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![Page 1: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/1.jpg)
Can organic farming save the world?
Pete Smith
Royal Society-Wolfson Professor of Soils & Global ChangeInstitute of Biological & Environmental Sciences,School of Biological Sciences, University of Aberdeen, Scotland, UKE-mail: [email protected]
Transition: Food and Farming in 21st Century Britain, Soil Association National Conference, Bristol, 18-19th November 2008
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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?
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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.
![Page 4: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/4.jpg)
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?
![Page 5: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/5.jpg)
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?
![Page 6: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/6.jpg)
Practices used in organic systems that can increase GHG emissions. e.g.
• Manure may give higher N2O 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)
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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?
![Page 8: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/8.jpg)
Agricultural GHG emissionsGlobal contribution of Agriculture to Greenhouse
gas emissions
10 -12 %
0.6-1.2 %
6-17 %
17-30 %
0
5
10
15
20
25
30
35
Direct methaneand nitrous oxide
emissions
Fertilisersproduction and
distribution
Land conversionto agriculture
Total
Pg
CO
2-eq
yr
-1
Series1
of global GHG emissions %
Pg CO 2-eq yr-1
% of global GHG emissions
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Land use change ?
Deforestation
yield, t/ha
N applied, kg/ha0
land required, ha/tonne
Slide from Pete Berry (ADAS)
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Effects of land use change Ecosystem type IPCC (t CO2/ha) Searchinger et al.
(2008) (t CO2/ha)
Tropical Forest 553-824 604-824
Temperate forest
297-627 688-770
Tropical grassland and savannah
189-214 75-305
Temperate grasslands
139-242 111-200
Wetlands 748 1146Figures are calculated over a 30 year period
Slide from Pete Berry (ADAS)
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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?
![Page 12: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/12.jpg)
Livestock
• Accounts for 9 percent of CO2
• 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)
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Agricultural GHG emissions
CH4 and N2O emissions by world region, 1990-2020
• Agriculture - 5.1 to 6.1 GtCO2-eq/yr in 2005 (10-12% of total global anthropogenic emissions of GHGs). • CH4 contributes 3.3 GtCO2-eq/yr and N2O 2.8 GtCO2-eq/yr. • Of global anthropogenic emissions in 2005, agriculture accounts for about 60% of N2O and about 50% of CH4. Smith et al. (2007)
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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?
![Page 15: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/15.jpg)
Are we actually sequestering carbon or just moving it about?
Organic farm Conventional farm
Manure Manure Mineral N
More manure here….but……..less manure here
Effect over the whole cropland area = zero
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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?
![Page 17: Can organic farming save the world? Pete Smith Royal Society-Wolfson Professor of Soils & Global Change Institute of Biological & Environmental Sciences,](https://reader035.fdocuments.net/reader035/viewer/2022062511/55163d9b550346a2308b652b/html5/thumbnails/17.jpg)
Year
1920 1940 1960 1980 2000 2020 2040
Popula
tion (bill
ion)
0
2
4
6
8
Gra
in p
roduct
ion (M
t)
0
500
1000
1500
2000
Recorded and projectedpopulation (o) and grain production ()
(adapted from Dyson, 1996)
Slide from Peter Gregory, SCRI
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World cereal yield and area harvested per capita (extended from Dyson, 1996)
Year
1960 1970 1980 1990 2000 2010
Ave
rag
e c
erea
l yie
ld (
t ha-1
)
1.0
1.5
2.0
2.5
3.0
3.5
Are
a (h
a)
per
capi
ta
0.10
0.12
0.14
0.16
0.18
0.20
0.22
Slide from Peter Gregory, SCRI
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Erisman et al. (2008)
Can we replace mineral N altogether?
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Erisman et al. (2008)
Can we replace mineral N altogether?
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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
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Thank you for your attention