Annette Freibauer. Johann Heinrich von Thuenen-Institute Institute for Agricultural Climate Research Braunschweig, Germany

Transcription

1 Annette Freibauer Johann Heinrich von Thuenen-Institute Institute for Agricultural Climate Research Braunschweig, Germany

2 Questions addressed 1. Where are the highest soil carbon stocks, and the highest soil carbon losses by land use? 2. How can natural soil carbon stabilization mechanisms help to support adaptation and mitigation of climate change? 3. How could future land-use systems on high-carbon soilslooklike? 2

3 Outline Situation now Carbon stocks and stabilization Carbon sources and sinks in European soils Hotspots of soil carbon losses by European land use Vision 2050 Multifunctional, resilient land use systems High-carbon, high-biodiversity zones Novel land uses and opportunities 3

4 Conditions favouring carbon stabilization in soil Mechanisms: Low microbial activity C input > C output Stabilization > Mobilization Conditions: High C input from litter Low-energy litter (decomposed) Cold temperatures Acidity Hydrological extremes: too dry, too wet High-activity clays Schulze & Freibauer

5 2008 Global organic carbon stocks Soil: 2000 billion tonnes of C (1 m) Vegetation: 470 billion tonnes o f C Global human CO 2 emissions: 9 billion tonnes of C / year (Canadell et al. PNAS 2007) A 3.5 change in soil carbon stocks equals all global human CO 2 emissions. A small change in C pools makes a big change for climate! The protection of soil carbon stocks also protects the climate. WBGU

6 Soils with high C stocks Steppe soil: Peat soil: Dry summers Deep- and intensively rooting grasses High C input from roots High earthworm activity Very wet Anaerobic subsoil Photos: Annette Freibauer6

7 2008 C stocks in European soils Soil C stocks in EU-27: 75 billion tons of C Of which: 50% in Scandinavia and UK 20% in peatlands (CLIMSOIL 2008) Organic carbon content (%) in the surface horizon of European soils (JRC, Jones et al. 2004, S.P.I.0472) 7

8 2008 Source million tons C per year Sink EU-25: Land carbon and greenhouse gas budget 41% 5% 16% 31% 3% 4% of area Forest Other wooded land Grassland Cropland Peat undisturbed Soil Biomass N 2 O CH 4 Peat drained CarboEurope-IP Final project synthesis, 2008; CLIMSOIL

9 2008 Hotspot: Land use change Conversion of grassland to cropland Photos: NABU, Germany 9

10 1990 Soil carbon loss after conversion of grassland to cropland Cumulative loss, relative to initial C stock, in % Total loss in topsoil: 5 to 40 t C per hectare Wet soils are more vulnerable than dry soils! C loss [%] German average, NIR 2006 German average, update Loess soil; Richter et al Sandy gley; Strebel et al Marsh soil; Burghard % H. Höper, 2009 Years after conversion 10

11 2007 Cropland: Erosion risks will increase Croplands are most vulnerable Row crops and hops increase risk. Water holding capacity lost by erosion: increased vulnerability to drought and further rain Cropping riparian areas makes soil loss risks uncontrollable. (e.g. Auerswald et al. 2009) Photos: D. Deumlich, ZALF 11

12 2006 Peatland use and greenhouse gas emissions CO 2 CH 4 N 2 O CO 2 CH 4 Aerated zone EU-25: 20% of soil C stocks in peat 7% peat area ~4% drained peat area (>60% of peat area) Montanarella et al. Mires & Peat 2006 Natural peatland Drained peatland Capillary fringe Watersaturated 12

13 2009 Peatland use and greenhouse gas emissions Germany: 4% of national GHG emissions from agricultural peatlands Cropland: 11 t C/ha/yr Grassland: 5 t C/ha/yr (vti, Gensior et al, NIR 2009) GHG reduction by peatland restoration: Fen: -8 t C/ha/yr Bog: -4 t C/ha/yr Costs: /t CO 2 (M. Drösler et al., unpublished project results) 13 Photos: Annette Freibauer

14 2030 Global CO 2 abatement costs Tillage & residues Difference across 6 German regions Organic soil restoration McKinsey

15 1970 Land use 1970 Regionalization and diversity: Small fields Small machinery Many landscape structural elements Many different crop types 15

16 2010 Land use 2010 Concentration and rationalization. More optimized for largescale technology More efficient in onedimensional, onedirectional sense Spatial segregation of animal and crop production Flexible reaction to subsidies and EU agricultural policy 16

17 2050 Vision 2050 Climate change has continued: extremes and surprises have increased: diversity, flexibility and resource protection are life insurances for economic viability of land use. Increasing pressures have risen land prices: unique focus on biomass production is not enough. EU subsidies are tied to environmental services and benchmarks for peatland water table, C stocks in soils Continued optimization to more dimensions, better integration between producers and consumers at various stages, value product cascades and local to regional matter cycling 17

18 2050 Towards continuous soil cover Croplands wastes photosynthetic potential = options for C sequestration can use periods of bare soil while radiation is high Improve mixtures for higher C returns to soil, and N fixation (leguminous undercrops, which are left in winter) 18

19 : Subsoil management for resilience to drought and C capture Stress prevention, not stress tolerance! Take up the chernozem system: Continuous cover High residue return to soil Deep-rooting crops (alfalfa, hemp, rapeseed ) Earth worms Crop breeding to enhance root intensity and root depth (NOT: grain yield) 19

20 2050 Conserve high vulnerable soil C stocks High-carbon, high biodiversity zones No cropping on soils in riparian areas Forest or grassland buffer strips along rivers and wetlands Peatland restoration and new peatland use for paludiculture Construction of new peatlands and wet soil areas for seasonal water storage in upper catchments 20

21 2050 Urban soils Soils with vegetation transpire, cool, reduce heat stress Urban soils an unexplored carbon store? 21

22 2050 Cascade use: avoiding land pressure Solving conflicting demands (food, energy ): cascade use from highest value to mass services (energy) Less waste 22

23 2050 Vision 2050 Land use produces primary products for multiple cascade uses Agro-Parc : Local to regional re-use cycles of CO 2 and nutrients High-carbon, high biodiversity zones Working with the strengths of nature to buffer nutrients, seasonal water shortage, extreme events Smart adapted land use systems Multi-crops with leguminous soil cover Riparian forests for timber, water management, nutrient recovery and carbon sequestration Restored peatlands with new biomass systems Urban soils 23

24 Soil C fluxes: Average EU cropland 2.6 ( 9%) ( 28%) ( 30%) ( 9%) 3.2 ( 20%) 0 t C per hectare per year -0.1 ( 95%) CarboEurope-IP Final project synthesis, ( 100%) 24

25 Global carbon stocks by ecosystem b) Vegetation Soil Mean WBGU Carbon stock [t C per hectare] Boreal forests Temperate forests Tropical forests Savannahs Steppes Cropland Swamps/Peatlands Tundra 1998