ReviewAGRICULTURE

Many shades of gray—The context-dependent performance of organic agriculture

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Science Advances  10 Mar 2017:
Vol. 3, no. 3, e1602638
DOI: 10.1126/sciadv.1602638
  • Fig. 1 Overall average performance of organic agriculture relative to conventional agriculture (indicated by the red circle). (A) Performance per unit area and (B) performance per unit output.

    Average organic performance is indicated by the red circle. (A) Performance per unit area and (B) performance per unit output. Figure includes production (brown petals), environmental (green petals), producer (red petals), and consumer (blue petals) benefits (petals that extend beyond the red circle) and costs (petals inside the red circle). Dimensions assessed include (starting at the top, going clockwise) production, biodiversity, soil quality, water quality, water quantity, climate change mitigation, farmer livelihoods, farmer and farm worker health, farm worker livelihoods, consumer health, and consumer access. Larger petals represent superior organic performance (for example, a larger petal for N loss means lower N loss in organic). In addition, note that per unit output performance is only relevant for environmental variables; other petals are unchanged relative to per unit area performance. Shading of petals represents level of uncertainty for each variable, with uncertainty determined by the number of primary studies included in each assessment and the level of agreement between different quantitative reviews (see fig. S6 for details). Variables that could not be quantified are in gray. Length of gray petals also varies slightly depending on whether the qualitative assessment of each dimension (see Table 2) is uncertain or suggests no difference (that is, petal is on the red circle) or shows higher (that is, petal extends beyond the red circle) or lower (that is, petal is inside the red circle) performance. Means used to quantify each variable (also known as petal length) were calculated as weighted means (weighted by the sample size, typically the number of observations in each quantitative review) across estimates of response ratios (organic/conventional) from different quantitative reviews (see table S1 for sources and figs. S1, S2, and S5 for values used) and are represented on a log scale to treat changes in the numerator and denominator the same [with the red circle indicating no change, that is, log(org/conv) = 0]. Note that this approach does not account for double-counting of primary studies included in multiple quantitative reviews or meta-analyses. This double-counting might affect petal size but would not alter qualitative size relationships among petals.

  • Fig. 2 Regional distribution of organic area, organic producers, as well as studies included in key meta-analyses on organic agriculture.

    “Organic area” represents data on total organic agricultural area (in hectares) for 2014 (3). “Organic producers” represents data for 2013 (3). “Yield studies” represents all studies (n = 210) included in the works of Seufert et al. (18), Ponisio et al. (19), and de Ponti et al. (20). “Profitability studies” represents all studies (n = 44) included in the work of Crowder and Reganold (81). “Biodiversity studies” represents all studies (n = 150) included in the works of Crowder et al. (30), Bengtsson et al. (31), and Tuck et al. (32). “SOC (soil organic carbon) studies” represents all studies (n = 75) included in the work of Gattinger et al. (39).

  • Fig. 3 Uncertainty range around the average (per unit area) performance (depicted in Fig. 1A) of organic agriculture relative to conventional agriculture (indicated by the red circle).

    (A) Lower and (B) upper uncertainty range. Figure includes production (brown petals), environmental (green petals), producer (red petals), and consumer (blue petals) benefits (petals that extend beyond the red circle) and costs (petals inside the red circle). See Fig. 1 for details on variables depicted. Shading of petals represents the level of uncertainty for each variable (see Fig. 1 for legend and fig. S6 for details). Variables that could not be quantified are shaded in gray. Upper and lower ranges represent the lowest and highest values (typically low or high confidence intervals), represented as log response ratio (organic/conventional), from different quantitative reviews or meta-analyses (see table S1 for sources and figs. S1, S2, and S5 for values used).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/3/e1602638/DC1

    Supplementary Materials and Methods

    fig. S1. Impact of organic agriculture on production, farmer livelihood, farm worker livelihood, and consumer access (as depicted in Figs. 1A and 3), as well as water quality and climate change mitigation variables per unit output (as depicted in Fig. 1B), as observed by different meta-analyses and quantitative reviews [that is, de Ponti et al. (20), Ponisio et al. (19), Seufert et al. (18), Crowder and Reganold (81), Mondelaers et al. (41), Tuomisto et al. (40), Skinner et al. (54), and Gomiero et al. (12)].

    fig. S2. Impact of organic agriculture on biodiversity, soil quality, water quality, and climate change mitigation variables per unit area (as depicted in Figs. 1A and 3), as observed by different meta-analyses and quantitative reviews [that is, Bengtsson et al. (31), Crowder et al. (30), Tuck et al. (32), Tuomisto et al. (40), Mondelaers et al. (41), Gattinger et al. (39), Skinner et al. (54), and Gomiero et al. (12)].

