Claimed environmental benefits of feral horses (FAQ)

A common claim by brumby advocates is that alpine grazing by feral horses reduces the likelihood and intensity of bush fires. At first glance this sounds like common sense: shorter grass = less fuel = lower fire risk, right? Wrong – multiple scientific studies of grazing in Australia’s high country dispute that notion. 

Scientific studies
Most studies of grazing in Australia’s high country have focussed on cattle grazing in the Bogong High Plains, Victoria. In this area, there are reliable records of which areas were grazed under government licence and which areas were ungrazed, and when. 

A study^[1] of the bush fires of 2003 tested the ‘grazing reduces blazing’ theory. CSIRO scientists Dick Williams and colleagues surveyed grazed and ungrazed treeless land of the Bogong High Plains before and after the fires. They analysed the proportion and size of burnt twigs at 419 survey points across grazed and ungrazed areas. They found no difference between the grazed and ungrazed areas in terms of the likelihood or severity of the 2003 fires. Instead they found that “fire occurrence was primarily determined by vegetation type” i.e. by whether an area was grassy, heathy or snow-patch herbfield. ‘Closed heath’ sites had the highest likelihood of being burnt.

Their findings are supported by other studies^[2] of the flammability of alpine plants. Their report closes with a clear statement: “The use of livestock grazing in Australian alpine environments as a fire abatement practice is not justified on scientific grounds.”

A second study was conducted by ecologist Grant Williamson from the University of Tasmania and other scientists from the University of Tasmania and the University of Melbourne^[3].  They studied both the 2003 and 2007 summer fires in the Victorian alps using remote sensing and GIS technology to compare crown scorch of grazed and ungrazed forests and woodlands. Thousands of points for both fires comprised the final data set. The scientists found that vegetation type predicted the probability of high severity fires. They found no evidence that grazing reduced the fire severity or occurrence. In fact, they found that fire severity was higher within grazing-licenced areas during the 2003 fires. As an explanation for that, they proposed that sustained grazing changed vegetation type by increasing the proportion of more flammable shrubs within grassland. They referred to an earlier study^[4] of the Bogong High Plains which had found that “Grazing by free-ranging cattle appears to favour the recolonisation of such gaps by shrubs rather than by Poa [grass]”. Grant Williamson concluded that, “Our study does not support the proposition that cattle grazing in the Australian Alps reduces fire severity in eucalypt forests and woodlands.”

From a number of studies on alpine bogs and fens, Professor Geoffrey Hope summarised his conclusions: “The Snowy Mountains … support some of the outstanding examples of sodden vegetation that builds up deep organic soils. These peat soils and their dense vegetation cover are important to the ability of the mountains to intercept rainfall … The result is very clean water, released steadily to streams, and a stable moist environment that is fire resistant … Horses are now reversing this recovery [after cattle grazing ceased] and causing further damage. Examples of … drying peat at risk from fire have been described in all areas of horse occurrence in Kosciuszko national Park. Soft moss hummocks that are key to raised water tables are readily destroyed by trampling …” ^[5]

A summary of the science
The Ecological Society of Australia published an article directly answering the question ‘Alpine grazing: does it reduce blazing?’ From published studies, the authors determined conclusively that ‘strong evidence gathered over many years convincingly shows that cattle grazing in the Australian high country does not reduce the risk of fire’^[6].

Government reports
A number of government inquiries have examined the effect of grazing on fire prevention. Among these, the ‘Esplin Report’ into the 2002-3 fires concluded: “… grazing, associated with firing in forests in the past, appears to have changed the fuel array in forests to one dominated by shrubs rather than grass, a change likely to have increased fire proneness and the chance of intense fires … Recommendation: That, according to available scientific evidence, a decision regarding cattle grazing in the High Country should not be based on the argument that ‘grazing prevents blazing.’ ^[7]

In 2005, the Victorian government’s Alpine Grazing Taskforce stated: ‘Both grazed and ungrazed areas were burnt and unburnt in the 2003 fires, with fire severity predominantly determined by the prevailing weather conditions, topography, fuel loads and fuel flammability types, not whether an area has been grazed’ ^[8].

And a post script
A firefighter helping fight the Mary’s Hill Fire, a few kilometres north of the Blue Waterholes Campground, reported in Jan 2020, ‘One of the more remarkable sights I witnessed was stallion piles of horse dung burning and then creating new fires as it was blown around by the local winds – it’s super dry out there’^[9].

[1] Williams, R.J., Wahren, C.H., Bradstock, R.A. & Müller, W.J. (2006) Does alpine grazing reduce blazing? A landscape test of a widely-held hypothesis. Austral Ecology, 31, 925-936.

[2] For example: Williams, R.J. & Ashton, D.H. (1987) The composition, structure and distribution of healthland and grassland communities in the subalpine tract of the Bogong High Plains, Victoria. Australian Journal of Ecology, 12, 57-71.

[3] Williamson, G.J., Murphy, B.P. & Bowman, D.M.J.S. (2014). Cattle Grazing and Alpine Fire Severity. Austral Ecology, 39, 462-468.

[4] Williams, R.J. & Ashton, D.H. (1988). Cyclical Patterns of Regeneration in Subalpine Heathland Communities on the Bogong High-Plains, Victoria. Australian Journal of Botany, 36, 605-619.

[5] Geoffrey Hope. Peat bog and fen impacts: feral horse damage to soft terrain – bogs and fens in the Snowy Mountains in Graeme L Worboys (ed.) Feral horse impacts: the Kosciuszko Science Conference, conference abstracts. [Canberra}: Australian Academy of Science, Fenner School of Environment and Society, Deakin University, 2018. Pages 54-55. 

[6] Ecological Society of Australia. Alpine grazing: does it reduce blazing? Hot Topics series, 2 Dec 2013. https://www.ecolsoc.org.au/?hottopic-entry=alpine-grazing-does-it-reduce-blazing

[7] Report of the Inquiry into the 2002-2003 Victorian Bushfires. Bruce Esplin, Chairman. Department of Premier and Cabinet (2003)

[8] Report of the Investigation into the future of Cattle Grazing in the Alpine National Park. Alpine Grazing Taskforce, Department of Sustainability and Environment Vic (2005)

[9] Personal communication, 17 Jan 2020, for details contact Reclaim Kosci