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: pete.smith@abdn.ac.uk

Transition: Food and Farming in 21st Century Britain, Soil Association National Conference, Bristol, 18-19th November 2008

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?

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.

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?

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?

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)

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?

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

Land use change ?

Deforestation

yield, t/ha

N applied, kg/ha0

land required, ha/tonne

Slide from Pete Berry (ADAS)

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)

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?

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)

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)

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?

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

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?

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

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

Erisman et al. (2008)

Can we replace mineral N altogether?

Erisman et al. (2008)

Can we replace mineral N altogether?

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

Thank you for your attention