Carbon Sequestration in European Agricultural Soils

by 2010 - Potential, Uncertainties, Policy Impacts 

Annette Freibauer[afreib@bgc-jena.mpg.de]

Mark D. A. RounsevellPete Smith

Jan VerhagenUCL

Vleeshouwers & Verhagen, GCB 2002

C fluxes in SOC in the 1st commitment period: BAU

t C ha-1 y-1

Croplandmean flux: +0.83 (0.40) t C ha-1 y-1 (source)Total in EU-15: 77 (37) Tg C y-1

Grasslandmean flux: -0.60 (0.65) t C ha-1 y-1 (sink?)Total in EU-15: -30 (32) Tg C y-1

Total agricultural soilsTotal in EU-15: 48 (37) Tg C y-1 (source)

Most promising measures

1 Promote organic input on arable land instead of grassland (crop residues, cover crops, FYM, compost, sewage sludge)

2 Permanent revegetation of arable set-aside land (e.g. afforestation) or extensivation of arable production by introduction of perennial components

3 Biofuel production with short-rotation coppice plantations and perennial grasses on arable set-aside land

4 Promote organic farming

5 Promote permanently shallow water table in farmed peatland

6 Zero tillage / conservation tillage

Organic input

Reduced tillage

Extensification

Bioenergy crops

Organic farming

Longer leys

Permanent grass

Peatlands

t C-e

qu. h

a-1 y

-1

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.05.0

6.0

CO2

CH4

N2O

Cropland Grassland Peatland

Potential per unit area

Uncertainty: spatial variability, soil and climate types; no human components

Factors limiting carbon sequestration

Sink saturation

Non-permanence

Availability of land and resources

Adoption of measures / contiguous?

Area and resources available

total area limitations suitable area million ha million ha

Cropland 73 more organic input organic material ~60? reduced tillage climate, soil 63? extensification, perennials set-aside land 7.3 bioenergy crops set-aside land 7.3 organic farming now 2% of cropland 7

Grassland (in rotation) 8.4 longer duration of leys no need: set-aside 7.3 from leys to permanent grass no need: set-aside 7.3 Peatland in agriculture 3.6 restoration of drained soil highly productive <1-2

Ramsar, CBD!

Uncertainty: adoption rate, adoption time?

Organic input

Reduced tillage

Extensification

Bioenergy crops

Organic farming

Longer leys

Permanent grass

Restoration

Tg

C-e

qu. y

-1 in

EU

-15

0

1

2

3

4

5

6

7

8

C sequestrationGHG reduction

Cropland Grassland Peatland

Feasible Potential in EU-15

Uncertainty: spatial variability, adoption, permanence of adoption

Environmental effects

Tillage Amendments Extensif. Peatland

Herbizides, pestizides

Non-CO2 gases

NH3, NOx

Biodiversity

Water quality

Soil quality

Sustainable land management

Productivity?

?

?

?

?

Farm incomeOrganic amendments positive long-term, easy, cheap

Bioenergy crops region-specific, emerging marketsOrganic farming region-specific, emerging markets

Reduced tillage region-specific, risks, long-term benefits

Extensification region-specific, compensation payments?Peatland restoration region-specific, compensation payments?

• Judgements about farm incomes are always qualified by location – we cannot generalise!

• different soil types, climates and farm structures • A modelling approach to address this problem and to

provide better quantification?

Policy impacts

Putting C sequestration options into a real-world context influenced by policy

Policy effects(post 1990)

Other effects

Land usechange

C sequestrationpotential

Policy changes post 1990

• Radical changes in the structure of the CAP driven by the 1992 MacSharry reforms and Agenda 2000

• From production-based price support to area payments and set-aside

• A wealth of rural development and agri-environmental policies

Policy effects on land use

• Market support (intervention, import duties) that maintain producer prices

• Production controls - quota: number of dairy cows declining - set aside: C sequestration, biofuels

• Direct aid payments (arable area, agri-environment)- change in permanent crop production systems- maintenance of meadows in LFA- forestation of agricultural land

Conclusions (1)

• Policy changes post 1990 have probably had an overall +ve effect on C sequestration

• But, uncertainties surround the effects of some policies (LFAs, NVZs, organic) and their impacts on farm incomes

• Policy could contribute further to soil C sequestration in Europe

• Further research should target policy as well as management options, be geographically explicit and tackle impacts on farm incomes

Conclusions (2): Caveats

C balance in grasslands?

