Underpinnings of fire management for biodiversity conservation in ...

Underpinnings of fire management for biodiversity conservation in reserves
or more likely parts of their landscapes, fit within the model and to what extent the model (like all
models) meets their needs. For example, in Cooleman Ridge Reserve (part of Canberra Nature Park in
the ACT and an area well-known to the author), there are gradients in grass communities in which the
exotic annual Wild Oats (Avena sp.) is common on some ridges, natives such as Stipa are common mid
slope and the exotic Phalaris aquatica often dominates lower slopes. Would the addition of livestock
decrease the exotics and enhance the natives? A fence-line effect, associated with a farm grazed
mostly by horses, suggests that Phalaris could be greatly diminished by horse grazing, while native Stipa
would be enhanced (on lower slopes). However, a proliferation of exotic Patterson’s Curse (Echium
plantagineum) may accompany the change. At the same time, would adding livestock cause the
diversity to decline on the mid slopes, where the native species are common? If the perennial Phalaris
is to be removed, intervention of some sort seems necessary. If removal was successful, there may not
be a soil-seed pool of native species to replace it and there is the possibility that replacement might be
by annual exotics, such as Echium. The model suggests that the exotic annual grasses may persist with
added grazing, but again the regime is important to what happens.
Grazing regimes based on exotic animals, such as livestock, can affect grassland biodiversity, as
is evident historically. For reserves, removal of livestock can enhance biodiversity outcomes, while
retention also seems to maintain it in some cases. The cautious approach, encouraged here, is to
avoid livestock grazing in reserves where biodiversity is the main aim of management. There seems to
be little known of grazing-regime effects over long periods, so no effect in a short-term experiment
does not necessarily mean no effect in the long-term; recovery processes may take decades and
be hard to discern. Positive effects on particular species or even communities may be achieved by
changing the fire regime, rather than retaining a particular grazing regime (e.g. see Davidson 2005).
The less cautious approach is to introduce livestock. Such a policy implies an obligation to assiduously
measure, record and report the grazing-regime effects on biodiversity of native organisms, because of
the lack of such animals in pre-European settlement of Australia; and that livestock grazing regimes
can replace certain fire regimes. An intermediate position is to allow the grazing of livestock in assetprotection
zones to reduce grassy fuels where biodiversity conservation may be subsumed as an aim
below that of fire protection.
Influences on today’s ecosystems are either quantitatively or qualitatively different from those in the
past. New influences include fertiliser or herbicide drift and the effects of feral animals, domestic
stock and exotic plants. Old influences that have been eliminated are those of native predators and
other vertebrates and changed fire regimes (see Gill 2003). Many reserves have a problem with too
much grazing by exotic, feral animals. Continual research and monitoring is necessary for further
understanding of the effects of past and present livestock grazing in various regimes. The effects on
plant species in reserves will depend on regimes, which indigenous or exotic plant and animal species
are present and their dominance relationships. Effects of grazing or browsing regimes can affect many
components of the ecosystem, not just the plants. Perhaps some of the complexity that may arise is
evident in the case study of Burrows and Friend (1998), in which trees regenerating after fire were
browsed by locusts to the point where the trees died (a burning–browsing effect) – ‘permanently
changing this site from a rock she-oak thicket capable of supporting [native] red-tailed Phascogales to
a grassland affording little habitat for the species’.
Sophisticated computer simulations that allow the manager to explore the many possibilities of fuel
management, at least, are being developed. Such simulations can be seen as decision-support tools
that may allow the best choices to be based on available information; assessment of such choices
through monitoring would remain important. Effects of fuel-management practices on biodiversity of
any local area are much more difficult to model, and empirical methods are to be recommended.
Finally, livestock grazing is not just herbivory. For management it involves infrastructure, such as
fencing, watering points, tracks and even yards, which all have their effects. Grazing, in itself, involves
seed carriage, camping and nutrient concentration, baring of soil in heavily used areas, defecation,
urination, breakage of woody plants and trampling, amongst other things. There is a plethora of
possible grazing regimes, even if herbivory is considered as the only influence, but the effects multiply
when these other aspects of grazing are taken into account.
Fire and adaptive management 69