Soil Carbon Sequestra0on and Climate Change

Transcription

1 Soil Carbon Sequestra0on and Climate Change Rattan Lal Ohio State University Columbus, OH USA

2 SOME ANOMALIES AND CONTRADICTIONS PARAMETER SOIL SCIENTISTS GEOMORPHOLOGISTS/ SEDIMENTOLOGISTS 1. Can soils make a difference? Yes No, small if any 2. Is soil erosion a source or sink? Source Sink 3. Can agriculture be a solution? Of course, it must be No, may not make much difference

3 ANTHROPOGENIC EMISSIONS (Pg) BY CARBON CIVILIZATION I. Land use (i) Prehistoric : 320 (ii) : 136 (iii) : 30 II. Fossil Fuel combustion (i) : 200 (ii) : 190 These emissions have and will affect the ecosystems from which we derive food, feed, fiber, fuel and shelter. 3

4 SHORT VS. LONG-TERM CYCLE Short-Term : Exchange of C between atmosphere, biosphere, soil and the ocean, years (decadel scale) Long-Term : Geochemical cycles which affect C exchange between rocks and the surficial reservoirs, years (multimillion years scale)

5 CARBON POOLS IN DIFFERENT RESERVOIRS FOR THE LONG-TERM CYCLE Reservoir C Pool (10 18 g) Carbonate in Rocks 60,000 Organic C in Rocks 15,000 Ocean (HCO 3-, CO 3-2 ) 42 Soils 4 Atmosphere 0.8 Biosphere 0.6 There is extremely little CO 2 in the atmosphere compared to that in the rocks. Thus, if inputs and outputs are not closely balanced, the atmosphere would become overwhelmed with CO 2.

6 PROCESSES OF LONG-TERM C CYCLE 1. Uptake of atmospheric CO 2 by weathering of Ca and Mg silicates. 2. Weathering of ancient organic matter on the continent and burial of new OM in marine sediments. 3. The thermal breakdown at depth of carbonate minerals and OM via metamorphism, magmatism and diagenesis. Fossil fuel combustion by humans is a special case of greatly accelerated OM weathering.

7 THE LONG-TERM CARBON CYCLE (10 18 G) BERNER (2009) Volcanism, Metamorphism, Diagenesis Burial Weathering CARBONATES (60,000) OCEAN (42) SOILS (4) ATMOSPHERE (0.8) BIOTA (0.6) Weathering ROCK ORGANICS (15,000) Burial Volcanism, Metamorphism Diagenesis

8 WEATHERING OF SILICATES CO 2 + CaSiO 3 CaCO 3 + SiO 2 CO 2 + MgSiO 3 MgCO 3 + SiO 2 -Urey Reactions

9 CARBON POOLS IN DIFFERENT RESERVOIRS FOR THE SHORT-TERM CYCLE Reservoir Pool (10 15 g) Ocean 42,000 Fossil Fuel 5,000 Soils (2-m) 4,000 Atmosphere 780 Biota 620

10 THE TERRESTRIAL AND OCEANIC PROCESSES IMPACTING ATMOSPHERIC CHEMISTRY Atmosphere 800 Pg (400 ppmv) Pg/yr (2.2 ppm/yr) Land Fossil Fuel Ocean 10

11 GLOBAL CARBON BUDGET SOURCES FF combustion and cement production (10 PgC/yr) + Land Use Conversion (1.6 PgC/yr) + Erosion (1.1 PgC/yr) + Ocean Precipitation (0.77 PgC/yr) 11

12 GLOBAL CARBON BUDGET SINK Ocean Uptake (2.3 PgC/yr) + Atmosphere Uptake (4.3 PgC/yr) + Weathering (0.22 PgC/yr) + NBP (0.75 PgC/yr) + Unknown Land Sink (3.8 PgC/yr) 12

13 KNOWN UNKNOWNS IN GLOBAL C BUDGET Source: Erosion-Induced C Emission Sinks: Soil uptake, forest uptake 13

14 Burial of Biomass Burying trees in a landfill Biochar burial Karlen, Lal et al., Crop residues: The rest of the story. Env. Sci. & Tech. 43: Oceanic burial Crop residues Trees Legislation restriction 14

15 TROPICAL DEFORESTATION Decade Deforestation (10 6 ha/yr) C Emission (TgC/yr) C removal by Regrowth (TgC/yr) Average Range Average Range Average Range 1990s s

16 DECLINING EFFICIENCY OF NATURAL SINKS The efficiency of natural sinks has decreased by 5% over the last 50 years, and will continue to do so in the future. 16

