The dung is quickly
incorporated into the soil, along with abundant plant nutrients, by
hordes of dung beetles. This is a closed and very productive
ecological system where nutrients are cycled very rapidly and little
if any nutrients are lost from the system. This is much like a
modern economic system, with trade barriers, where money is
continually cycled through the economy and makes it vibrant and
productive. If the large
herbivores are removed then vegetation quickly builds up and grass
lands give way to woodlands and scrubs and then forests. Trees and
shrubs continually shed their leaves and branches while dry uneaten
grasses foliage continually builds up. Sooner or later lightening
will spark a fire that rapidly gets out of control with so much fuel
on the ground. Fire replaces large herbivores as the consumer of
vegetation, however it is far less efficient because so much of the
nutrients in the plant matter are lost in the smoke that drifts
away. Could it be that the
the ancestors of Aborigines arrived in Australia about 100,000 years
ago and quickly hunted the megafauna into extinction? Tim Flannery
thinks this is very likely. If
so then with the megafauna gone there was nothing to consume the
vegetation which kept growing until vast quantities of fuel built
up. When lightening ignited fires these would have spread rapidly
out of control over vast areas with so much accumulated fuel. The
regular fires would have driven the fire sensitive 'dry rainforest'
plants into rapid decline and opened vast new opportunities for the
fire loving Eucalypts which then proliferated equally rapidly. Could
the sudden appearance of mangroves indicate that, at the time that
massive wildfires were ravaging the ancient rainforests and before
Eucalypts had dominated the landscape, there was an episode of
massive erosion on the exposed eastern flanks and foot hills of the
Great Dividing Range resulting in massive quantities of sediments
being deposited in the river estuaries? Is this why Australia's top
soils are generally so very thin? The
nutrient value of Eucalypt foliage is very much less than the
foliage of 'dry rainforest' plants and there were only a handful of
marsupial herbivores, the ancestors of possums and koalas, that
could eat it. The closed and efficient nutrient cycle of Australian
ecosystem was broken to be replaced by a very much less efficient
one where fire was the key to releasing the sparse nutrients held in
Eucalypt foliage. But nutrients were continually leaching out of the
Australian ecosystem with the smoke of the fires, resulting in soils
becoming ever poorer. Any chance that 'dry rainforests' could make a
major come back were lost long ago. The
ancestors of Aborigines would have been in dire trouble. They would
have seen their traditional food sources going
up in smoke with the dry rainforests at an alarming rate to be
replaced by inedible Eucalypts. The megafauna was extinct or almost
so, with only
small to medium size game remaining. But that would have been driven
away from their homelands as vast areas of it burned to ash. Over
time the Aborigines realised that they could control the fire / fuel
build up cycle by burning the bush at safe times of the year before
fuel loads built up to dangerous levels. In so doing it suppressed
the growth of forest and scrub and promoted the growth of herb rich
grasslands that in turn attracted small to medium herbivores, like
kangaroos and wallabies, that were able to proliferate to a greater
extent than they otherwise would have. The intimate relationship
between our flora and fauna and fire had begun and eventually gave
rise to the incredible biodiversity that we are now custodians of. The
Aborigines learned the lessens of unsustainable growth and
consumption well and transformed their culture into one that as
eminently sustainable and has lasted, largely unchanged, for at
least 40,000 years. The future eaters had become experts in
extracting a living from Australian ecosystems while preserving and
enhancing biodiversity. Johnny come lately
Europeans had the poor grace to regard Aborigines as being primitive
and inferior.
Top
According to Chris McLean from the Centre for the
Risk Management of Bushfires at the University of Wollongong: "There
are a number of studies that have occurred throughout Australia on
fauna recovery post fire yet unfortunately control impact studies
(where monitoring had occurred before and after wildfire) are a
little scarce. One of the most famous studies have occurred in the
heathland of Nadgee Nature Reserve since the early 1970s by Dan
Lunney, Harry Recher and other associates with monitoring mainly
concentrating on small mammal populations. The area experienced a
high severity wildfire in 1972 (2 years into the study) and a low
severity wildfire in 1980 with no fires since. Small mammals have
been continuously sampled on the site since 1972 and their
population trends are summarised by Recher et al in the current
issue of Wildlife Research. While undertaking his PhD at the Myall
Lakes in northern NSW, Barry Fox's study site experienced a wildfire
thus presenting a nice opportunity to document small mammal recovery
post fire (documented in papers in the early 1980s with one in
Ecology in 1982 if my memory serves rightly). The conclusion to
these studies from infrequent high intensity wildfires in heathlands
(ie 'flammable environments') is that populations of common species
such as Brown Antechinus/ Agile Antechinus and Bush Rat/ Swamp
Rat peak at around 7 years post fire and decline thereafter.
Having said that several 'threatened' rodent species (New Holland
Mouse and Eastern Chestnut Mouse) reach a maximum population density
within 2-3 years post fire and decline thereafter and are probably
threatened by infrequent fire. Several reviews on small mammal fire
ecology have been completed, for example Liz Sutherland and Chris
Dickman in Wildlife Research around 1999/00 but I would also have a
look at Peter Catling's critisism/ critique of frequent hazard
reduction burning in the 1st edition of The Conservation of
Australia's Forest Fauna (ed D Lunney, published by the RZS NSW).