What measures are best adjusted to regional management preferences?

Regional land use / land management historyRegional best practice

Permanent, contiguous, long-term adoption of measures?Monitoring!Costs?

Regional modelling for potential, adoption, income necessary

Regional refinement of policy measures necessary

Availability of land and resources / potential

Soil carbon sequestration (Mt CO2 y-1) Measure Limiting factor Theoretical Technical Economic?

all agric. Given feasible land used limitation by 2012

Cropland Zero-tillage Suitable land = 63 Mha 103 89.28 8.93 Reduced-tillage Suitable land = 63 Mha < 103 <89.28 <8.93

Set-aside <10% of arable; < 7.3 Mha 103 Max = 8.93 0 Perennial grasses and permanent crops No incentives to grow more 165 0? 0? Deep-rooting crops Research and breeding

needed for annual crops 165 0? 0? Animal manure Manure avail. = 385 Mt dm y-1 100 86.83 ? Crop residues Surplus straw = 5.3 Mt dm y-1 185 90.46 ? Sewage sludge Sewage sludge = 71 Mt dm y-1 69 6.30 ? Composting Compost available at present

= 160 t dm y-1 (8 M ha) 100 11 11? Improved rotations 0 >0 0? Fertilisation 0 0 0 Irrigation 0 0 0

Bioenergy crops only current set-aside = 7.3 Mha 165 16.52 3.3 Extensification current set-aside to extensify

30% of arable agr. = 20 Mha 144 41.63 ? Organic farming Could increase to 10% = 7.3 Mha 0-144 14.40 14.4

Availability of land and resources / potential

Soil carbon sequestration (Mt CO2 y-1) Measure Limiting factor Theoretical Technical Economic?

all agric. Given feasible land used limitation by 2012

Grassland ? Knowledge! ? ? ?

Revegetation

Abandoned arable land current set-aside = 7.3 Mha 165 16.52 Max. 16.52

Land conversion Arable to woodland current set-aside = 7.3 Mha 165 16.52 Max. 16.52 Arable to grassland current set-aside = 7.3Mha 140 14 0 Grassland to Land-use change since 1990 arable calculated as 2.7 Mha -266 -10 (since 1990) Future = 0 Permanent crops Land-use change since 1990 to arable calculated as 0.4 Mha -42.5 -1.46 (since 1990) 0 Woodland to Negligible land-use change arable since 1990 =>-266 0 0

Availability of land and resources / potential

Soil carbon sequestration (Mt CO2 y-1) Measure Limiting factor Theoretical Technical Economic?

all agric. Given feasible land used limitation by 2012

Farmed organic soils Protection and Assuming all cultivated restoration organic soils are restored >36 >36 >36 Avoid row crops and tubers No incentive 0 GHG: 2 0? 0? Avoid deep ploughing No incentive 3 GHG: 3 0? 0? More shallow Possibly attractive on grass- water table land when new melioration

is needed = 50 % of grass- 36 GHG: 36 15 15 land area = 1.5 Mha Convert arable to grassland No incentive 3 GHG: 3 0? 0? Convert arable Subsidies compensate income to woodland losses: adoption rate max. 2 GHG: 3 1 1

50 % of arable area = 0.3 Mha

Non-CAP effects• Technological change (plant & animal breeding)• World markets & international trade agreements• Changing consumer preferences – less meat, shifts

from olive to sunflower oil, etc.• Opportunity costs of labour, i.e. competition with

other sectors• Land degradation (e.g. erosion)• Irrigation water availability and quality• Education and information dissemination