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We present results from the FAOSTAT agri-food systems emissions database, relative to 236 countries and territories and over the period 1990-2019. We find that in 2019, world-total food systems emissions were 16.5 billion metric tonnes (Gt CO2eq yr-1), corresponding to 31 % of total anthropogenic emissions. Of the agri-food systems total, global emissions within the farm gate -from crop and livestock production processes including on-farm energy use--were 7.2 Gt CO2eq yr-1; emissions from land use change, due to deforestation and peatland degradation, were 3.5 Gt CO2eq yr-1; and emissions from pre- and post-production processes -manufacturing of fertilizers, food processing, packaging, transport, retail, household consumption and food waste disposal--were 5.8 Gt CO2eq yr-1. Over the study period 1990-2019, agri-food systems emissions increased in total by 17 %, largely driven by a doubling of emissions from pre- and post-production processes. Conversely, the FAO data show that since 1990 land use emissions decreased by 25 %, while emissions within the farm gate increased only 9 %. In 2019, in terms of single GHG, pre- and post-production processes emitted the most CO2 (3.9 Gt CO2 yr-1), preceding land use change (3.3 Gt CO2 yr-1) and farm-gate (1.2 Gt CO2 yr-1) emissions. Conversely, farm-gate activities were by far the major emitter of methane (140 Mt CH4 yr-1) and of nitrous oxide (7.8 Mt N2O yr-1). Pre-and post-processes were also significant emitters of methane (49 Mt CH4 yr-1), mostly generated from the decay of solid food waste in landfills and open-dumps. The most important trend over the 30-year period since 1990 highlighted by our analysis is the increasingly important role of food-related emissions generated outside of agricultural land, in pre- and post-production processes along food supply chains, at all scales from global, regional and national, from 1990 to 2019. In fact, our data show that by 2019, food supply chains had overtaken farm-gate processes to become the largest GHG component of agri-food systems emissions in Annex I parties (2.2 Gt CO2eq yr-1). They also more than doubled in non-Annex I parties (to 3.5 Gt CO2eq yr-1), becoming larger than emissions from land-use change. By 2019 food supply chains had become the largest agri-food system component in China (1100 Mt CO2eq yr-1); USA (700 Mt CO2eq yr-1) and EU-27 (600 Mt CO2eq yr-1). This has important repercussions for food-relevant national mitigation strategies, considering that until recently these have focused mainly on reductions of non-CO2 gases within the farm gate and on CO2 mitigation from land use change. The information used in this work is available as open data at: https://zenodo.org/record/5615082 (Tubiello et al., 2021d). It is also available to users via the FAOSTAT database (FAO, 2021a), with annual updates. [ABSTRACT FROM AUTHOR]

• We apply a model coupling method to "reproduce" the field experiment process at 24 representative sites via model simulations. • The model coupling enriches and updates the rice genetic parameters. • The simulations demonstrate the feasibility of implementing water-saving irrigation methods across rice fields in China. • The expansion of "Alternate Wetting and Drying" method can lead to a "win-win" solution for the food-water-GHG emissions tradeoffs. Paddy rice cultivation is an important source of agricultural greenhouse gas emissions in China. The traditional flooded paddy rice fields not only use large amounts of irrigation water, but also produce significant methane (CH 4) emissions. To balance food security with environmental impacts of rice production, many water-saving irrigations technologies have been tested in the field to increase the drainage period during the rice growth cycle. However, whether these management solutions can be implemented at the regional scale needs to be further explored. Because it is too time-consuming and resource-intensive for field experiments to be carried out across large areas, we opt to assess the regional impacts of alternative irrigation schemes via computer modeling, by coupling the well-known DSSAT and DNDC models, which have been extensively validated in China. Irrigation methods tested include the traditional Continuous Flooding (CF), Midseason Drainage (MD) and Alternate Wetting and Drying (AWD). Simulation results show that compared with CF, water-saving irrigation methods can significantly reduce the CH 4 emission from paddy rice field, with slight or no loss in expected rice yields. AWD had the greatest effect in reducing irrigation water amounts and CH 4 emission. Compared with CF, CH 4 emission under the AWD were 60% - 71% lower in Northeast China sites and 34% - 65% lower in South China sites. At the same time, compared to CF, irrigation water use in AWD was reduced by 23% - 34% in northeast China sites and by 18% - 50% in south China sites. Our results suggest that policies that support expansion of AWD in paddy rice cultivation across China can lead to a "win-win" for the food-water-GHG emissions tradeoffs, and offer a viable solution for policy makers and stakeholders in China. [ABSTRACT FROM AUTHOR]