There has been a bit written at this site about the importance of burning landscapes including comment from David Ward in WA that:
“I have recently developed geometric evidence that frequent burning is the only (repeat only), way to maintain a reasonably fine grained fire mosaic, with small, mild, and controllable fires; a rich diversity of habitat for plants and animals; and protection of small fire refuges for that minority of plants and animals which are not adapted to frequent fire. Aborigines clearly knew, and still, in some parts, know this. Anyone who does not understand should go and talk to an Aboriginal Elder.
“It can be demonstrated, with geometric certainty, that any deliberate long fire exclusion over large areas, such as a National Park, will lead inevitably (repeat inevitably) to large fierce fires, and a coarser mosaic, with little diversity of food and shelter for animals. Small refuges, important for some rare plants and animals, will be destroyed by the ferocity of the fires.”
I have just discovered Christine Jones’ website at http://www.amazingcarbon.com/ courtesy of Graham Finlayson.
Jones suggests that regular burning is extremely detrimental to soft forms of native ground cover and encourages a dominance of relatively unpalatable grasses, removes surface litter leaving the soil unprotected, reduces potential for nutrient cycling, reduce water-holding capacity and degrade soil structure. … concluding that “fire is a tool which should be used cautiously and infrequently”.
Jones suggests that the recruitment of productive native legumes and grasses is favoured by mulching which is destroyed by regular burning.
Jones promotes grazing on the basis that “The open, park-like appearance of many areas at the time of European settlement has often been attributed to indigenous burning regimes. More recent evidence suggests that the healthy grasslands and friable soils described by the first settlers were more likely to have reflected the high abundance of small native mammals, such as bettongs and potoroos most of which are now locally extinct … with the loss of the regenerative effects of small native mammals in Australia since European settlement, managed grazing is now arguably the only natural means by which grasslands can be ‘improved’ in a holitistic way.”
The above is my summary of page 7 and 8 of http://www.lwa.gov.au/downloads/general_doc/46_sti1%20final%20report.pdf, titled ‘Recognise, Relate, Innovate’ by Jones – at the same website.
Are Jones and Ward talking about different landscapes?
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Thanks for drawing this to my attention Jennifer. I found the website a bit slow and painful to read, but perhaps it’s time I moved to broadband.
Christine says that “The recruitment of productive native legumes and grasses is favoured by a mulched soil”.
The cover photo appears to be Kangaroo Grass (Themeda australis). This grass grows around the Indian Ocean, from South Africa (Rooi Gras to the 1830 Voortrekkers) to Australia. It is one of the most nutritious of native grasses, and has a definite need for frequent burning. Left unburnt for ten years or so, it smothers under its own thatch – a bit like grasstrees, which cannot shed their leaves, and can only lose them by fire. Lesotho was once famous for its Rooi Gras pastures, due to burning by the Basotho people. Pastures of the same grass are (or were) maintained by frequent fire in Sri Lanka, Timor, Papua New Guinea, and elswhere.
Early explorers in Australia mentioned large areas of Kangaroo Grass, from Tasmania to North Western Australia. This single species is strong evidence of frequent burning in the past, and it has been suggested that it was spread south from its tropical origin by human activities.
Christine Jones says that “hot burns remove surface litter, leaving the soil unprotected…”. This is absolutely true, and was illustrated by the silt dumped into NSW dams after the recent hot fires there. The point Christine misses, as do many people with little understanding of fire behaviour, is that “hot” fires can only occur after long fire exclusion and fuel buildup. Where burning is frequent, and fuels light, fires are much milder, and patchier, leaving refuges for plants and animals. The big hot fires due to long fire exclusion destroy these refuges, leaving a moonscape, littered with animal corpses. We have had several such fires over the past few years in WA. They kill “old growth” trees. How did these trees survive for 200 years or more, given that lightning fires would have occurred, and there was no fire brigade then?
The hypothesis that abundant small mammals turn over the soil is true. I have given up trying to grow a lawn, because bandicoots (common and unendangered in Perth Hills) regularly rootle it up. However, I doubt if the whole jarrah forest of SW Australia was like a pig paddock before European settlement. Nyoongars hunted and ate bandicoots, and other mammals, keeping their numbers in check. Dingoes did similarly. This does not seem to have occurred to those who fence off bits of bush and reintroduce only the nice cuddly animals, which, in the absence of predators, then breed up and proceed to ravage the vegetation. Remember Yellowstone Park and the wolves?
A few years ago in WA, such a reserve was burnt in a fierce fire, due to long fire exclusion in the surrounding bush. Small mammal corpses were piled up against the fence. Not intelligent conservation.
I forgot to say that, in WA at least, legumes and native grasses are mostly (all?) germinated best by smoke, which, oddly enough, comes from fires.
Also, I accept that grazing has an important interaction with fire in determining vegetation composition and structure. In Africa, there is a well known sequence of herbivores (different teeth) moving into burnt country, once the grass has resprouted. The herbivores modify the potential fuel for subsequent fires, but do not prevent them. To do so would rob the herbivores of fresh post-fire green pick. Tricky, that old Nature, hey what?
P.S. Over a century ago, a severe drought in India killed many cows. The next year, there were fiercer fires than usual, due to the ungrazed grass. Are you listening, Tim Flannery?
On this site, there seems to be less interest in bushfire threat than in climate change. Is there a general inverse relationship between the amount of hot air produced, and the reality of the threat?
Apologies cos I can’t format these comments. How do you do it?
There’s a lot of confusion about changes in fire regimes and vegetation since European settlement. Grazing in open forests and woodlands helped to conserve some ecosystems after we interfered with fire regimes. Excluding fire and/or grazing causes fire problems and tree decline.
Australia is naturally arid and infertile. To conserve natural ecosytems you have to keep it like that. If you make it lush and green, some native species (e.g. eucalypts) will decline while others will flourish and become pests (e.g. psyllids, Christmas beetles, stick insects, mistletoes, noisy miners, bellbirds, koalas).
Eucalypts evolved while the environment was becoming increasingly arid and infertile. There were frequent low intensity fires, ignited by lightning and Aboriginal people, that prevented accumulation of ‘mulch’, proliferation of perennial understoreys, cooling and dampening of the microclimate under the canopy and acceleration of nutrient cycling processes.
Since European settlement, fire suppression in forests has initiated a vicious circle of: accumulating litter and organic matter on the forest floor, accumulating nitrogen and moisture in the topsoil, increasingly dense understoreys or ground layers, increased cycling of nitrogen in soils and vegetation, increasing shade at ground level, increasing nitrogen in leaves of trees, increasing rates of leaf fall, increasing organic matter and nutrients in litter and topsoil.
High intensity fires reinforce the changes by stimulating nutrient cycling and understoreys.
Competitors, parasites and diseases of eucalypts flourish with exclusion of fire because the trees are stressed by the changed environment whereas the pests are favoured by the changes in the environment and in the trees. (Stressed trees produce more nutritious sap/leaves etc..)
Human activities have accelerated nitrogen cycling throughout the world and there is increasing recognition that tree decline is associated with
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