    fig. S3. Difference in content of individual secondary metabolites, and vitamin groups in organic versus conventional plant foods, as observed by different meta-analyses and quantitative reviews [that is, Barański et al. (102), Brandt et al. (101), Dangour et al. (104), Hunter et al. (100), and Worthington (103)].

    fig. S4. Difference in content of individual mineral micronutrients and macronutrients in organic versus conventional plant foods, as observed by different meta-analyses and quantitative reviews [that is, Barański et al. (102), Dangour et al. (104), Hunter et al. (100), and Worthington (103)].

    fig. S5. Difference in content of aggregated secondary metabolites, vitamins, mineral micronutrients and macronutrients, and pesticide residues in organic versus conventional plant foods, as observed by different meta-analyses and quantitative reviews [that is, Barański et al. (102), Brandt et al. (101), Dangour et al. (104), Hunter et al. (100), Smith-Spangler et al. (105), and Worthington (103)].

    fig. S6. Uncertainty in different variables (per unit area) on production benefits and costs (brown), environmental benefits and costs (green), producer benefits and costs (red), and consumer benefits and costs (blue), based on quantitative reviews of the organic literature.

    table S1. Sources used for variables that could be quantified in Figs. 1 and 3.

    table S2. Variables influencing the organic-conventional yield gap according to different meta-analyses [that is, Seufert et al. (18), de Ponti et al. (20), and Ponisio et al. (19)] and large-scale census data analyses [Kniss et al. (21)].

    table S3. Variables influencing the difference in biodiversity between organic and conventional agriculture according to different meta-analyses [that is, Tuck et al. (32) and Kennedy et al. (33)] and large-scale primary studies [that is, Schneider et al. (34)].

    References (127129)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • fig. S1. Impact of organic agriculture on production, farmer livelihood, farm worker livelihood, and consumer access (as depicted in Figs. 1A and 3), as well as water quality and climate change mitigation variables per unit output (as depicted in Fig. 1B), as observed by different meta-analyses and quantitative reviews that is, de Ponti et al. (20), Ponisio et al. (19), Seufert et al. (18), Crowder and Reganold (81), Mondelaers et al. (41), Tuomisto et al. (40), Skinner et al. (54), and Gomiero et al. (12).
    • fig. S2. Impact of organic agriculture on biodiversity, soil quality, water quality, and climate change mitigation variables per unit area (as depicted in Figs. 1A and 3), as observed by different meta-analyses and quantitative reviews that is, Bengtsson et al. (31), Crowder et al. (30), Tuck et al. (32), Tuomisto et al. (40), Mondelaers et al. (41), Gattinger et al. (39), Skinner et al. (54), and Gomiero et al. (12).
    • fig. S3. Difference in content of individual secondary metabolites, and vitamin groups in organic versus conventional plant foods, as observed by different meta-analyses and quantitative reviews that is, Barański et al. (102), Brandt et al. (101), Dangour et al. (104), Hunter et al. (100), and Worthington (103).
    • fig. S4. Difference in content of individual mineral micronutrients and macronutrients in organic versus conventional plant foods, as observed by different meta-analyses and quantitative reviews that is, Barański et al. (102), Dangour et al. (104), Hunter et al. (100), and Worthington (103).
    • fig. S5. Difference in content of aggregated secondary metabolites, vitamins, mineral micronutrients and macronutrients, and pesticide residues in organic versus conventional plant foods, as observed by different meta-analyses and
      quantitative reviews that is, Barański et al. (102), Brandt et al. (101), Dangour et al. (104), Hunter et al. (100), Smith-Spangler et al. (105), and Worthington (103).
    • fig. S6. Uncertainty in different variables (per unit area) on production benefits and costs (brown), environmental benefits and costs (green), producer benefits and costs (red), and consumer benefits and costs (blue), based on quantitative reviews of the organic literature.
    • table S1. Sources used for variables that could be quantified in Figs. 1 and 3.
    • table S2. Variables influencing the organic-conventional yield gap according to different meta-analyses that is, Seufert et al. (18), de Ponti et al. (20), and Ponisio et al. (19) and large-scale census data analyses Kniss et al. (21).
    • table S3. Variables influencing the difference in biodiversity between organic and conventional agriculture according to different meta-analyses that is, Tuck et al. (32) and Kennedy et al. (33) and large-scale primary studies that is, Schneider et al. (34).
    • References (127–129)

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