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  • 1. Climate Change Mitigation: A Low-Hanging Fruit of Agroforestry P. K. R. NAIR Distinguished Professor University of Florida, Gainesville, FL, USACBSAF, Belém, PA, Brazil: 21 – 25 Nov 2011
  • 2. Objective and ScopeSeparate the chaff from the grain: Evaluate the current state of scientific knowledge on the role of AFS in climate- change mitigation (and adaptation) meditated through C sequestration Identify the management factors that influence C seq in land-use systems and the extent of their relevance to AFS
  • 3. Ecosystem Services of Agroforestry• Soil Productivity – Local• Water-Quality Enhancement – Landscape• Biodiversity Conservation – Regional• Climate Change Miti & Adapt: – Regional → (C Sequestration) Global
  • 4. SPECIAL SUBMISSIONS: AGROFORESTRY SYSTEMS AND ENVIRONMENTAL QUALITYJournal of Environmental Quality Volume 40 (3), May–June 2011, pages 784–866.
  • 5. Climate Change Global warming refers to increase in temperature of the earth’s near-surface • Increased by an average 0.6°C since 1970 • IPCC (Intergov. Panel on Climate Change) projects an average rise of 1.1 – 6.4°C during this century • Believed to be caused by the increase in atmospheric concentration of greenhouse gases (GHGs) GHGs include: • CO2 , carbon monoxide (CO), methane (CH4), nitrous oxide (N2O) • CO2 is the major GHG.
  • 6. Mitigation (of) & Adaptation (to) Climate ChangeMitigation Avoiding emissions and sequestering GHGs: [Technological change and substitution that reduce emissions]Adaptation Reducing the vulnerability of natural systems against actual or expected climate change effects
  • 7. Climate Change MitigationGoal: Reduce net emissions and enhance sink capacity1. Avoiding or Reducing the Emissions • Increasing input-use efficiency (Management interventions) • Decreasing losses (Soil and water conservation)2. Sequestering CO2 in Terrestrial Biosphere • Forest/woody biomass (Aboveground, belowground) • Soil C sequestration (Aggregation, physical protection, recalcitrant C)
  • 8. Climate Change AdaptationGoal: Develop strategies to reduce negative impacts1. Enhancing Soil Resilience • Increasing SOC pool • Restoring degraded lands2. Adopting efficient land-use systems/practices • Conservation agriculture • Agroforestry • INM, IPM, …3. Improving NPP • New and improved germplasm • GM crops, etc.
  • 9. Carbon SequestrationThe process of capture and secure storage of C from the atmosphereIt entails the transfer of atmospheric C, especially CO2, and its secure storage in long-lived pools.(UNFCCC = UN Framework Convention on Climate Change)
  • 10. C Sequestration in Land-Use Systems Aboveground (Vegetation) Belowground (Soils)• Soils play a major role even in the terrestrial C cycle.• The soil C pool, to 1 m depth, consists of:  Soil organic C (SOC) estimated at 1550 Pg  Soil inorganic C about 750 Pg (1 petagram = 1015 g = 1 billion ton)Total soil C pool (2300 Pg) is 3X the atmosph pool.
  • 11. Agroforestry and Carbon Sequestration The UNFCCC allows use of C seq. through afforestation and reforestation (A & R) as GHG offset activities. Agroforestry is recognized as an A & R activity. AFS have a higher potential to sequester C because of their perceived ability for greater capture and utilization of growth resources (light, nutrients, and water) than in single-species crop- or pasture systems.
