The conservation status of the commercially harvested kangaroo species in NSW reflects their abundance and thus their utilisation. No commercially harvested kangaroo species in NSW is listed as a threatened or endangered species under either State or Commonwealth legislation (Table 1). In addition, the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species identifies all of the kangaroo species subject to commercial harvesting in NSW as lower risk, in the sub-category of least concern, which encompasses species that do not qualify for the conservation dependent and near threatened sub-categories (Table 1).
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is an international agreement between governments – including the Government of Australia – that aims to ensure international trade in wild animals and plants does not threaten their survival. CITES accords varying degrees of protection to more than 30,000 species of animals and plants, which are listed in the three CITES Appendixes. None of the kangaroo species commercially harvested in NSW is listed in the CITES Appendices (Table 1).
Table 1: The New South Wales, Commonwealth, IUCN and CITES conservation status of the kangaroo species to which this plan relates
Species
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NSW
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Commonwealth
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IUCN
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CITES
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Red kangaroo
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Common
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Not listed
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Lower Risk
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Not listed
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Eastern grey kangaroo
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Common
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Not listed
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Lower Risk
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Not listed
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Western grey kangaroo
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Common
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Not listed
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Lower Risk
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Not listed
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Wallaroo
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Common
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Not listed
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Lower Risk
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Not listed
| 3.4. Threats, issues and assessment of impacts
In the context of commercial kangaroo harvesting in NSW: threats to the conservation status of harvested kangaroo species are limited; issues relating to the conservation and harvesting of kangaroos are well understood; and assessments of the impacts of harvesting on kangaroos, as well as other species, habitats and ecosystems, are comprehensive.
3.4.1. Threats and issues pertinent to the conservation status of kangaroos
The conservation status of kangaroos in NSW has the potential to be threatened by a range of environmental and anthropogenic factors. Many of these potential threats – from climate change, drought and flood to disease and predation – are ecosystem and environmental processes beyond the control of OEH. Nevertheless, as evidenced by the scientific literature, these processes are not considered a threat to the conservation status of kangaroos (Table 2).
Potential anthropogenic threats to the conservation status of kangaroos principally arise from the commercial harvest. However, in 30 years of commercial harvesting, viable populations of the harvested kangaroo species have been maintained across their natural range and, moreover, the distributional ranges of eastern and western grey kangaroos have expanded. Accordingly, commercial harvesting is not considered a threat to the genetic integrity or conservation status of kangaroos in NSW (Table 2). However, to ensure the commercial kangaroo harvest in NSW remains sustainable and does not in the future jeopardise the viability of kangaroo populations across their range, OEH enacts a range of management controls, including:
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Undertaking regular and ongoing monitoring of kangaroo populations. The strictly standardised survey techniques employed in NSW for the broad-scale monitoring and estimating of kangaroo populations are widely regarded as best practice, both in Australia and overseas (Caughley et al. 1976; Caughley & Grigg 1981; Anderson & Southwell 1995; Southwell et al. 1995; Pople 2004; Pople et al. 2006; Pople 2008). Indirect monitoring is also undertaken via harvest statistics, but is currently used only to supplement direct monitoring from aerial surveys. Predictive models using harvest statistics, rainfall and other data are not yet sufficiently advanced to replace direct monitoring of populations (Pople et al. 2010)
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Managing the commercial harvest using a proportional harvesting strategy based on regular estimates of abundance. Proportional harvesting strategies have been well studied and are considered safe and efficient for fluctuating populations (Caughley 1987a; Engen et al. 1997). Moreover, the NSW program of regularly monitoring and estimating abundance allows for any other mortality agents acting on kangaroo populations to be accounted for in the setting of annual commercial harvest quotas (e.g. animals lost through drought, disease, or road kill).
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Using conservative and up to date species correction factors. OEH employs correction factors in estimating kangaroo abundance from aerial survey data that are generally regarded as cautious. In addition, OEH works collaboratively with universities to ensure correction factors applied remain appropriate. For example, OEH and the University of New England conducted a three-year research project (1998-2000) examining fixed-wing aerial surveys. As a result of this research, OEH has since 2001 implemented new bio-regional correction factors for grey and red kangaroos, implemented revised proportions of eastern grey and western grey kangaroos and implemented a new data analysis protocol.