17 GRAIN YIELD AND GLOBAL WARMING Each ( C) degree of global warming could potentially cut grain yield by 10%, with devastating effects on food security. Nabhan (2013) 17

18 URBAN AGRICULTURE It is more than just about growing food in urban lands, but also the nurturing of friendship and community spirit of solidarity among neighbors by sharing the produce, and fostering the culture of restoring drastically disturbed soils around the homesteads of urbanites. 18

19 CLIMATE-RESILIENT AGRICULTURE If thought of global warming creeps into your mind while restoring degraded soils by establishing a cover crop, applying mulch, using compost or planting trees; don t stop nurturing the soil but instead do so with even a greater enthusiasm and urgency. To reduce to size of the over-grown footprint of the C-civilization, we need more than just the science. We also need the political willpower to restore eroded, salinized, compacted, and depleted soils and strengthen their ecosystem functions and services. 19

20 Mitigating Climate Change Carbon Management and Geo- Engineering Reducing Emission Carbonation Sequestering Emission Improve Efficiency Abiotic Biotic Low C-Fuel No C-Fuel Oceanic Geologic Terrestrial C-Neutral Fuel Oceanic 20

21 MIMICKING THE LONG-TERM C CYCLE (SHORT-CUT) Will reactions which occur over hundreds of millions of years over the geologic time scale be effective over human time scales of decades? 1. Geologic sequestration EOR, CBM, Saline Aquifers 2. Oceanic sequestration 3. Carbonation

22 POTENTIAL MITIGATION STRATEGIES INVOLVING THE TERRESTRIAL BIOSPHERE Terrestrial Biosphere Soil Biota Atmosphere Fossil Fuel Ocean 22

23 BIOSEQUESTRATION OF ATMOSPHERIC CO 2 Only 0.05% of the 3800 zettajoules (10 21 J) of solar energy is absorbed annually as GPP Gross Primary Productivity (GPP) = 123 Gt C/yr Net Primary Productivity (NPP) = 63 Gt C/yr Net Ecosystem Productivity (NEP) = 10 Gt C/yr Net Biome Productivity (NBP) = 3 Gt C/yr If we control what plants do with carbon, the fate of CO 2 in the atmosphere is in our hands -Freman Dyson (2008), BioScience (10/10) 23

24 VULNERABLE CARBON POOLS HIMALAYAS TROPIC REGION 24

25 GLOBAL SOIL EROSION & DYNAMICS OF SOIL ORGANIC CARBON 1500 x C In world soil 5.7 x g/ y r C Displaced due to erosion 1.1 x g/ y r decomposition and emission to the atmosphere 3.99 x g/ y r Stored within the terrestrial ecosystem 0.57 x g/ y r Transported to the ocean 25

26 SOIL C SEQUESTRATION Innovative Technology II Relative Soil C Pool Subsistence farming, none or low off-farm input soil degradation New equilibrium C Sink Capacity Rate ΔX Adoption of RMPs ΔY Maximum Potential Attainable Potential Δt Accelerated erosion Innovative Technology I NT INM & NUE Cover Crops Biochar Agroforestry Desert. Control Afforestation Pasture Mgmt H 2 O harv., DSI 20 MRT = Pool Flux 0 Lal, Time (Yrs) 26

27 NO PANACEA NOR A SILVER BULLET Carbon Management and CA T R Sustainable Intensification S Nutrition- Sensitive Agriculture Agroforestry A D E O F F The Nexus Approach Micro- Irrigation GMOs INM Disease/ Suppressive Soils Precision Farming Farming System Analysis 27

28 SOIL TILLAGE GUIDE TEXTURE VS. MOISTURE REGIME Carbon Management and Clay Clay loam Surface drainage (Ridge/furrow system) Dry farming Water harvesting Soil Texture Silty clay loam Silt loam Sandy loam Minimum tillage (Disc plowing) Plowing at the end of rain (Rough seedbed) Water erosion Water erosion- crusting Water logging- water erosion Loamy sand No-tillage (Periodic fallowing) No-tillage (Periodic fallowing and Chiseling) Sand Perhumid Humid Subhumid Semi-arid Arid Water and wind erosion Wind erosion drought stress Moisture Regime Lal

29 Sequestration Sand or Silt Center particles CARBON SEQUESTRATION IN STABLE MICROAGGREGATES (WILLIAMS et al., 1967) Soil Aggregates Microaggregates Domain of clay crystals forming part of microaggregates A hypothetical model of a soil aggregate, illustrating the clustering of clay crystals to form domains, of domains to form microaggregates, and of microaggregates to form aggregates. Molecules of soil organic matter acts as bonding agents between domains and microaggregates, and sand and silt particles (after Williams et al., 1967) 29

