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Alpine grazing: does it reduce blazing?

Monday, 2 December 2013  | 

The Victorian Mountain Cattlemen’s Association has called for the re-introduction of cattle grazing in the Victorian Alpine National Park to reduce fire risk, based on their view that ‘alpine grazing reduces blazing’. However, a substantial body of peer-reviewed scientific evidence indicates that alpine grazing does not reduce fire risk.

Detailed studies of the 2003 and 2007 fires in the Victorian Alpine National Park showed that cattle grazing had little or no effect on occurrence and/or severity of fire in the alpine vegetation above treeline, and in the surrounding subalpine woodland and montane forest. Flammability depended largely on vegetation type. For example, the 2003 fires on the Bogong High Plains burnt 87% of closed heathland and 59% of open heathland, but only 13% of grassland; grazing did not reduce the incidence of fire in any of these vegetation types.

Cattle graze selectively and this partly explains why grazing had little effect on the patterns of burning.  On the Bogong High Plains detailed studies have shown that cattle prefer to graze on the grasses and herbs of the more open vegetation types such as grassland and open heathland, and avoid eating the tall shrubs of the closed heathland. Long-term monitoring on the Bogong High Plains for over 50 years has shown that cattle grazing has not reduced the cover of tall shrubs that dominate the most flammable vegetation – closed heathland.

Victoria’s alpine vegetation is resilient to large fires and there is no apparent conservation imperative to mitigate the extent or severity of large fires. Livestock grazing, on the other hand, has well-documented negative impacts on the conservation values of Australia’s rare alpine and subalpine ecosystems. There is therefore no scientific basis to support the re-introduction of cattle grazing to reduce fire risk in Australian alpine and subalpine ecosystems.

