Carbon Sequestration in European Agricultural Soils by Potential, Uncertainties, Policy Impacts

Transcription

1 Carbon Sequestration in European Agricultural Soils by Potential, Uncertainties, Policy Impacts Annette Freibauer I.A. Janssens Mark D. A. Rounsevell Pete Smith Jan Verhagen

2 Outline 1 Brief outline of CarboEurope 2 C balance of European biosphere 3 Potential for C sequestration and associated uncertainties 4 Environmental side effects, other greenhouse gases 5 Technical and economic barriers - feasibility 6 Putting C sequestration in climate perspective 7 From science to policy: ECCP, ETAP

3 CarboEurope The problem The aim The people The way we work Some results The future

4 Who is CarboEurope? Total number of senior scientists: 124 Italy 17 Germany 20 Israel 1 Norway 1 Poland 1 Austria 2 Ireland 2 Spain Switzerland 2 2 Portugal 2 Belgium 3 Hungary 4 Russia 4 Czech Rep. 5 Denmark 5 Finland 5 UK 16 France 13 Netherlands 12 Sweden 7 Funded and coordinated by the European Commission DG XII Research

5 The way CarboEurope works 1000 km Upscaling 10 km µm dm Prediction ha Downscaling Verification

6 Janssens et al., 2003, Science 300(5625): Europe, Biospheric C Balance A: inclusion of uncertainty in fossil fuel emissions B: correcting atm. signal for C losses in Non-CO 2 gaseous compounds C: correcting atm. Signal for CO 2 release bypassing the ecosystem stocks (internat. trade) D: correcting land-based signal for C accumulation in wood products pool

7 Janssens et al., 2003, Science 300(5625): Europe, Ecosystem C Balance Ecosystem Area (Mha) NBP (Tg C/a) High estimate Forest, wooded land 389 (27) 377 (159) sink Croplands 326 (32) -300 (186) source Grasslands 151 (36) 101 (133) sink? Subtotal -199 (229) source? Undisturbed peatland 39 (6) 13 (7) sink Drained peatlands 16 (4) -30 (15) source Peat extraction -50 (10) source Low estimate TOTAL 111 (279)

8 Carbon fluxes in SOC in Europe (tc ha -1 y -1 ) in the 1st commitment period a b c d e f Simulated carbon fluxes in soil organic matter in Europe (tc ha -1 y -1 ) in the commitment period (business-as-usual scenario); (a c) arable fields, (d f) grassland. Simulations were made using the mean soil organic carbon content reported by as the initial situation in 2000 (b and e), mean organic carbon content minus standard deviation (a and d), and mean organic carbon content plus standard deviation (c and f). Vleeshouwers & Verhagen, GCB 8: 519 (2002)

9 C loss under crops, C uptake under grass Country C flux (t C/ha/a) Reason Austria, crop Changes in crop rotation Belgium, crop Changes in management reduced intensity Finland, crop Peat oxidation, discounted over entire area UK, crop Grass to crop conversion, set-aside Germany, grass >0.2 Crop to grass conversion in 1960s

10 General Constraints SCALE Where is the economic optimum of C stocks in agricultural soils? NON-PERMANENCE C sequestration is immediately reversed to a source if sequestration measures cease (e.g. no-till)

11 European Specifics C sequestration potential in agricultural soils is highest in - highly degraded soils and - relatively dry-continental conditions Both situations are not typical for Europe European soils are less easily degradable than e.g., the great plain soils European climate is more humid than e.g. the great plains European soils and agricultural management have a high small-scale diversity, which complicates any generalisation (e.g. farm sizes in hilly regions < 50 ha land)

12 Potential measures for cropland Zero-tillage Reduced-tillage Set-aside Grasses and permanent crops Deep-rooting crops Animal manure Crop residues Sewage sludge Composting Improved rotations Fertilisation Irrigation Bioenergy crops Extensification Organic farming Depends on applied amount of organic matter per hectare. Larger scale: effect levels out. Trend: less manure t C/ha/y

13 Potential measures for grassland Increase the duration of grass leys t C/ha/y Change from short duration to permanent grasslands Increase of fertilizer on nutrient poor permanent grassland Intensification of organic soils with permanent grassland From Soussana, pers. comm.

