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Kangaroos and Land management
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To identify policy settings and industry initiatives that could improve land management in relation to the harvest of kangaroos in rangeland areas. Kangaroos in the context of agricultural production systems The Rangelands encompass 81% of Australia. These are areas where rainfall is too low or unreliable and the soils too poor to support cropping and the native pastures of the rangelands are mostly used for extensive grazing. There is an increasing awareness of the need to match production systems in the rangelands to their environments and recognition in the case of the kangaroo that this animal is well adapted to the rangeland ecosystems. That greater adaptation is because kangaroos are native animals that have co-evolved with the native vegetation. The kangaroo is much more efficient at converting vegetation into protein. As a consequence the kangaroo places less pressure on pasture and water supplies compared with sheep and particularly cattle. This has been established in assessments of total grazing pressure relative to net primary production that use Dry (non-lactating), Sheep Equivalents (DSE) to measure the grazing pressure exerted by domestic sheep and cattle as well as native and naturalised grazers (such as the kangaroo) (Bureau of Rural Sciences 2005; Beeton, Buckley et al. 2006). The DSE of a kangaroo is estimated to be somewhere between 0.2 and 0.7 of a non-lactating sheep (Grigg 2002), while beef cattle have a DSE of about 8 (see Table 1. below.). Using kangaroo population estimates (Caughly, Grigg et al. 1983; Pople and Grigg 1999) and relative DSE's (Beeton, Buckley et al. 2006) show that between 1% and 8% of grazing pressure in Australia is due to kangaroos. For the last two decades environmental scientists have been exploring the sustainable use of native species to generate conservation benefits and there is now a substantial amount of data supporting arguments for greater use of kangaroos as production animals (Wilson 1974; Archer 2002). Both as a way of reducing the total grazing pressure in the rangelands – because the use of kangaroo is a better land management strategy in terms of reducing land
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A publication from the Think Tank for Kangaroos (THINKK) in the Institute of Sustainable Futures at the University of Technology Sydney evaluates the idea that eating wild harvested kangaroo meat is environmentally beneficial, compared to other meats produced on rangelands (Ben-Ami et al. 2010). It finds in the negative. The report purports to be a reasoned and objective analysis based on the science surrounding kangaroo harvesting. Here we examine this document with reference to available literature, and demonstrate that it is neither well-‐reasoned nor accurate. It contains multiple errors of fact, inaccurately represents published research, and makes several invalid and seriously misleading comparisons. In our view, this report makes an inaccurate and potentially misleading contribution to the scientific, legal and social debate on kangaroo management. In the light of these findings we discuss the challenges to academic objectivity and rigour posed by funding of university research by interest groups
Sustainable management of pastures requires detailed knowledge of total grazing pressure, but this information is critically lacking in Australia’s rangelands where livestock co-occur with large herbivorous marsupials. We present the first comparative measure of the field metabolic rate (an index of food requirement) of Australia’s largest marsupial, the red kangaroo (Macropus rufus), with that of domestic sheep (Ovis aries; merino breed). We tested the assumption that the grazing pressure of red kangaroos is equivalent to 0.7 sheep, and show this to be a two-fold overestimation of their contribution to total grazing. Moreover, kangaroos had extraordinarily lower rates of water turnover, being only 13% that of sheep. Consequently, our data support arguments that the removal of kangaroos may not markedly improve rangeland capacity for domestic stock. Furthermore, given the low resource requirements of kangaroos, their use in consumptive and non-consumptive enterprises can provide additional benefits for Australia’s rangelands than may occur under traditional rangeland practices.
Ruminant livestock produce the greenhouse gas methane and so contribute to global warming and biodiversity reduction. Methane from the foregut of cattle and sheep constitutes 11% of Australia's total greenhouse gas emis-sions (GHG). Kangaroos, on the other hand, are nonruminant forestomach fermenters that produce negligible amounts of methane. We quantified the GHG savings Australia could make if livestock were reduced on the range-lands where kangaroo harvesting occurs and kangaroo numbers increased to 175 million to produce same amount of meat. Removing 7 million cat-tle and 36 million sheep by 2020 would lower Australia's GHG emissions by 16 megatonnes, or 3% of Australia's annual emissions. However, the change will require large cultural and social adjustments and reinvestment. Trials are underway based on international experiences of managing free-ranging species. They are enabling collaboration between farmers, and if they also show benefits to sustainability, rural productivity, and conservation of bio-diversity, they could be expanded to incorporate change on the scale of this article. Farmers have few options to reduce the contribution that livestock make to GHG production. Using kangaroos to produce low-emission meat is an option for the Australian rangelands which would avoid permit fees under Australia's Emissions Trading Scheme, and could even have global application.
