Agriculture is both a contributor to climate change through greenhouse gas emissions and an economic sector that is heavily impacted. In terms of individual greenhouse gases, pre-shipment crop and livestock production is responsible for more than 50% of all anthropogenic methane (CH4) emissions and 75% of all nitrous oxide (N2O) emissions. Combined with emissions from pre- and post-production activities such as fertilizer production, food transportation, processing, retailing, and waste disposal, it has been estimated that the total greenhouse gas emissions of the food system as a whole are about 20-40% or one-third of the total anthropogenic emissions. There is a need to reduce the emissions of the entire food system by reducing demand through behavioral changes in food selection and consumption patterns, and by reducing the burden on the supply side.

According to a recent paper published in Environmental Research Letters by researchers from the Food and Agriculture Organization of the United Nations (FAO), New York University, Cornell University and others, quantification of greenhouse gas emissions from crop and livestock production activities and land use change has been attempted in the past, but it has not been possible to date. However, estimates of emissions at different stages of the food system have been inadequate and have hindered the effective implementation of climate change mitigation measures at the national and regional levels. For example, the National GHG inventory (NGHGI) used by the Intergovernmental Panel on Climate Change (IPCC) for the agricultural sector only counts emissions other than carbon dioxide at the pre-shipment stage. The NGHGI only counts non-carbon dioxide emissions at the pre-shipment stage and does not include estimates of carbon dioxide emissions from sources such as organic soils, farm energy use, rainforest deforestation, and peatland fires. Instead, NGHGI has counted carbon dioxide related emissions in the land use, land use change and forestry (LULUCF) category, which tends to underestimate emissions from the food system.

The UN Food System Summit and COP26 (Conference of the Parties to the United Nations Framework Convention on Climate Change) scheduled for 2021 will require data that will help countries develop specific strategies for mitigating climate change in the food system. The paper builds on existing data to create a taxonomy that makes IPCC's Greenhouse Gas Inventory (NGHGI) and food system activities comparable. Specifically, the paper quantified the greenhouse gas emissions of carbon dioxide, methane, and nitrous oxide for the period 1990-2018 for each of the following stages: farm gate, land use change, and pre- and post-production.

The authors estimated that in 2018, greenhouse gas emissions in terms of carbon dioxide equivalent from the food system increased by 8% from 1990 to 16 gigatons (16 Gt CO2eq yr-1 metric tons), representing about one-third of anthropogenic greenhouse gas emissions. Three-quarters of these emissions (13 Gt CO2eq yr-1) were attributed to the pre-shipment and pre- and post-production process stages, with the remainder coming from land use change due to conversion of natural ecosystems to agricultural land. Emissions from total and post-production processes tend to be higher in developed countries than in developing countries. Land use change is the single largest source of emissions, but it has decreased by 30% since 1998. Domestic food transport, on the other hand, has risen 80% since 1990 and tripled, especially in developing countries. Fossil fuel emissions from the supply chain have also increased by 50% since 1990. Due to the increase in world population, per capita emissions have decreased from 2.9 tons to 2.2 tons of carbon dioxide equivalent, but per capita emissions in developed countries (3.6 tons) were twice as high as in developing countries. Compared to this method of estimation, the IPCC's usual classification underestimates food system-derived emissions due to anthropogenic greenhouse gas emissions, revealing the need for proper data development for strategy formulation at the national level.

On May 12, 2021, the Ministry of Agriculture, Forestry and Fisheries (MAFF) formulated the "Green Food System Strategy" to achieve both productivity improvement and sustainability of food, agriculture, forestry and fisheries through innovation. The strategy aims to achieve carbon neutrality by 2050 by focusing on achieving the SDGs model and realizing a green society through decarbonization of the food, agriculture, forestry and fisheries industries, and reducing the environmental impact of chemical pesticides and fertilizers. JIRCAS also aims to contribute through science and technology to solving the global issue of food system transformation, which will enable both productivity improvement and sustainability.

Reference
Francesco N Tubiello et al, Greenhouse gas emissions from food systems: building the evidence base, Environmental Research Letters (2021). DOI: 10.1088/1748-9326/ac018e
https://iopscience.iop.org/article/10.1088/1748-9326/ac018e

Contributor: IIYAMA Miyuki (Director, Information Program)