Land management for agricultural production is reviewed in Chapter 5: Land. Each land-use system entails some degree of clearing and fragmenting of native ecosystems, and grazing systems have the added impact of large introduced animals on landscapes and species. Research reported in previous national SoE reports has found that artificial watering points allow domestic stock to forage in areas that would otherwise be too dry for them and this has spread the impacts of grazing widely across arid Australia.15,112
Williams and Price113 recently reviewed the literature on impacts of livestock and other industries that produce protein from domestic animals, or from wild animals (e.g.kangaroos or wild-caught fish). Their conclusions (Table 8.21) illustrate the wide range of direct and indirect impacts of these industries and particularly the high relative impacts of beef production. The authors point out, however, that management in the red meat industries, which once had very high impacts on biodiversity, has improved greatly.
Around 60% of Australia’s area is used for producing livestock.15 Pastures are still dominated by native plant species in around 95% of this area (i.e. the rangelands of central and northern Australia), although invasion of northern Australia by introduced grasses is of increasing concern114-115 and has been listed as a key threatening process under the EPBC Act since 2009. The general environmental impacts of extensive grazing are discussed in Chapter 5: Land.
|Note that the pressures exerted by any individual industry are relative to other industries, and that high relative pressures do not necessarily imply high absolute pressures on biodiversity.|
|Protein source||Potential relative contribution to pressure on biodiversity|
|Vegetation clearance||Altered fire regime||Altered grazing regime||Altered hydrology||Trampling and compaction||Invasive species||Pollution (air, water, land)||Disease and pathogens||Climate changes||Direct loss of biota|
|Fish (wild catch)||L||L||L||L||Ho||L||L||L||L||Hw|
H = high; L = low; M = medium; O = ocean floor dragging; w = wild catch or harvest
Source: Williams & Price113
Impacts of grazing on biodiversity include changes in the proportions of different plant species due to selective removal by the grazers—including total removal of some species—and consequent or associated promotion of invasion by weeds. Grazing also changes soil characteristics affecting water infiltration and erosion, and can lead to altered fire regimes when the balance of species types and the structure of landscapes are changed, or when land is managed for pasture production. In the past, exotic plant species were introduced to pastures in the mixed farming areas (the so-called ‘wheat–sheep’ belt) of southern Australia to increase their nutritional value for grazing domestic animals (sheep and cattle). All these effects on native plants also affect the native animals that rely on them for food and habitat.
The control of dingoes is one of the activities of livestock production that has an increasing impact on biodiversity. Recent research has suggested that when dingo numbers are kept in check, other biodiversity suffers because the impacts of introduced cats and foxes increases, and the impacts of these predators is far greater than that of dingoes.116 Dingoes also appear to keep numbers of cats and foxes in check. Grazing pressure, together with the effects of invasive species like cats and foxes, and changed fire regimes, have been implicated in the major recent declines in mammals and birds in central and northern Australia (Box 8.3).15,117-118
Grazing is one example of a pressure that interacts strongly with a range of others. For example, most land clearing is to produce pasture for stock; livestock are a major reason for the introduction of invasive plants like gamba grass and buffel grass; suppression of top predators (e.g. dingoes—see above) is primarily to protect stock; watering points for stock in arid areas also encourage feral pest populations; stock remove the fuel that cool fires need, and encourage woody thickening which can result in stand-replacing fires; catchment-scale soil compaction changes catchment hydrology; and selective grazing removes protective cover, changes the composition of vegetation communities and exposes soils to erosion. These types of interactions apply for most pressures on biodiversity (see Section 3.13).
The recent assessment of Australia’s rangelands (Bastin et al.;119 see Chapter 5: Land) reported mixed impacts of grazing on environmental values, including biodiversity. Similar to other pressures on biodiversity, information on which to base assessments is limited across most of Australia, but several conclusions seem defensible:15
- Grazing pressure is a long-standing and complex threat to biodiversity over much of Australia, with significant impacts related to the extent, duration and management of grazing.
- The greatest effects of grazing occurred rapidly after initial pastoral settlement, but its effects are still evident except where the most biodiversity-sensitive practices are used.
- There is no reason to believe that the history of biodiversity decline in the rangelands has been arrested, and there is evidence that it is accelerating in some areas.
- In the intensive agriculture zones throughout much of southern Australia, native biodiversity has been severely reduced and isolated in mostly small remnant populations that struggle to compete with introduced species under existing land-management regimes and are therefore highly vulnerable to other threats, including invasive species, pathogens, fire and climate change.