Les résultats des mesures de production journalière de méthane des principaux types d’herbivores à l’aide de chambres respiratoires ont permis de modéliser les émissions de méthane selon l’espèce, le stade physiologique, la composition du régime et le niveau d’alimentation. Après l’évaluation des quantités annuelles de méthane émises par les bovins en France, présentée dans un article précédent, celles émises par les ovins, les caprins et les équins ont été calculées pour chaque type d’animal à partir des apports alimentaires recommandés en tenant compte de la nature des fourrages et de la composition des régimes ingérés à chaque période de l’année.
Les émissions annuelles moyennes de méthane d’une brebis allaitante (16,7 m3) et d’une brebis laitière (17,8 m3) sont voisines de celle d’une chèvre (22,9 m3). Elles représentent respectivement 13 % de celles d’une vache allaitante ou d’une vache laitière. Celles d’une agnelle et d’une chevrette d’élevage (8 m3) sont voisines. Celle d’un agneau de boucherie élevé en bergerie avec un régime riche en aliments concentrés est le tiers de celle (2,9 m3) d’un agneau de boucherie élevé à l’herbe.
L’émission de méthane par kg de lait produit est en moyenne de 77 litres pour une brebis, 38 litres pour une chèvre et 30 litres pour une vache laitière. Par kg de carcasse produit, l’émission de méthane est en moyenne de 60 litres pour les agneaux des races laitières sevrés précocement et de 1160 litres pour les agneaux élevés sous la mère, contre 300, 580 et 1 040 litres pour les taurillons des races laitières, des races à viande et les boeufs de 40 mois (y compris la production de méthane de la mère dans le cas des races à viande).
Par kg d’aliment consommé, la production de méthane des équins est 3 à 4 fois plus faible que celle des ruminants. C’est pourquoi leurs émissions annuelles de méthane sont en moyenne de 23 à 27 m3 pour les chevaux de sport et de loisir, de 42 m3 pour les juments de trait reproductrices et de 14 à 20 m3 pour les poneys et ponettes.
Ainsi, les émissions totales annuelles de méthane par les herbivores s’élèvent à un peu plus de 2 milliards de m3, dont 91 % par les bovins, 7 % par les ovins, 1 % par les caprins et 0,6 % par les équins.
Methane emissions from a flock of 14, 1-year old sheep grazing on a grass and legume pasture were measured using a micrometeorological mass-balance method and a sulphur hexaflouride (SF6) tracer technique. The former measured the mean emission, over 45 min intervals, from all the sheep within a fenced 24 m×24 m enclosure, from the enrichment of methane (CH4) in air as it passed over the sheep. The tracer technique measured emissions from a subset of 7 individual animals over 24 h periods from measurements of CH4 and SF6 concentrations in air exhaled by the sheep, and from the known rate of release of SF6 from small permeation tubes placed in the animals’ rumens. Both methods gave highly similar results for 4 out of 5 days. When the species composition of dietary intake was steady during the last two days of measurement, the mean emission rate from the mass-balance method was 11.9±1.5 (SEM) g CH4 sheep-1 d-1, while the rate from the tracer technique was 11.7±0.4 (SEM) g CH4 sheep-1 d-1. These rates are for sheep with mean live mass of 27 kg, with a measured dry matter intake of 508 g sheep-1 d-1 and pasture dry matter digestibility of 69.5%. There was close agreement between these measurements and estimates from algorithms used to predict methane emissions from sheep for the Australian National Greenhouse Gas Inventory.
Increasing atmospheric concentrations of methane have led scientists to examine its sources of origin. Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%. Many factors influence methane emissions from cattle and include the following: level of feed intake, type of carbohydrate in the diet, feed processing, addition of lipids or ionophores to the diet, and alterations in the ruminal microflora. Manipulation of these factors can reduce methane emissions from cattle. Many techniques exist to quantify methane emissions from individual or groups of animals. Enclosure techniques are precise but require trained animals and may limit animal movement. Isotopic and nonisotopic tracer techniques may also be used effectively. Prediction equations based on fermentation balance or feed characteristics have been used to estimate methane production. These equations are useful, but the assumptions and conditions that must be met for each equation limit their ability to accurately predict methane production. Methane production from groups of animals can be measured by mass balance, micrometeorological, or tracer methods. These techniques can measure methane emissions from animals in either indoor or outdoor enclosures. Use of these techniques and knowledge of the factors that impact methane production can result in the development of mitigation strategies to reduce methane losses by cattle. Implementation of these strategies should result in enhanced animal productivity and decreased contributions by cattle to the atmospheric methane budget.