30 NUTRIENTS REQUIRED TO CONVERT BIOMASS INTO HUMUS Crop Residues Humus Biochemical Transformations + (N, P, S etc.) Elemental Ratio Cereal Residues Humus C:N C:P C:S Straw photo: Humus photo:

31 TRADING NUTRIENTS FOR CARBON Sequestration of 10,000 kg of biomass C as humus requires additional nutrients: 833 kg N 200 kg P 143 kg S 28,000 kg of C in residues 62,000 kg of residues (oven dry) These ingredients will produce + 17,241 kgof humus Recalculated from Himes, 1998.

32 WORLD SOILS HAVE NOT BEEN A MAJOR SINK IN THE PAST 1. Measurements are lacking 2. Soils have been used exploitatively/extractively 3. Soil management has been such as to make them source Drainage Plowing Residue removal 32

33 SCIENTIFIC CHALLENGES IN-SHORT-TERM CARBON CYCLE 1. Understand the biogeochemical mechanisms determining the carbon exchanges between the land, oceans and atmosphere, 2. How these exchanges respond to climate change through climate-ecosystem feedbacks, which may accentuate or dampen both regional and global climate change, and 3. What are possible interventions to manage these feedbacks. 33

34 ROLE OF TERRESTRIAL ECOSYSTEMS IN THE SHORT-TERM CARBON CYCLE 1. By being a source or sink of atmospheric gases via (i) Natural and anthropogenic disturbances (ii) N enrichment by converting N 2 into reactive N (iii) S deposition 2. Climate change and soil carbon (i) Release of CO 2 by warming induced decomposition, (ii) Increase in erosion 34

35 CAPACITY OF SOIL CARBON SINK Total SOC pool to 2-m depth = 2400 Pg Increasing SOC pool by 1% = 24 Pg 1 Pg = 0.47 ppm C sink capacity for every 1% increment 11 ppm 35

36 WHERE MANAGEMENT IS POSSIBLE 1. Degraded Soils (i) Eroded (ii) Salinized (iii) Chemically degraded (iv) Physically degraded 2. Mined lands 3. Drained peatlands Managed Ecosystems 1. Croplands 2. Plantations 3. Grasslands 36

37 TOWARDS C-NEUTRAL AGRICULTURE INM No-till Farming Chatting with plants through molecularbased signals N, P, K, Zn, H 2 O Soil biota and ecosystems services 37

38 WORLD POPULATION (BILLIONS) RELATIVE FOOD PRODUCTION (Mg/ha) TECHNOLOGICAL INNOVATIONS Hand Tools Animal Power Rotations GREEN REVOLUTION Machine power Fertilizers Germplasm Improved cultivars Biotechnology No-till farming INM IPM Carbon sequestration Conservation agriculture Micro-irrigation Precision farming Perennial culture Complex rotations GMOs Sustainable intensification (SI) Rhizospheric processes Diseasesuppressive soils Soil-less agriculture Sky farming Urban agriculture Sky farming Recarbonization of the biosphere Nutritionsensitive agriculture SI Soil-less agriculture Sky farming Urban agriculture Restorative agriculture YEAR

39 SOIL ORGANIC MATTER AND CLIMATE CHANGE Will Climate Change: 1. Amplify SOM depletion 2. Exacerbate soil erosion 3. Alter global C cycle more drastically 4. Affect NPP through CO 2 fertilization effect Will Soil Processes: 1. Have mitigative impact 2. Adversely impact agronomic yield 3. Increase the land-based C sink 4. Decrease SOC pool through C-input in soil at high temperatures

40 CAN SOIL C SEQUESTRATION MITIGATE CLIMATE CHANGE? No, C sink capacity of soils of agroecosystems is finite (~1 PgC/yr for years). But, it has numerous co-benefits and is the more cost-effective option. Restoring soil quality, of which SOC pool is the important determinant, is essential to human wellbeing and nature conservancy.

41 SOIL STEWARDSHIP Soil stewardship and care must be embedded in every fruit and vegetable eaten, in each grain ground into the bread consumed, in every cup of water used, in every breath of air inhaled, and in every scenic landscape cherished. 41

42 Carbon Management and SOIL: THE GLOBAL ICON LAL, HANDOUT / Reuters Water Carbon Nitrogen Phosphorous Sulfur 42 en.wikipedia.org