Literature review: Impact of Chilean needle grass ... - Weeds Australia

But little is known anywhere in the world about the motives, scale and ecological significance of aboriginal fire management
(Murphy and Bowman 2007). The palynological records of grasses in lake and swamp cores indicate that south-eastern
Australian grasslands existed long before aboriginal occupation and are not of anthopogenic origin (Jones 1999b, Kershaw
2000); rather, aboriginal activities modified existing grassy ecosystems and shifted their boundaries (Jones 1999b).
The European explorer Thomas Mitchell thought that burning was critical to aboriginal management of country: “fire, grass,
kangaroos, and human inhabitants seem all dependent upon each other for existence” (Mitchell 1848, cited by Murphy and
Bowman 2007). Fire use in hunting had two aspects: as a direct tool to flush the animals or drive them towards waiting hunters,
and habitat manipulation, in which the young green growth attracted the animals, increased the carrying capacity and made the
prey easier to locate and kill (Murphy and Bowman 2007). Numerous ecological studies show that kangaroos are attracted to
burnt areas but there has been little investigation of the mechanisms that cause this response. In studies in northern Australian
savannah and seasonal wetland Murphy and Bowman (2007) found that the abundance of Macropus spp. scats was much greater
in burnt than unburnt moist areas, and in unburnt than burnt dry rocky areas, from 4 weeks to 1 year post-fire. Kangaroos moved
into the burnt moist areas away from burnt, dry rocky habitats. The resprouting grass foliage contained higher N concentrations
than senescent foliage and may have provided macropods with better quality nutrition. Aboriginal burning may indeed have
created a self-reinforcing cycle by creating a mosaic of habitat patches, very different to that subsequently developed by
Europeans.
Pastoral development had an immediate and devastating effect on the aboriginal population. Introduced livestock destroyed their
prime feeding grounds and muddied and destroyed the waterholes and soaks (Zola and Gott 1992). Considerable numbers of
aborigines were shot by European occupiers. Smallpox had already decimated the Victorian aboriginal population by 1835 and
populations collapsed to an estimated 1,700 in 1871 and 850 in 1901 (Coutts 1982). The cessation of aboriginal fire regimes
resulted in well-documented substantial change in vegetational structure, particularly involving increases in tree cover (Hope
1994).
European Management
European occupation of Australia brought a novel range of exogenous disturbances that resulted in rapid, abrupt changes to
Australian grasslands (McIntyre and Lavorel 1994). Aside from the changes in land use that must have occurred as imported
diseases decimated aboriginal populations, sheep and cattle grazing was the first major European impact and the shift to frequent
livestock grazing is generally recognised as the major cause of vegetation change (Dorrough et al. 2004). Grasslands were
preferentially occupied by squatters and their livestock very early in the colonial period. Pastoral settlement commenced in the
1820s in the Southern Tablelands of NSW and the ACT (Sharp 1997) and in the early 1830s on the Northern Tablelands
(Johnson and Jarman 1975). In Victoria occupation commenced in the mid 1830s and there were 25,000 sheep in the colony
before legal settlement commenced in 1836 (Mansergh et al. 2006a), over 41, 000 by May of the following year, along with 155
cattle and 75 horses (Jones 1999b). Sheep numbers reached 700,000 by 1841 and doubled by 1843 (Gott 1983), by which time
most of the grasslands in Victoria outside of Gippsland had been occupied (Jones 1999b). There were over 6 million sheep in the
1850s, along with about 1 million cattle (Mansergh et al. 2006a). On the New England tablelands of NSW 66 stations occupied
all of the best grazing land by 1840 and only a few more were added in rougher country by 1848 (Johnson and Jarman 1975).
Thirty million sheep had been introduced to the grassy plains of Victoria and NSW by 1851 along with 1.7 million cattle and
32,000 horses (Lunt et al. 1998). European occupation, at least in Victoria, probably coincided with a major climate shift to drier
and hotter conditions (Jones 1999b) which probably exacerbated the impact of livestock. However the impact on native
grasslands up until the 1860s were relatively mild compared with what followed (Scarlett and Parsons 1993).
In Victoria the Selection Acts of the 1860s led to the alienation of large areas of Crown land and the advent of major cultivation,
particularly cereal growing (Scarlett and Parsons 1993). In NSW the Land Act of 1861 allowed occupation of areas up to 259 ha
before government surveys, and fencing began to be used instead of shepherding (Johnson and Jarman 1975). Land grazing
under licence became legitimate in Victoria in the period to 1900. By 1891 livestock farming on large freehold properties was
well established, particularly in the Western District (Powell and Duncan 1982). Landscape change was intensified by the
extension and intensification of more efficient types of fencing (Powell and Duncan 1982). By 1910 pasture occupied c. 12
million ha in Victoria, of which