Does organic farming reduce environmental impacts?

Transcription

1 Does organic farming reduce environmental impacts? Improving health worldwide Dr Hanna Tuomisto London School of Hygiene & Tropical Medicine

2 Introduction Organic farming aims at reducing negative environmental impacts IFOAM standards state: organic agriculture should fit the cycles and balances in nature without exploiting it by using local resources, recycling, reuse and efficient management of materials and energy Aim of the study was to review the finding of studies comparing environmental impacts of organic and conventional farming

3

4 Selection criteria of the papers Literature search terms: [organic AND conventional AND farming] OR [organic AND conventional AND agriculture] All papers published before 26th September 2009 i) the study was related to European farming systems, ii) the study compared organic and conventional farming and provided quantitative results at least one of the following aspects: soil organic carbon, land use, energy use, GHG emissions, eutrophication potential, acidification potential, nitrogen leaching, phosphorus losses, ammonia emissions or biodiversity, iii) the paper was published in a scientific peer-reviewed journal 109 papers included

5 A Non-LCA impacts per unit of field area B Non-LCA impacts per unit of product N = 10 * Response ratio 0.0 Response ratio 3 2 N = 10 ns -0.5 N=56 N= ** N=19 N=11 ns ns * N=48 ** N leaching Nitrous oxide Ammonia P losses SOM nitrogen N emissions 2 O ammonia phosphorus emissions leaching 0-1 N leaching per product Nitrous oxide unit emissions per product unit N = 10 ns Ammonia emissions nitrogen nitrous oxide ammonia per product unit leaching emissions emissions Median response ratios, quartiles, extreme values and outliers (O = and > 3 box lengths from the upper or lower edge of the box) for non-lca (Life Cycle Assessment) impacts (A): soil organic matter (SOM), phosphorus (P) losses, nitrogen (N) leaching, nitrous oxide emissions per unit of area and ammonia emissions per unit of area; and LCA impacts: energy use, greenhouse gas emissions (GHG), acidification potential (AP), eutrophication potential (EP) and land use (LU) per product unit. (+ impacts from organic farming are higher, - impacts from organic farming are lower, N=number of cases in the sample, ns=not significantly different from zero P>0.05, **P<0.01, *P<0.05)

6 LCA impacts per unit of product Land use response ratio Greenhouse gas response ratio milk cereals beef pork other crops olive milk cereals beef pork other crops

7 Soil organic matter 0.6 SOM response ratio N = 4 ns N = 36 ** N = 6 * organic less organic more same Response ratios for soil organic matter (SOM) when cases are grouped based on the relative manure inputs between the systems.

8 Yields N Min Max Mean SD Winter wheat Spring wheat Barley Oat Other cereals Potato Vegetables Sugar beet Leys Olive Citrus Melons Oilseed rape Relative minimum, maximum and mean yields (organic/conventional), standard deviation of the means (SD) and number of cases (N).

9 Biodiversity impacts Relative impact of organic (number of studies) Taxon positive negative no difference Birds Mammals Butterflies Spiders Earthworms Beetles Other arthropods Plants Soil microbes TOTAL

10 CONCLUSIONS

11 Summary of the results Allocation unit Unit of field area Unit of product 1) Nitrogen leaching +++ 2) Phosphorus losses +/- 3) Soil organic matter + 4) Ammonia emissions ) Nitrous oxide emissions ) Energy use ++ 7) Greenhouse gas emissions +/- 8) Acidification potential - 9) Land use ) Eutrophication potential ) Biodiversity +++ A summary of the results of the meta-analysis comparing environmental impact of organic farming on environment (the symbols are based on the median response ratios of each indicator as follows: <-0.30 (+++), (++), (+), (+/-), (-), (--), >0.30 (---), for biodiversity indicator the symbol presents the ratio of studies showing positive impacts from organic farming)

12 Recommendations High yields important also from the environmental point of view Challenge to improve yields without harming the environment Nutrient management a key Farming systems that combine the best practices from organic and conventional farming may lead in the optimal result. The optimal system depends on the circumstances

13 THANK YOU Improving health worldwide

14 References Tuomisto et al Does organic farming reduce environmental impacts? A meta-analysis of European research. Journal of Environmental Management, 112, Photos: freeimages.com