Underpinnings of fire management for biodiversity conservation in ...

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