Research Entries

Title
Aims
Results
Gibson N., Kirkpatrick J.B. (1989) Effects of cessation of grazing on the grasslands and grassy woodlands of the central plateau, Tasmania. Australian Journal of Botany 37, 55–63.
To assess the variability of the impact of the removal of grazing pressure over an environmental (productivity) gradient (pp. 55).
The response of grassy vegetation to exclusion from grazing was found to be related to a major productivity gradient in the central highlands of Tasmania. All sites showed a trend toward increased structural complexity, a decrease in bare ground and a decrease in species richness when grazing was excluded. However, the effect was much more pronounced at sites of high productivity (pp. 55).
Leonard, S., Kirkpatrick, J., Marsden Smedley, J. (2010) Variation in the effects of vertebrate grazing on fire potential between grassland structural types. Journal of Applied Ecology 47, 876–883.
To "examine the degree to which vertebrate grazing affects fire potential (i.e. the likelihood that given a source of ignition, a fire will sustain and spread) in native grasslands in Tasmania, Australia"' (pp. 877).
In lawn grasslands, grazing markedly reduced fire potential through the removal of plant biomass and by preventing the vegetation escaping into the unpalatable and flammable tussock state. Grazing led to increased fire potential in tussock grasslands where animals selectively removed live shoots, leaving a high proportion of dead fuel (pp. 876).
van Rees H. (1982) The diet of free-ranging cattle on the Bogong High Plains, Victoria. Australian Rangeland Journal 4, 29–33.
To determine the species composition of the diet of free-ranging cattle... to estimate the most important components of the diet… (and) to determine the digestibility and nitrogen content of plants regularly grazed by cattle (pp. 29).
Cattle were seen to eat 26 species of plants, while only 19 species were identified from microscopic examination of cattle faeces. A further 28 species examined in the field showed signs of grazing...Common Poa australis spp. agg. tussocks were of low digestibility and nigrogen content (pp. 29).
Van Rees H., Holmes J.H.G. (1986) The Botanical Composition of the Diet of Free-Ranging Cattle on the Alpine Range in Australia. Journal of Range Management 39, 392–395.
To define quantitatively the diet of cattle in the 3 most common alpine vegetation communities, and to relate the composition of the diet to the availability of plant species in the field (pp. 392).
The steers primarily selected 4 grass species, 3 sedges and 1 rush, 6 forbs and 3 shrub species…. The main species identified in the diet which should be used as indicator species of range condition are: alpine star bush… snow daisy… alpine grevillea…scaly buttons... and soft snow grass (pp. 392).
van Rees H., Hutson G.D. (1983) The behaviour of free-ranging cattle on an alpine range in Australia. Journal of Range Management 36, 1983.
To investigate the behaviour and movements of free-ranging cattle on an Australian Alpine Range.
In both (Cope Creek and Nelse) study areas grazing cattle preferred grassland (pp. 743). Open heathland and closed heathland communities were not actively preferred, and utilisation was similar to availability.
Williams R.J., Wahren C.H.A., Bradstock R.A., Muller W.J. (2006) Does alpine grazing reduce blazing? A landscape test of a widely-held hypothesis. Austral Ecology 31, 925–936.
To evaluate, at a landscap-scale, the effect of livestock grazing on the extent and severity of the 2003 fires in treeless alpine landscapes.
Approximately half of all points were burnt. There was no statistically significant difference between grazed and ungrazed areas in the proportion of points burnt. Fire occurrence was determined primarily by vegetation type, with the proportion burnt being 0.87 for closed-heath, 0.59 for open-heath, and 0.13 for grassland and all snow-patch herbfield points unburnt. In both closed-heath and open-heath, grazing did not significantly lower the severity of fire, as measured by the diameter of burnt twigs. (pp. 925)
Williamson G.J., Murphy B.P., Bowman D.M.J.S. (2013) Cattle grazing does not reduce fire severity in eucalypt forests and woodlands of the Australian Alps, in review.
Determine "whether fire severity in eucalypt forests and woodlands in the alpine bioregion is reduced in areas subject to cattle grazing."
Crown scorch was strongly related to vegetation type but there was no evidence that cattle grazing reduced fire severity.
Wahren C.H.A., Papst W.A., Williams R.J. (1994) Long-term vegetation change in relation to cattle grazing in subalpine grassland and heathland on the Bogong High Plains: an analysis of vegetation records from 1945 to 1994. Australian Journal of Botany 42, 607–639.
To assess the trends in, and impacts of cattle grazing on, both vegetation composition and ground cover in two major subalpine plant communities--grassland and open heathland--within the permanent plots established in the 1940s on the Bogong High Plains' (pp. 607-608)
In... grassland plots, established in 1946, cattle grazing has prevented the large-scale regeneration of a number of tall, palatable forbs and short, palatable shrubs, while in the absence of grazing, the cover of these life forms increased substantially. The amount of bare ground and loose litter was significantly greater on the grazed compared with the ungrazed plot...The current condition of grazed grassland on the Bogong High Plains is interpreted as stable, yet degraded. Improvement in condition will occur in the absence of grazing....There was no evidence that grazing has reduced shrub cover...in open heathland (pp. 607).
Williams R.J., Ashton D.H. (1987) Effects of disturbance and grazing by cattle on the dynamics of heathland and grassland communities on the Bogong High Plains, Victoria. Australian Journal of Botany 35, 413–431.
