1. Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences, School of Biological Sciences, University of Aberdeen, Scotland, UK E-mail: pete.smith@abdn.ac.uk Transition: Food and Farming in 21 st Century Britain, Soil Association National Conference, Bristol, 18-19 th November 2008

2. The big challenges for organic farming Can organic farming maintain productivity to feed 9 Billion people, without spreading onto more land? Is organic farming compatible with reduced livestock numbers / consumption? Can organic residues provide enough reactive N to fertilise crops sufficiently to feed 9 Billion people?

3. The role of organic agriculture – potential positives Most practices improve soil C sequestration Reduce need for mineral N fertiliser (but not eradicate it?) Reduce fossil fuel cost of manufacturing mineral N fertiliser Keep nutrient cycles tightly coupled Improve soils fertility, biodiversity etc.

4. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

5. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

6. Practices used in organic systems that can increase GHG emissions. e.g. Manure may give higher N 2 O emissions than mineral fertiliser when applied and when in storage Increased energy input from mechanical weeding compared to herbicides (even after accounting for the energy input in herbicide manufacture) Increased tillage (for mechanical weeding) may reduce soil C relative to zero tillage (difficult in organic farming)

7. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

8. Agricultural GHG emissions

9. Land use change ? Deforestation yield, t/ha N applied, kg/ha0 land required, ha/tonne Slide from Pete Berry (ADAS)

10. Effects of land use change Ecosystem typeIPCC (t CO 2 /ha)Searchinger et al. (2008) (t CO 2 /ha) Tropical Forest553-824604-824 Temperate forest 297-627688-770 Tropical grassland and savannah 189-21475-305 Temperate grasslands 139-242111-200 Wetlands7481146 Figures are calculated over a 30 year period Slide from Pete Berry (ADAS)

11. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

12. Livestock Accounts for 9 percent of CO 2 Generates 65 percent of human-related nitrous oxide (mostly from manure). Accounts for respectively 37 percent of all human- induced methane (and 64 percent of ammonia, which contributes significantly to acid rain). Primary consumption of crops (by humans) is more efficient than feeding to livestock and then consuming the livestock / products FAO (2006)

13. Agricultural GHG emissions CH 4 and N 2 O emissions by world region, 1990-2020 Agriculture - 5.1 to 6.1 GtCO 2 -eq/yr in 2005 (10-12% of total global anthropogenic emissions of GHGs). CH 4 contributes 3.3 GtCO 2 -eq/yr and N 2 O 2.8 GtCO 2 -eq/yr. Of global anthropogenic emissions in 2005, agriculture accounts for about 60% of N 2 O and about 50% of CH 4. Smith et al. (2007)

14. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

15. Are we actually sequestering carbon or just moving it about? Organic farm Conventional farm Manure Mineral N More manure here….but……..less manure here Effect over the whole cropland area = zero

16. The role of organic agriculture – potential negatives Some practices less compatible with those that improve soil C sequestration – some increase GHG emissions Unless productivity can be maintained, more land could be required for agriculture – sometimes called displacement / leakage – disastrous for soils and climate Can we reduce animal numbers under organic farming? Applying manure in organic systems – this would be applied elsewhere anyway (in non-organic systems) – so is this genuine C sequestration? Can we maintain productivity increases without mineral N? To do so, do we need better cultivars with improved N use efficiency? If so, do we need GM?

17. Recorded and projected population (o) and grain production ( ) (adapted from Dyson, 1996) Slide from Peter Gregory, SCRI

18. World cereal yield and area harvested per capita (extended from Dyson, 1996) Slide from Peter Gregory, SCRI

19. Erisman et al. (2008) Can we replace mineral N altogether?

20. Erisman et al. (2008) Can we replace mineral N altogether?

21. Personal perspectives I grow my own fruit and veg. organically I usually buy organic produce but… –…I also want to buy fair trade food –…I try to buy from my local farm shop – they are not organic farmers but are part of the small rural community where I live – I want to support them I am vegetarian – much more efficient and less GHG per unit product. Consuming much less meat would be environmentally beneficial – reduces the organic manures available for organic farming There are multiple drivers (economic, cultural, societal, scientific, ideological) that determine our choices in the developed world - farmers / consumers in developing countries have very little choice I would hate to see us simply export our emissions In my opinion, organic agriculture might be part of the solution, but is not the solution

22. Thank you for your attention