14 Potential measures for peatlands Protection and restoration t C/ha/y Avoid row crops and tubers Avoid deep ploughing More shallow water table Convert arable to grassland Convert arable to woodland New crops on restored wetlands from arable New crops on restored wetlands from grassland Sheep grazing on undrained peatland Abandon for conservation

15 Potential measures for land conversion Convert arable to woodland t C/ha/y Convert arable to grassland Convert grassland to arable Convert permanent crops to arable

16 Factors limiting carbon sequestration Sink saturation Non-permanence Availability of land and resources Adoption of measures

17 Limitations by soil properties Suitability for spreading of sewage sludge Susceptibility to soil compaction ECCP, Working Group Sinks Related to Agricultural Soils, Final Report, 2002.

18 Availability of land and resources / potential Soil carbon sequestration (Mt CO 2 y -1 ) Measure Limiting factor Theoretical Technical Economic? all agric. Given feasible land used limitation by 2012 Cropland Zero-tillage Suitable land = 63 Mha Reduced-tillage Suitable land = 63 Mha < 103 <9? <0.9? Set-aside <10% of arable; < 7.3 Mha 103 Max = 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 ? Crop residues Surplus straw = 5.3 Mt dm y ? Sewage sludge Sewage sludge = 71 Mt dm y ? Composting Compost available at present = 160 t dm y -1 (8 M ha) ? Improved rotations 0 >0 0? Fertilisation Irrigation Bioenergy crops only current set-aside = 7.3 Mha Extensification current set-aside to extensify 30% of arable agr. = 20 Mha ? Organic farming Could increase to 10% = 7.3 Mha

19 Availability of land and resources / potential Soil carbon sequestration (Mt CO 2 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 Max Land conversion Arable to woodland current set-aside = 7.3 Mha Max Arable to grassland current set-aside = 7.3Mha Grassland to Land-use change since 1990 arable calculated as 2.7 Mha (since 1990)? Permanent crops Land-use change since 1990 to arable calculated as 0.4 Mha (since 1990)? Woodland to Negligible land-use change arable since 1990 =>

20 Availability of land and resources / potential Soil carbon sequestration (Mt CO 2 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 Possibly attractive on grass- land when new melioration is needed = 50 % of grass- 36 GHG: land area = 1.5 Mha More shallow water table

21 Environmental effects Tillage Amendments Conversion Peatland Herbizides, pestizides? Non-CO2 gases NH3, NOx?? Biodiversity? Water quality Soil quality Sustainable land management Productivity?

22 Best options 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 (crop rotation with ley farming) 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

23 Caveats Where are the soil / climate conditions with highest carbon sequestration potential? Soil carbon / land use maps! Present soil C stocks? What measures are best adjusted to regional management preferences? Regional land use / land management history Regional best practice Permanent, contiguous, long-term adoption of measures? Monitoring! Costs? Regional refinement of agroenvironmental measures necessary Research needed!

24 80 60 Present sources and nnual C sequestration potential in European agriculture Tg C-equivalents/yr N 2 O- Emission agriculture CH 4 - Emission agriculture Current C balance: mineral soils Current C source: cultivated peatlands Current Sink: no-till Potential C Potential C sink in sink in agriculture agriculture (by 2010) (theoretical) Freibauer, Eur. J. Agron. 19 (2003): 135, Smith et al., GCB 2000, Janssens et al. Science (2003)

25 European Policy 1) European Climate Change Programme (ECCP) Working Group on Sinks Related to Agricultural Soils Recommendations for Climate Policies Final report ) Environmental Technology Action Plan (ETAP) Issue Group Soil Recommendations for Environmental Policies In progress

26 Conclusion of ECCP, WG Soils Quantification of carbon sequestration potential is limited by strong regional differences in (1) the sequestration potential of the measure, (2) the environmental impact of a measure, and (3) the socio-economic impact of the measure. Decentralised strategy, which takes into account the national, regional and even site-specific variation in socio-economic and environmental factors! Soil carbon has important role for the vital functions of soil and contributes to the long-term maintenance of soil fertility and function. Carbon sequestration also as a contribution to a European policy of soil protection. Carbon sequestration in soils is likely to have only a limited potential for greenhouse gas mitigation in isolation. It needs to be part of a broader strategy of measures for greenhouse gas mitigation and would provide added value to efforts to (1) improve the sustainability of soils and agriculture through increased organic carbon levels in soils. (2) The greatest potential: substitution of fossil fuels with bio-energy crops, which has the double benefit of offsetting carbon emissions and additional carbon sequestration in soils.

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