Grassland management strategies to mitigate and adapt to climate change

Transcription

1 Grassland management strategies to mitigate and adapt to climate change Donal O'Brien Livestock Systems Department, Animal and Grassland, Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork

2 Introduction Grasslands are a key European ecosystem Cover 33% of agricultural area Over 65% in some countries e.g. Ireland and the UK Demand for food products from grassland is rising 1.4%-2% growth beef and dairy demand Food products from grassland are carbon intensive Increasing concerns over climate change Need to adapt and mitigate greenhouse gas (GHG)

3 State of grasslands Majority of world's grassland on poor quality soil Overgrazing common problem Soil Erosion Weed Encroachment Several drivers of overgrazing Population growth Urbanization Breakdown of transhumance system

4 Grassland and climate change Pastures are vast stores of Carbon Store 50% more carbon than global forests Can contribute to climate change mitigation via sequestration World's grassland can sequester up to 3 Gt of C/year Debatable how long grassland can sequester C IPCC consider grassland management key tool to reduce agricultural greenhouse gas (GHG) emissions Management also key to adapt to climate stress

5 Climate management strategies for grassland Optimize grazing intensity Mixed species grassland Improve productivity Nutrient management Restoring degraded lands

6 Optimize grazing intensity Under or over grazing adversely effect grassland C stocks Carbon loss from soil Reduced rates of soil C sequestration Correct stocking rate where imbalance occurs Grass budgeting Pasturebase - Online grazing tool Match grass supply and demand Remove excess forage and conserve Feed conserved forage during deficits Grass growth Herd Demand

7 Mixed swards Introducing new species with high productivity reduces emissions Improves soil organic C Reduce N fertilizer requirements and costs Deep rooted grasses with high productivity have greatest potential to increase soil organic C stocks Greatest impact of low productivity swards or savannahs Added benefit of improving resilience and biodiversity

8 Improve productivity Aim to increase food output from grassland for the same level of input Plant breeding - Higher producing grass cultivars Irrigation Fertilization rate Measurement is key to benchmark performance Farmer discussion groups Online tools - Farm profit monitor

9 Improve productivity Plant Breeding Wilkins and Humphreys, 2003

10 Effect of milk yield Gerber et al. 2011

11 Nutrient management Soil C sequestration positively correlated to mineral N Increase artificial N ferilizer use Introduce or increase sward legume content Intensively managed swards sequester over 2 t C/ha more than extensive systems But excess N fertilizer application increases N2O emissions Must match fertilizer application to plant growth

12 N 2 O Emissions (kg N ha -1 yr -1 ) Milk Production (t ha -1 yr -1 ) Nutrient management Use of legumes Clover can substantially reduce emissions Replaces mineral N Little or no N 2 O associated with biological N fixation Clover can fix up to 120 kg N ha Measured Simulated Milk production GG+FN GWC+FN GWC-FN G-B WC-B Li, Humphreys, Lanigan (2011) PloS-one

13 Restoring degraded lands Large areas of pasture land operating well below potential Improve productivity Increase soil organic C Key practices to restore degraded lands Reseeding or replanting of grasslands Improving soil fertility via manure application Retaining crop residues Conserving water and irrigation

14 Carbon footprint and grassland Key measure of food product is carbon footprint Greenhouse gas emissions/unit of food Measured using IPCC and life cycle assessment - ISO approved method Simulates on and off-farm sources and sinks of GHG from grassland farms Correct application of LCA uses appropriate unit and distributes footprint across farm products Fat and protein corrected milk and meat

15 IPCC (National GHG inventory) Dairy Farm Harvesting Cultivation Housing Grazing Soil Manure Milk Meat GHG NH 3 NO 3

16 Life Cycle Assessment Dairy Farm Off-farm Inputs Fertilizer Pesticides Feedstuff Livestock Fuel Electricity Machinery Etc.. Cultivation Soil Harvesting Grazing Housing Manure GHG NH 3 NO 3 Milk Meat GHG NH 3 NO 3

17 t CO 2 e/t milk solids Effect of GHG accounting method on grazing and confinement systems LCA Grass LCA Confine IPCC Grass IPCC Confine Other inputs Fertiliser Concentrate Indirect N loss Grazing returns Managed Manure Enteric fermentation O Brien et al.,2011 Accepted Mitigation objective? Reduce Global GHG emissions or maximise National compliance

18 Carbon footprint and grassland Typically global studies report grassland systems have above average C footprint But temperate grassland systems have the lowest C footprint e.g. New Zealand or Irish grazing systems Pan European studies show grassland to be most C footprint efficient for milk Include land use emissions Include soil organic sequestration But for meat comparisons are difficult - Large diversity of beef and sheep systems

19 High performance comparison Carbon footprint of milk from grazing systems amongst the lowest in the world Most global comparisons only consider regional or national average farms Goal - Compare carbon footprint of milk from high performance dairy systems Irish Grazing System (Horan et al., 2004, 2005) UK Confinement System (Garnsworthy et al. 2012) USA Confinement System (DairyMetrics)

20 Farm Information Item Irish UK USA Milk yield, kg/cow 6,262 10,892 12,506 Fat, % Protein, % Replacement rate, % Live weight, kg Concentrate, kg DM/cow 320 2,905 3,355 N fertilizer, kg N/ha

21 Carbon footprint of milk of high performance dairy systems +4% +6%

22 Carbon footprint and grassland Within nations or regions large variability in C footprint of similar grassland farming systems British dairy farms C footprint range kg of CO2/litre of milk Irish beef farms C footprint range from kg of CO2/kg of live weight Grassland management practices can be implemented to improve productivity and C footprint Nutrient management Extending the grazing season

23 Irish Carbon audits 124 dairy farms successfully audited But not representative of Rep. of Ireland West and North-West excluded Livestock inventory and milk production Electronic - DAFM, ICBF, Co-ops Annual on-farm survey Animal feeding plan Fertiliser use and manure management Fuel, Chemical, Water use etc

24 FPCM produced Histogram of Carbon Footprint of Milk of 124 Irish Dairy Farms 25% 20% 15% 10% 5% Mean: 1.11 SD: %: %: 1.38 Skew: % kg CO 2 -eq/kg fat and protein corrected milk (FPCM)

25 Grazing management and C footprint of Irish dairy farms kg CO 2 -eq/kg FPCM Kg CO 2 -eq/kg FPCM % 20% 40% 60% Farm N efficiency Grazing days

26 Relationships between Farm Measures and Carbon Footprint of Milk No single farm measure explained variation between farms carbon footprints of milk Stepwise multiple regression - Carbon footprint of milk best explained by: Farm N efficiency, milk yield/cow, grazing season and replacement rate (R 2 = 0.75) Mitigation is possible by management changes Improving total genetic merit via EBI Legumes White clover

27 National abatement potential National potential assessed via MACC Dairy and Agricultural Sector Menu of Irish mitigation measures National research only Measures ranked by their individual costs IPCC and LCA approaches applied Baseline assumes 50% increase in milk output by 2020 relative to (Food Harvest 2020)

28 Marginal abatement cost curve

29 Conclusions Grassland climate management strategies are available and economically viable Postulated Barriers to implementation Social - Insecurity of tenure Technical - Climate change and GHG emissions Economic Rising costs of fertilizers Need to quantify and capture the effective potential of management

30 Thank you for your attention