Some Problems Associated with Land Management

3.1.2.1 Introduced Species

Monitoring and assessing the impacts of land-use forms a major theme for the CSIRO Centre for Arid Zone Research (CAZR) (Bastin, 2002, CSIRO Centre for Arid Zone Research, 2005b). There are numerous reports of how the introduction of exotic foraging species and grazing by domestic stock have degraded the floral communities of the Australian arid zone (for example (Rechner et al., 1992), (Wopfner and Twidale, 2001) and (Mackay and Eastburn, 1990)). The effects of the introduction of exotic foraging species, for example rabbits or stock, are illustrated by studies in the T.G.B. Osborne Vegetation Reserve at Koonamore in South Australia. These studies show a steady decline in the surviving number of mulga (Acacia aneura) trees (Morton, 1992) coinciding with the introduction of the exotic faunal species. Increases in land degradation and surface erosion have been noted where overstocking or deliberate land clearing have resulted in the denudation of the landscape (Wopfner and Twidale, 2001).

The introduction of weed species in the finely balanced and sensitive arid environments also has taken a toll, for example “Salvation Jane” also known as “Paterson’s Curse” (Echium plantagineum) (Carnahan and Deveson, 1990).

3.1.2.2 Regeneration

The Grazing Gradient (Brook et al., 2001, Bastin, 2002) shows how remote sensing techniques can be used to determine overgrazing in a given paddock; however, the method detects vegetation growth only, not which species are present. In the arid zones it is usually native grasses and shrubs that are grown as unimproved pasture (Bastin, 2005). Many of the native forage species, whether they be grasses or shrubs, are not regenerating (eg mulga (Acacia aneura) (Wopfner and Twidale, 2001) or kangaroo grass (Themeda triandra) (Lunt, 2003)), sometimes due to overgrazing by domestic stock; sometimes by feral exotic species including rabbits, goats, donkeys, camels, horses etc (Bastin, 2005).

Table 3 Summary of Arid and Semi-arid land vegetation associations (after (Morton, 1992)). Association Percentage of Australian arid zone Dominant vegetation species

Comments Example in the Woomera area

Acacia Shrubland 33 Acacia aneura,

(mulga)

A dull grey shrub growing to a height of around 10 metres. Its tolerance of a wide variety of conditions means that it is found throughout the arid zones except on sandy or saline areas

Hummock Grassland

31 Grasses from the genera Triodia and Plectrachne

Unique to Australia, it is dominated by low spiky vegetation growing as metre high, three-metre diameter clumps in red sands. The grasses within these clumps are commonly called “porcupine grass.”

Tussock Grassland

9 Grasses from the genus Astrebla

The tussock grassland is heavily grazed. These grasslands grow on the black-soil plains, on clay soils and Sturt’s Stony Desert

Association Percentage of Australian arid zone Dominant vegetation species

Comments Example in the Woomera area

Chenopod Shrubland

8 Herbs, and shrubs from the family

Chenopodiaceae

The flora of chenopod shrubland is generally low growing (to about 1 m) and sparsely distributed. It comprises both perennial and ephemeral species and often has a distinctive silvery grey appearance, which may be due to the pubescent nature of the foliage, or to the presence of small salt crystals on the surfaces of the leaves. Some genera have high intra-species variability, for example

Atriplex, commonly known as saltbush. The variability of

normally distinctive features such as leaf shape and flower morphology makes field identification of the species of this genus, difficult (George, 1984). The fruiting body form is usually the diagnostic feature that defines the species. Around the inland drainage basins, salt tolerant species and species strains establish and grow where they can, generally on the less saline areas and dunes. Halophytes are the dominant species in the saline areas, and comprise much of the low growing chenopod shrubland. Chenopods also occur as understorey species in Acacia and Eucalyptus shrublands.

Association Percentage of Australian arid zone Dominant vegetation species

Comments Example in the Woomera area

Eucalyptus

Shrubland

8 Multi-stemmed trees, also known as mallee, from the genus

Eucalyptus

The Eucalyptus shrubland contains a variety of low- growing trees known as mallee. The mallee occurs on the margins of the eastern and southern fringes of the other shrublands

3.1.2.3 Land Management Practices

Flannery, (1994) in his book “The Future Eaters”, explains how the style of life believed to have been followed by the Aborigines was notable in its lack of archaeological evidence; however, indigenous people are believed to have followed a nomadic lifestyle, in balance with the land systems. They farmed the land using fire (Langton, 1998). This is believed to have selectively encouraged certain flora and fauna species so that their survival was interdependent (Morton, 1992, Langton, 1998). With the alteration of land management to a pastoral regime, the flora have suffered (Carnahan and Deveson, 1990, Bastin, 2005, CSIRO Centre for Arid Zone Research, 2005b, CSIRO Sustainable Ecosystems, 2005). Animals dependent on specific habitats are also under threat. Morton (1992) describes how the overgrazing by domestic stock is believed to have altered the vegetation that sheltered the rat-kangaroos, Bettongia and Caloprymnus; hare wallabies Lagorchestes and Lagostrophus; nail-tailed wallabies Onychogalea; and bandicoots Chaeropus, Perameles and Macrotis; causing a dramatic decrease in their populations and extinction of other species. He also explains that the change in the fire regime is believed to be responsible for the collapse of the range of the rufous hare-wallaby, Lagorchestes hirsutus, which is believed to be dependent upon the new growth encouraged by the selective burning of the grasslands by the original inhabitants (Langton, 1998).