More importantly I suppose for the victorian
Mountain Ash/ Alpine Ash/ Messmate forests and fire recovery a great
deal of work has documented the requirement of these communities of
infrequent high severity fire (ie crown fire) to regeneration (ie to
stop them becoming rainforests). Dave Ashton completed a PhD around
Kinglake in around 1964 and Malcolm Gill (CSIRO) has worked
extensively on the ecology of Alpine Ash. Anyway back to fauna
responses. Brendan Mackey, David Lindenmayer and associates
published a book by CSIRO publishing in around 2001/02 called
Wildlife, fire and future climate based on fire ecology of Mountain
Ash. This book might be out of print but good uni and TAFE libraries
should have a copy. It contains details of modelling of mountain ash
hollow dynamics post fire and lots on the leadbeater's possum, a bit
of a conservation paradigm as it requires hollows but also Acacia in
the understorey thus fire events are good but also bad. There have
been a number of studies in Mountain Ash and other recently burnt
vegetation types, for example one in Wildlife Research by van der
Ree and Loyn (from around 2000) that compared Greater Glider and
Small Eared Possum abundance among sites last burned in 1939 in
comparison to those last burned in 1983. There were more Greater
Gliders in 1939 sites yet due to a lack of fire severity work I
wouldnt conclude anything further on it.
So I guess in conclusion with fires there are
winners and their are losers. Certain species are sensitive to
frequent fire while others relish frequent fire. Unfortunately we
cant cater to all species with single fire regimes and at best we
can probably only cater to species that are easiest to monitor,
represent the greatest ecological importance or are flagship species
(ie cute and cuddly)." I would add to this, that
as long we don't put all or prescribed burning eggs in the one
basket and implement a large variety of prescribed burning regimes
in different regions and different areas within given regions, then
we stand a reasonable chance of preserving even the non-flagship
elements of our fauna in the long term. Top
After you have worked in the bush
for a year or more you start to notice a fundamental difference
between they way exotic environmental and noxious weeds respond to
rainfall and the way in which most native plant species respond. The
seeds of all environmental and noxious weeds germinate rapidly
with the least little bit of rainfall, grow very quickly and then,
once the rainfall dries up, the weeds rapidly dry out and leave
dense thickets of very dry vegetation. Most native plants show
virtually no response to brief and transient showers and their seeds
will only germinate when there is sustained and substantial
rainfall. This is why it takes a lot of time and effort to restore
infested remnant bushland. Consequently
intact native bush land is often quite open with surprisingly little
ground storey vegetation while weed infested native bushland is
dense and often impenetrable. So it should be fairly obvious that
weeds make a significant contribution to the propagation of
bushfires at ground level. You
also notice in weed infested bushland, that when you remove large
Eucalpyts, you often get a rapid boom in weed growth. More sunlight
reaches the ground and the Eucalypts roots no longer steal water and
nutrients from the weeds. So
the frenzy of tree removal that is currently taking place on the
urban fringes of Melbourne in response to the 2008 bushfires may
actually contribute to making the bushfires worse in two ways. By
increasing their intensity by improving weed growth and thus the
density of the fuel load at ground level. And by increasing their
speed of bushfires by removing the only thing that can slow down
strong winds - large trees. So
I would recommend that, if you are participating in this tree
removal frenzy, you take a step back and think a little more
carefully about the possible unintended consequences of what you are
doing. Top
There is a great deal of paranoia
about the use of herbicides these days but few people really
understand herbicides beyond this scary sounding word. So
let's look more closely at a useful herbicide that I use from time
to time on the likes of soursob and wastsonia.
The chemcial name is metasulfuron methyl and it is sold under such
product names as Esteem and Brushoff. It belongs to the sulfonylurea
group of organic compounds. Again its sounds scary doesn't it, but
let's look beyond the scary name. Let's take the 'urea' part of the
name.
The molecular formula of urea/carbamide is:
Again it sounds scary doesn't it.
Well all mammals, including humans, excrete excess nitrogen,
resulting from the break down of proteins, in the form of urea in
our urine.
Here is the molecular formula of metasulfuron methyl:
You can see the urea molecule in the middle flanked by the molecules
of two benzene derivatives, represented by the hexagonal
arrangements of atoms.
The sulfonyl bit is represented by the S (sulphur atom) with two
O's(oxygen atoms) attached to it via the double lines
Again it might seem very scary to those who have not studied organic
chemistry but what if I was to tell you that many of the drugs used
to treat type 2 diabetes also belong to the sulfonylurea family of
organic compounds? Or that sulfonylureas are very closely related to
the 'sulfa antiobiotics' that are used routinely to treat
infections.
Ecological Effects
--------------------
Metsulfuron-methyl has a low toxicity to birds,
aquatic organisms (including fish), bees, and
earthworms.
Environmental Fate
-----------------------
The breakdown of metsulfuron-methyl in soils is
largely dependent on soil temperature, moisture
content, and pH.(acidity / alkalinity) The chemical
will degrade faster under acidic conditions, and in
soils with higher moisture content and higher
temperature.
The chemical has a higher mobility potential in
alkaline soils, due to its higher solubility.
Metsulfuron-methyl is stable to photolysis, but will break down in
ultraviolet light. It is also stable to
hydrolysis in neutral and alkaline conditions.
Metsulfuron-methyl is rapidly taken up by plants at
the roots and on foliage. The chemical is
translocated throughout the plant, but is not
persistent. In tolerant plants, it is broken down to
non-herbicidal products.
Human Toxicity
-----------------
Metsulfuron-methyl has very low toxicity in
mammals. Systemic poisoning is unlikely unless
large quantities have been ingested. The chemical
is broken down quickly and eliminated from the
body. Based on tests conducted on laboratory
animals, the following may be concluded.
· No adverse effects on reproduction are likely.
· No birth defects are likely.
· Metsulforon-methyl is not carcinogenic.
· It is neither mutagenic nor genotoxic
· It is a moderate eye irritant.
Metsulfuron-methyl is not classified as a poison.
Top
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