Underpinnings of fire management for biodiversity conservation in ...

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Fire and adaptive management 58 Chapter 4 Fuel modification by grazing or browsing Introduction Whether or not grazing by domestic stock has a role in conservation reserves is a longstanding issue in Australia, particularly in the southeast where grazing by sheep and cattle in the mountains has been controversial for at least 60 years. In 1943, domestic animal grazing was banned in what was soon to become Kosciuszko National Park (Clark 1992). Observation of detrimental effects of grazing (often accompanied by burning) in mountain environments go back to at least 1893 (Helms 1893), and elsewhere even before that, ‘Since the country was stocked with sheep & cattle several native grasses have disappeared …’ (1853 letter reproduced in Brown 1963). Domestic stock grazing in Victorian high-country national parks continued until recently (2005), amid considerable controversy. Grazing by domestic animals controversially continues in some conservation reserves outside the high country in the ACT (Canberra Nature Park; Plate 4.1; Lunt et al. 2007), Victoria (Wong et al. 2006) and undoubtedly elsewhere. In the forested escarpment country of north-eastern NSW, grazing by domestic animals was phased out as lands came under national park jurisdiction (Henderson and Keith 2002). Feral animals, such as goats, pigs, deer, rabbits, hares and horses, graze national parks and other reserves, along with native herbivores, such as kangaroos, wallabies, possums and potoroos. The grazing issue is relevant to conservation on farms, forests and pastoral properties. Plate 4.1 Young exotic cattle grazing a conservation reserve in Canberra, ACT (Gill 2006). The subshrub in the foreground is the native Hardenbergia violoacea. The green graminoid in the foreground is the native Lomandra sp. The green grass at the base of the hill is the exotic Phalaris aquatica. Some reserve managers may be tempted to use domestic stock as a means of fuel modification in reserves for biodiversity conservation. There are various reasons why this might be so, including: • Reduction in grassy fuels and its perceived benefit to fire suppression and control without ‘risky’ prescribed burning operations • Assisting drought-stricken, or other, local pastoralists (‘good neighbour policy’) • A cultural legacy (‘it’s traditional’) • A way to reduce cover to allow indigenous species of plants to persist (‘it works’) (Kirkpatrick et al. 2005). It may seem obvious that grazing would significantly reduce the fire proneness of vegetation, but this is not necessarily so if the dominant fuel element – as opposed to the grazing element – is not selected by the animals, even if it is grass: ‘The most abundant and dominant herb is the snow grass … and as this is so obvious it is generally assumed that the sheep and cattle are grazing upon it. Close observation, however, shows that … the greater part of the rather wiry, tough, grassy tussock is not favoured by the animals except in years of intense drought. It is for this reason that most graziers, especially of sheep, have adopted a policy of regularly burning the snowgrass in the high country (Turner 1962).
Underpinnings of fire management for biodiversity conservation in reserves Grazing for fuel reduction needs to be extensive and complete enough to have a significant effect on fire occurrence, intensity or rate of spread; recognising that fire can still spread across eaten out paddocks in high wind conditions (Cheney et al. 1998). In short, grazing that removes fuel biomass will reduce potential fire intensity (by definition). If it reduces grass height, it will reduce flame height (Cheney and Sullivan 1997, p. 24). Light grazing may have a relatively small effect on rate of spread, and even when eaten out, the rate of spread in grassland may be approximately 50% of that when there was no grazing (Cheney and Sullivan 1997, p. 39; Cheney et al. 1998). A useful effect of grazing for the fire manager would be to reduce the proportion of dead matter (curing) in a pasture, which can assist in fire control. If the pasture can be kept green, and therefore moist, for longer periods than otherwise, then the chances of fire spread are reduced. This may depend on keeping pastures heavily grazed. Grazing will have most influence on potential fuels where dominant species are highly palatable and accessible. In western New South Wales, grazing pressure has lead to the death of grasses and their replacement by woody plants formerly kept in check by repeated fires (Daly and Hodgkinson 1996). This agro-ecosystem seems to have changed from a largely fire–grass–shrub system to a sheep–grass– shrub system to a shrub system (see also Janssen et al. 2004). In the review of Lunt et al. (2007), the demise of dominant palatable chenopods in Riverina shrublands, and their replacement by grasslands, is described – the reverse of the previous example, as far as the sequence of life forms is concerned. The presence of exotic grazing animals in a conservation reserve is usually seen to be contrary to the aim of biodiversity conservation. Removing exotic animals, domestic or feral, is usual when a reserve is declared. Thus there are programs to control the European Rabbit (Oryctolagus cuniculus) in conservation areas, presumably because it is exotic as well as a species causing damage to the assets of the area. Other feral animals are usually controlled as well. Furthermore, grazing has been identified as a threatening process (potentially causing extinction). Garnett and Crowley (2000) noted that grazing by sheep and cattle is a threat to 53% of mainland birds. Leigh et al. (1984) stated that ‘Grazing by domestic, feral and native animals is believed to have been responsible for the presumed extinction of 31 species’ (p. 35) of plants; 55 extant species were considered endangered by grazing in 1984. Eleven species of fauna were threatened by grazing in the Australian Alps according to Coyne (2001). In its simplest form, opposition to grazing by domestic animals in conservation areas is a philosophical one. The presence of an exotic herbivore, especially if it is in large numbers, is the antithesis of the aim of conserving the indigenous biota. In its more complicated form, the issues centre on the: • Environmental effects of grazing regimes in general (with potentially positive and/or negative effects) • Possible extent of improvement of fire suppression due to the effects (including no significant effect) of grazing regimes on fuels • Extent to which longer-term changes to vegetation type, animal habitat or landscape processes affect conservation quality or fuel type due to grazing regimes. What is seen as the important environmental effects of grazing regimes varies widely according to the criteria applied. Pastoralists may primarily be interested in economic returns from livestock, but secondarily wish to maintain as many indigenous plant species as possible. Conservation managers may primarily be interested in conserving indigenous plants and animals, but see livestock as a way to reduce fuel loads. The primary concern here is with conservation of indigenous biodiversity in reserves, but the practice of grazing livestock in reserves draws attention to grazing effects, both positive and negative, in relation to fire-and-fuel management and biodiversity conservation. The environmental effects of grazing are examined, as much of the literature is concerned with grazing versus no grazing rather than with the effects of grazing regimes. Grazing regimes are then defined in parallel with fire regimes – type of animal, intensity of grazing, intervals between grazing and seasonality of grazing, and their effects discussed. Fire and adaptive management 59
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