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Setting commercial harvest quotas at levels that are considered ecologically sustainable for kangaroo populations. Commercial harvest quotas set at 15% of the population estimate for eastern grey kangaroos, western grey kangaroos, wallaroos and 17% of the population estimate for red kangaroos are not only regarded as ecologically sustainable in the scientific literature (e.g. Caughley 1987a; Hacker et al. 2003, 2004), but are demonstrably sustainable. Additional protection for low populations is achieved by reducing or suspending the harvest if populations fall below thresholds based on historical fluctuations (Pople 2008).
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Providing refuge habitat. In NSW kangaroos cannot be commercially harvested in conservation reserves, a total area in excess of four million hectares or approximately 6.3 percent of the commercial harvest zones. In addition, the commercial kangaroo harvest is patchy within Kangaroo Management Zones and individual properties, leaving many other areas of unharvested or refuge habitat (Tenhumberg et al. 2004).
3.4.2. Assessment of the impacts of commercial kangaroo harvest on other species, habitats and ecosystems
Impacts on species, habitats and ecosystems resulting from actions detailed within this management plan are unlikely to be significant, and in many instances are expected to be positive (Table 3).
Table 2: Threats and issues pertinent to the conservation status of kangaroos
Threats
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Comments
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Selected References*
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Drought
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Rainfall via its impact on plant productivity is the single most important factor impacting on kangaroo populations and droughts can greatly reduce kangaroo numbers. However, kangaroos are well adapted to a dynamic environment and populations recover quickly after drought-driven population crashes, even with continued harvesting. Therefore drought is not considered a threat to the conservation status of kangaroos.
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Bayliss 1987; Cairns & Grigg 1993; Cairns et al. 2000; Caughley et al. 1985; McCarthy 1996; Pople 2003; Pople et al. 2010; Robertson 1986; Dawson et al. 2007; Underhill et al. 2007; Fensham & Fairfax 2008
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Disease
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A range of parasites and pathogens affect kangaroo populations, including cystic hydatid disease, Cryptospiridium, Ovine Johnes Disease, Toxoplasmosis and Herpes. Effects on individual kangaroos range from little impact to severe clinical disease and mortality. Epidemics have caused significant short-term reductions in kangaroo numbers in particular areas; however, these populations have recovered rapidly. Diseases are not considered important agents of mortality in kangaroos at the population level in the long-term and therefore do not pose a threat to the conservation status of kangaroos.
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Caughley 1987a; Gilroy et al. 1999; Kirkpatrick 1985; Pople & Grigg 1999; Speare et al. 1989; Banks et al. 2006; Barnes et al. 2007; Power et al. 2005; Ryan et al. 2008; Power et al. 2009; Cleland et al. 2010; Banazis et al. 2010; Parameswaran et al. 2009; Smith et al. 2008; Garnick et al. 2009
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Flood
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Flooding has been found to affect the short-term distribution and abundance of kangaroos and has been associated with occasional localised epizootics. Flooding is not considered a threat to the conservation status of kangaroos.
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Choquenot 1991; Clancy et al. 1990
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Habitat loss and modification
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The three largest species of kangaroos have benefited significantly from habitat modification, with numbers increasing and ranges extending due principally to the expansion of grasslands. Conversely, kangaroo numbers have generally declined where there is intensive agriculture, urbanisation or extensive clearing. However, despite more than 200 years of heavy exploitation and clearing of the land the larger kangaroos have maintained their populations or increased in abundance and range; accordingly, habitat loss and modification is not considered a threat to the conservation status of kangaroos.
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Calaby & Grigg 1989; Dawson et al. 2004; Pople et al. 2010; Short & Grigg 1982
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Climate change
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Impacts on kangaroos from climate change are difficult to predict but are likely to be negative. Effects on individuals include changes to forage composition, seasonal events, fecundity, survival and behaviour, while effects on populations include changing species abundance, distribution, and genetics.
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Ritchie & Bolitho 2008; Dunlop & Brown 2008; Jonzen et al. 2010
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Harvesting – general
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In 30 years of managed harvest viable populations of the harvested kangaroo species have been maintained across their natural range. Furthermore, the distributional ranges of eastern and western grey kangaroos have expanded. Harvesting is not considered a threat to the conservation status of kangaroos.
