Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Melbourne, Victoria, Australia.
Sustainable Farms, Fenner School of Environment and Society, The Australian National University, Canberra, Australian Capital Territory, Australia.
Glob Chang Biol. 2022 Aug;28(15):4701-4712. doi: 10.1111/gcb.16237. Epub 2022 Jun 7.
Agricultural practices have created tens of millions of small artificial water bodies ("farm dams" or "agricultural ponds") to provide water for domestic livestock worldwide. Among freshwater ecosystems, farm dams have some of the highest greenhouse gas (GHG) emissions per m due to fertilizer and manure run-off boosting methane production-an extremely potent GHG. However, management strategies to mitigate the substantial emissions from millions of farm dams remain unexplored. We tested the hypothesis that installing fences to exclude livestock could reduce nutrients, improve water quality, and lower aquatic GHG emissions. We established a large-scale experiment spanning 400 km across south-eastern Australia where we compared unfenced (N = 33) and fenced farm dams (N = 31) within 17 livestock farms. Fenced farm dams recorded 32% less dissolved nitrogen, 39% less dissolved phosphorus, 22% more dissolved oxygen, and produced 56% less diffusive methane emissions than unfenced dams. We found no effect of farm dam management on diffusive carbon dioxide emissions and on the organic carbon in the soil. Dissolved oxygen was the most important variable explaining changes in carbon fluxes across dams, whereby doubling dissolved oxygen from 5 to 10 mg L led to a 74% decrease in methane fluxes, a 124% decrease in carbon dioxide fluxes, and a 96% decrease in CO -eq (CH + CO ) fluxes. Dams with very high dissolved oxygen (>10 mg L ) showed a switch from positive to negative CO -eq. (CO + CH ) fluxes (i.e., negative radiative balance), indicating a positive contribution to reduce atmospheric warming. Our results demonstrate that simple management actions can dramatically improve water quality and decrease methane emissions while contributing to more productive and sustainable farming.
农业实践在全球范围内创造了数千万个小型人工水体（“农场水坝”或“农业池塘”），为家畜提供用水。在淡水生态系统中，由于肥料和粪肥径流促进甲烷产生——一种极其强效的温室气体，农场水坝每平方米产生的温室气体（GHG）排放量位居前列。然而，管理策略仍在探索中，以减少数以百万计的农场水坝的大量排放。我们检验了一个假设，即安装围栏将牲畜排除在外可以减少养分、改善水质并降低水生温室气体排放。我们在澳大利亚东南部跨越 400 公里的范围内进行了一项大规模实验，在 17 个农场内比较了无围栏（N=33）和有围栏（N=31）的农场水坝。有围栏的农场水坝记录的溶解氮减少了 32%，溶解磷减少了 39%，溶解氧增加了 22%，扩散甲烷排放量减少了 56%。我们发现农场水坝管理对扩散二氧化碳排放和土壤中的有机碳没有影响。溶解氧是解释水坝之间碳通量变化的最重要变量，溶解氧从 5 毫克/升至 10 毫克/升增加一倍，会导致甲烷通量减少 74%，二氧化碳通量减少 124%，以及 CO -eq（CH + CO ）通量减少 96%。溶解氧非常高（>10 毫克/升）的水坝从正 CO -eq 变为负（CO + CH ）通量（即负辐射平衡），表明对减少大气变暖有积极贡献。我们的研究结果表明，简单的管理措施可以显著改善水质并减少甲烷排放，同时有助于更具生产力和可持续性的农业发展。
