Can soil and tree carbon sequestration maintain zero net emissions grazing?

Context Goals set by countries and corporate entities in response to the Paris climate agreement (COP21) have put a focus on livestock producers to reduce greenhouse gas emissions (GHGe). However, methods to reduce emissions in livestock enterprises are limited. One option to reduce the balance of GHGe produced on farms is to sequester carbon in soils and trees within the farm boundary. Aims To assess the effectiveness of carbon sequestration in maintaining net zero emissions on a grazing enterprise (Jigsaw Farms). A previous study indicated that a single property in this enterprise (Hensley Park) achieved net zero status in 2014. Methods Net emissions produced by the enterprise across two properties (Melville Forrest and Hensley Park) were estimated by calculating on-farm and pre-farm emissions, using the IPCC-approved method, SB-GAFv2.3, FullCAM, and soil data provided by Jigsaw Farms. Emissions and vegetation sequestration results were validated through field data and farm records. Key results From 2010 to 2014, Jigsaw Farm’s Hensley Park property sequestered more carbon in trees and soils than the equivalent GHGe produced. Trees, on average, provided 89% of the sequestration and soils provided 11%. After this, an increase in GHGe from higher animal numbers and declining sequestration rates meant the enterprise was no longer net zero. Emissions in 2021 were 10,870 t carbon dioxide equivalents (CO2-e), while vegetation sequestered 6704 t CO2-e. Data was insufficient to assess soil carbon sequestration. Although net emissions increased, the emissions intensity of products was halved due to sequestration. Conclusions Although increased woody vegetation on-farm enabled achievement of net zero emissions, maintaining this position using only sequestration has proven challenging. Other on-farm benefits of trees and shrubs, such as shade and shelter for animals from climatic extremes, conservation and aesthetic benefits, are important in decisions to integrate trees. Implications The level of emission reduction achieved by trees can be increased, and the period of emissions reduction extended, by expanding tree plantings, staging plantings over time, using faster-growing species or, in the longer term, harvesting trees for timber and accounting for carbon stored in long-lived products. However, relying on sequestration alone cannot indefinitely meet net zero emission objectives.