Fig. 2. Externality costs of alternative production systems against land cost for five externalities in four agricultural sectors.
All costs are expressed per tonne of production (so land cost, for instance, is in ha-years/tonne– i.e. the inverse of yield). Different externalities are indicated by background shading (grey = GHG emissions, blue = water use, pink = N emissions, purple = P emissions, buff = soil loss), and different sectors (Asian paddy rice, European wheat, Latin American beef, European dairy) are shown by icons. Points on plots derived from multi-site experiments (a, b, c) and LCAs (e) show values for systems adjusted for site and study effects via GLMMs of land cost and externality cost (for 95% confidence intervals, see Supplementary Fig. 1), while arrows show management practices with statistically-significant effects (whose 95% confidence intervals do not overlap zero in the GLMMs; Methods). In d (wheat and N emissions), progressively darker circles depict increasing nitrate application rate (0, 48, 96, 144, 192, 240 and 288 kg N/ha-year). In f (beef and GHG emissions, estimated by RUMINANT), different colours show different system types. In g-j (dairy and four externalities), circles and squares show results for conventional and organic systems, respectively (detailed in Supplementary Table 4). Spearman's rank correlation coefficients (p-values) are a. rice-rice: -0.51 (0.002), rice-cereal: -0.36 (0.06), b. 0.19 (0.26), c. -0.34 (0.14), d. -0.21 (0.66), e. 0.95 (0.001), f. 0.83 (< 0.001), g. 0.90 (0.08), h. 0.70 (0.23), i. 1.00 (0.02) and j. 1.00 (0.02). Note that these correlation coefficients do not necessarily reflect non-linear relationships (e.g., d) accurately.