How we manage farming and food systems to meet rising demand is pivotal to the future of biodiversity. Extensive field data suggest impacts on wild populations would be greatly reduced through boosting yields on existing farmland so as to spare remaining natural habitats. High-yield farming raises other concerns because expressed per unit area it can generate high levels of externalities such as greenhouse gas (GHG) emissions and nutrient losses. However, such metrics underestimate the overall impacts of lower-yield systems, so here we develop a framework that instead compares externality and land costs per unit production. Applying this to diverse datasets describing the externalities of four major farm sectors reveals that, rather than involving tradeoffs, the externality and land costs of alternative production systems can co-vary positively: per

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New agricultural technologies bring multiple impacts which are hard to predict. Two changes taking place in Indian agriculture are a transition from bullocks to tractors and an associated replacement of manure with synthetic fertilisers. This paper uses primary data to model social, environmental and economic impacts of these transitions in South India. It compares ploughing by bullocks or tractors and the provision of nitrogen from manure or synthetic urea for irrigated rice from the greenhouse gas (GHG), economic and labour perspective. Tractors plough nine times faster than bullocks, use substantially less labour, with no significant difference in GHG emissions. Tractors are twice as costly as bullocks yet remain more popular to hire. The GHG emissions from manure-N paddy are 30 % higher than for urea-N, largely due to the organic matter in manure driving methane emissions. Labour use is significantly higher for manure, and the gender balance is more equal. Manure is substantially more expensive as a source of nutrients compared to synthetic nutrients, yet remains popular when available. This paper demonstrates the need to take a broad approach to analysing the sustainability impacts of new technologies, as trade-offs between different metrics are common.

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Rice feeds more people than any other crop, but each kilogram of rice is responsible for substantially more greenhouse gas (GHG) emissions than other key staple foods. The System of Rice Intensification (SRI) has recently received considerable attention for its ability to increase yields while using less water. Yet so far there has been little research into the GHG emissions associated with SRI production systems, and how they compare to those from conventional flooded-rice production techniques. A streamlined Life Cycle Assessment (LCA) methodology was used to compare the GHG emissions and groundwater use from SRI and from conventional rice production. Input data were derived from farmer questionnaires in SE India and appropriate secondary data sources. The results showed that SRI methods substantially raised farmers' yields, from 4.8 tons to 7.6 ton per hectare, a 58% increase, while reducing water applications. At the same time it was seen that SRI management offered opportunities for significant GHG reductions, both per hectare and per kilogram of rice produced. These savings principally arise from reduced methane emissions and reduced embodied emissions in the electricity used to pump water for irrigation. SRI nitrous oxide emissions were somewhat higher than on control farms, but the difference was significant only per hectare, not per kg of rice. The net effects of SRI practice on reducing global warming potential were positive in that the small increases in N2O did not offset the larger diminishment of CH4.