To examine the factors affecting the establishment of shrubs within both heathland and grassland communities, and to assess the role which grazing by domestic livestock may have in this process (pp. 413).
The establishment of shrub seedlings (of several species) occurs primarily upon bare ground, and is absent where the cover of vegetation or fixed Poa hiemata litter remains intact. The survival of Poa hiemata seedlings on bare ground is low, except where local shelter is afforded. Disturbances which cause bare ground, including domestic cattle activity, can create microsites suitable for the establishment of shrub seedlings. Shrub establishment and development may be inhibited by cattle trampling, and some palatable shrubs... are especially affected (pp. 413).
Camac J.S., Williams R.J., Wahren C.H., Morris W.K., Morgan J.W. (2013) Post-fire regeneration in alpine heathland: Does fire severity matter? Austral Ecology 38, 199–207.
To "examine the effects of variation in fire severity on (alpine) plant diversity and vegetation composition, 5 years after the widespread (alpine) fires of 2003" (pp. 199).
In both heathlands, there were few differences in floristic diversity, cover of dominant species and community composition, across the strong fire severity gradient (pp. 199). In the vast majority of cases, plant community attributes (e.g. diversity, ground cover of dominant species, amount of bare ground) are unaffected by fire severity.
Wahren C.H.A., Papst W.A., Williams R.J. (2001) Early post-fire regeneration in subalpine heathland and grassland in the Victorian Alpine National Park, south-eastern Australia. Austral Ecology 26, 670–679.
To "summarize the early post- fire changes in vegetation and ground cover conditions that have occurred in grassland and heathland on Holmes and Wellington Plains" (pp. 671).
Fire caused a substantial decrease in vegetation cover (to ca. 15%) and an increase in the amount of bare ground (to 70-85%). Post-fire regeneration was relatively rapid. The tussock-forming snow grasses resprouted vigorously following fire, and had flowered prolifically after 1 year. After 2.5 years overall vegetation cover in grassland had increased to ca. 65%, but dense vegetation cover was only ca. 25-35% and bare ground had decreased to ca. 30%. In burnt heathland after 2.5 years, dense vegetation cover was generally <20% and bare ground >50%.
Walsh N.G., McDougall K.L. (2004) Progress in the recovery of the flora of treeless subalpine vegetation in Kosciuszko National Park after the 2003 fires. Cunninghamia 8, 439–452.
To assess the mode and extent of regeneration of plants in treeless subalpine plant communities of Kosciuszko National Park that were burnt in the 2003 alpine fires
Twenty-four species (including 3 exotics) were recorded only in the pre-fire sampling. Fifty species (including 18 exotics) were recorded only in the post-fire sampling. One species, Chenopodium erosum, had not previously been recorded in Kosciuszko National Park, and is believed to be the first native chenopod recorded in alpine vegetation in Australia. There was no significant difference in mean number of species per quadrat between pre-fire and post-fire quadrats. The average number of weeds per quadrat was, however, significantly greater post-fire. Most of this difference was attributable to the significantly greater number of weeds per quadrat in bog vegetation after the fire. (pp. 439).
Williams R.J., Papst W.A., McDougall K.L., Mansergh I.M., Heinze D., Camac J.S., Nash M.A., Morgan J.W., Hoffmann A.A. (2014) Alpine ecosystems. In: Biodiversity and Environmental Change: Monitoring, Challenges and Direction. (Eds: Lindenmayer D, Burns E, Thurgate N, Lowe A) pp 169-214. CSIRO Publishing, Melbourne.
To summarise the nature of environmental change in Australian alpine environments, with particular reference to policy development and implications.
Changes in the balance between shrubs, grasses and forbs in alpine vegetation can be substantial, and depend on interactions between disturbance and species life history. Alpine vegetation of mainland Australia has a strong capacity to regenerate after large fires such as those of 2003. Grazing by domestic livestock does not reduce the incidence or severity of fire in Australian alpine ecosystems.
Williams R.J., Wahren C.H.A., Tolsma A.D., SaneckI G.M., Papst W.A., Myers B.A., McDougall K.L., Heinze D.A., Green K. (2008) Large fires in Australian alpine landscapes: their part in the historical fire regime and their impacts on alpine biodiversity. International Journal of Wildland Fire 17, 793–808.
To explore the ‘disaster–diversity’ hypotheses in the aftermath of the 2003 fires on Australian alpine landscapes (pp. 793). The hypothesis holds that "large arge fires such as the 2003 fires were unnatural, the result of decades of fire exclusion, and consequent fuel build-up, in the foothill, montane and subalpine forests, and a disaster for biodiversity in both the wooded and treeless landscapes" (pp. 794).
Historical and biophysical evidence suggests that in Australian alpine environments, extensive fires occur only in periods of extended regional drought, and when severe local fire weather coincides with multiple ignitions in the surrounding montane forests. Dendrochronological evidence indicates that large fires have occurred approximately every 50–100 years over the past 400 years. Post-fire monitoring of vegetation in grasslands and heathlands indicates that most alpine species regenerate rapidly after fire, with >90% of species present 1 year after fire. Some keystone species in some plant communities, however, had not regenerated after 3 years. The responses of alpine fauna to the 2003 fires were variable. The core habitat (closed heathland) of several vulnerable small mammals was extensively burnt. Some mammals experienced substantial falls in populations, others experienced substantial increases. Unburnt patches of vegetation are critical to faunal recovery from fire. There was, however, no evidence of local extinction (pp. 793).