UWA School of Agriculture & Environment, University of Western Australia, MO87/35 Stirling Highway, Crawley, Western Australia 6009, Australia.
UWA School of Agriculture & Environment, University of Western Australia, MO87/35 Stirling Highway, Crawley, Western Australia 6009, Australia.
Animal. 2022 Apr;16(4):100490. doi: 10.1016/j.animal.2022.100490. Epub 2022 Mar 18.
Greenhouse gas emissions from Western Australia's sheep flock account for 26% of the state's agricultural emissions, principally as a result of enteric methane emissions. A decrease in emissions between 2005 and 2019 can be partly explained by a 44% drop in sheep numbers over that period, but less is known about potential changes in the methane intensity of sheepmeat and wool kg CO equivalents/kg product. Using the livestock systems modelling software GrassGro™, we assessed the changes in methane intensity of sheepmeat and wool produced in two major sheep-producing regions in Western Australia. We also evaluated a series of future scenarios. Our results demonstrate that the observed emissions reductions are largely a result of a decrease in flock size, although methane intensity has also decreased somewhat by 11.1%. Simulation of future trajectories indicates that methane intensity could be as much as 18.8% lower by 2030, compared to 2005, with further reductions of up to 42% considered possible. The primary driver of the decreased methane intensity to date is increased flock reproductive performance through increased marking rates, higher rates of ewe lamb mating, and lower ewe death rates. However, despite reductions in methane intensity per kg of product, net emissions per ewe have risen 11.6% since 2005 and are forecast to rise by up to 21.8% by 2030, with potential further increases of up to 61% considered possible. This is driven by increased feed intake due to an increased number of lambs produced per ewe, higher ewe standard reference weights, and lower ewe death rates. Therefore, achieving absolute net reductions in the methane emissions through productivity improvements is unlikely to be prospective. Reducing net emissions is instead likely to be contingent on a reduction in flock numbers, breakthroughs in anti-methanogenic research, or via emissions offsetting. Our approach can be applied in other major livestock producing regions to evaluate emissions performance, with potential implications for agricultural and trade policy as markets increasingly seek lower emissions product.
澳大利亚西部绵羊群的温室气体排放占该州农业排放量的 26%，主要是由于肠道甲烷排放。2005 年至 2019 年期间排放量的下降部分可以归因于该期间绵羊数量下降了 44%，但对羊肉和羊毛公斤二氧化碳当量/公斤产品甲烷强度的潜在变化了解较少。使用牲畜系统建模软件 GrassGro™，我们评估了澳大利亚两个主要绵羊生产地区生产的羊肉和羊毛的甲烷强度变化。我们还评估了一系列未来情景。我们的结果表明，观察到的排放量减少主要是由于羊群规模的减少，尽管甲烷强度也略有下降了 11.1%。未来轨迹的模拟表明，到 2030 年，与 2005 年相比，甲烷强度可能降低 18.8%，而进一步降低 42%是可能的。迄今为止，甲烷强度降低的主要驱动因素是通过提高标记率、提高母羊配种率和降低母羊死亡率来提高羊群繁殖性能。然而，尽管每公斤产品的甲烷强度有所降低，但每只母羊的净排放量自 2005 年以来增加了 11.6%，预计到 2030 年将增加 21.8%，最多可能增加 61%。这是由于每只母羊生产的羔羊数量增加、母羊标准参考体重增加和母羊死亡率降低导致饲料摄入量增加所致。因此，通过提高生产力实现甲烷排放量的绝对净减少不太可能实现。减少净排放量可能取决于羊群数量的减少、反甲烷研究的突破，或通过排放抵消。我们的方法可以应用于其他主要的牲畜生产地区，以评估排放绩效，随着市场越来越多地寻求低排放产品，这可能对农业和贸易政策产生影响。