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Cairns & Coombs 1992; Calaby & Grigg 1989; Dawson et al. 2004; Grigg & Pople 2001; Pople et al. 2007; Viggers & Hearn 2005
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Harvesting – genetic impacts
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Harvesting, especially non-random or selective harvesting, has the potential to alter the genetic structure and genetic diversity of a population. However, there is no theoretical, empirical or modelled evidence of genetic impacts at current levels of kangaroo harvesting. Therefore harvesting is not considered a threat to the genetic integrity or conservation status of kangaroos.
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Clegg et al. 1998; Hacker et al. 2003, 2004; Hacker & McLeod 2003; Hale 2001, 2004; Tenhumberg et al. 2002, 2004; Zenger et al. 2003; Neaves et al. 2009, 2010; Allendorf et al. 2008; Mysterud 2011
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Predation
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In some circumstances dingoes (Canis lupus dingo) have been shown to limit kangaroo populations, and there is increasing evidence for this species having a regulatory effect. Other predators such as foxes (Vulpes vulpes) and wedge-tailed eagle (Aquila audax) do not appear to exert much influence on the harvested species of kangaroo. Predation is not considered a threat to the conservation status of kangaroos.
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Banks et al. 2000; Caughley et al. 1980; Corbert & Newsome 1987; Jarman & Denny 1976; Pople & Page 2001; Thompson 1992; Letnic & Koch 2010; Fillios et al. 2010
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Table 3: Impacts of the commercial kangaroo harvest on other species, habitat and ecosystems
Potential Impacts
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Comments
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Selected References*
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Reduction in soil quality and land stability
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There is unlikely to be a reduction in soil quality or land stability as a consequence of the commercial kangaroo harvest as harvesters generally operate on already-formed tracks. Moreover, kangaroo harvest off cuts have been shown to contribute to soil nutrient retention and cycling, thereby improving soil quality.
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Wilson & Read 2003
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Detrimental effects on water bodies, watercourses, wetlands and natural drainage systems
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There is no evidence that suggests the commercial kangaroo harvest will have detrimental effects on water bodies, watercourses, wetlands and natural drainage systems.
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Vegetation clearing or modification
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No vegetation is likely to be cleared or modified as a consequence of the commercial harvest. The commercial harvest may however provide indirect benefits to vegetation by potentially contributing to an integrated approach to reducing total grazing pressure or facilitating the retention of vegetation that provides habitat for kangaroos by private landholders.
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Fisher et al. 2004; Grigg 1988, 1995
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Detrimental effects on threatened flora species, populations, or their habitats
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There is no evidence that the commercial kangaroo harvest has a detrimental effect on threatened flora species, populations, or their habitats.
|
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Endangering, displacing or disturbing native fauna, or creating a barrier to their movement
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Native fauna is unlikely to be endangered, displaced or disturbed as a consequence of the commercial kangaroo harvest. The commercial harvest is, moreover, unlikely to create a barrier to the movement of native fauna. Kangaroo harvest off cuts are however utilised by birds of prey thereby benefiting these species.
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Read & Wilson 2004
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Detrimental effects on threatened fauna species, populations, or their habitats
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There is no evidence that the commercial kangaroo harvest has a detrimental effect on threatened fauna species, populations, or their habitats. There may be indirect effects on threatened fauna species and/or populations as a consequence of the commercial kangaroo harvest, however such effects are not likely to be significant (see section on introduced predators below).
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Detrimental impacts on ecological communities of conservation significance
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Ecological communities of conservation significance are unlikely to be impacted by the commercial kangaroo harvest.
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Positive effects on introduced predators
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Kangaroo harvest off cuts are utilised by introduced predators, particularly foxes (Vulpes vulpes) and may sustain populations of these predators during periods of low prey availability. Maintenance of artificially high predator populations may in turn threaten prey populations, including endangered taxa. However, given that many harvesters presently bury harvest off cuts and that harvest off cuts are widely and randomly dispersed across the landscape, it is unlikely that the commercial kangaroo harvest will have a significant positive effect on populations of introduced predators.
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Kay et al. 2000; Read & Wilson 2004; Saunders et al. 1995
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Positive effects on introduced herbivores
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The commercial kangaroo harvest, by reducing kangaroo populations and thus competition, may allow populations of introduced herbivores such as goat (Capra hircus) and rabbit (Oryctolagus cuniculus) to increase. However, the limited magnitude of the reduction in kangaroo numbers coupled with the ongoing and extensive pest animal control programs undertaken in NSW ensure that the commercial kangaroo harvest is unlikely to have a significant positive effect on populations of introduced herbivores.
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* Where applicable and/or available
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