  • 12. 21 3 Silvopasture Dehesa, Northern Spain Homegardens Florida, USA Kerala, India 2 1 4 3 46 5 6 Silvopasture Shaded cacao Parklands MG, Brazil Bahia, Brazil Ségou, Mali Univ. Florida, Cent for Subtropical Agroforestry: Carbon Sequestration Studies, 2005 -
  • 13. Locations of CSTAF (Univ of FL) Soil Carbon Sequestration Studies Sites Location Climate (m.a.p; mean Soil Agroforestry Systems Coordinates temp. range)Florida, USA Humid subtropical; 1330 Ultisols Silvopasture: slash pine (Pinus elliottii) o28°to 29° N; 81° to 83° mm; -3 to 28 C + bahiagrass (Paspalum notatum); 5–W 20 yrNorthern/ Central Humid Atlantic/ subhumid Alfisols Dehesa oak silvopasture (QuercusSpain Mediterranean; 1200/ 600 suber); >50 yr40 to 43o N; 6 to 7o W mm; 6-18°C/ 8-26°CKerala, India Humid tropical; Inceptisols Homegardens: Intensive multispecies mixtures of trees, shrubs, and herbs in10o32’ N; 76o14’E 2700 mm; 27 to 32oC small (< 0.5 ha) holdings; > 35 yrSégou, Mali Semiarid tropical; Alfisols Parklands: Intercropping under 500 to 700 mm; 29 to 36oC scattered trees, > 30 yr old; and live13o 20’ N; 6o 10’ W fences and fodder banks, ~ 9 yr.Bahia, Brazil Humid tropical; Reddish- Cacao (Theobroma cacao) under yellow thinned natural forest (cabruca) or14o 0’ S; 39o 2’ W 1500 mm; 25 to 32oC Oxisols planted shade trees; 30-yr old.Minas Gerais, Brazil Cerrado: Subhumid Oxisols Silvopasture: Eucalyptus spp. with tropical; 1350 mm; 22oC understory of Brachiaria spp (fodder17o 36’ S; 46o 42’ W grass) or rice (Oryza sativa).
  • 14. General Objectives Quantify SOC accumulation and sequestration in different types of agroforestry systems in a variety of ecological and geographical conditions. Determine C storage in different soil fractions up to at least 1 m depth. Quantify, wherever possible, C contribution by C3 and C4 plants (~ trees and herbaceous plants) using natural C isotopic differences between the two groups.
  • 15. Carbon Sequestration and Stable Aggregates Hierarchical organization of aggregates: Silt+clay – microaggregates – macroaggregates Macroaggregates Microaggregates Silt+clay aggregatesSize, µm 250 – 2000 53 – 250 < 53Mean residence 1-10 10 – 100 100-1000time (MRT) of CyearsC:N; Enzyme High Medium LowactivityBinding agents Fungal hyphae, Micr. polymers, Organomineral fine roots, plant/ root exudates, complexes microbial residues polyvalent cationsMgmnt effects High Medium Low Parton et al. (1987); Christensen (2001).
  • 16. 100 262.5 Agroforestry vs. 80 Agricultural System Near Tree vs. Far from Tree Agroforestry vs. Forest 60 40 ∆AF (%) 20 0 -20 -40 -60 -80 1 2 3 4 5 6 7 8 Land-use Types 0 − 50 cm 50 − 100 cm ∆AF (%) = [(AF-Non AF) / Non AF] *100 # Systems; age (# years since AF system installation) Location Soil Order 1 Pine + pasture vs. treeless pasture; 30 yr Florida, USA Ultisols 2 Pasture under birch trees vs. treeless pasture; Northern Spain Inceptisols 3 Home garden vs. rice paddy; >50 y Kerala, India Inceptisols 4 Under tree vs. away from trees (Dehesa); 80 y Northern Spain Alfisols 5 Under trees vs. away from trees; Parkland system; >50 y Ségou, Mali Alfisols 6 Homegardesn vs. forest: >50 y Kerala, India Inceptisols 7 Cacao under shade vs. forest; > 30 y Bahia, Brazil Oxisols 8 Brachiaria + Eucalyptus vs. Treeless forage stand; 30 y Minas Gerais, Brazil OxisolsChanges in soil C stock under different AF vs. non-AF systems (Nair et al., 2010).
  • 17. Summary of Results Tree-based systems, compared to treeless under similar conditions, store more C in deeper soil. High tree density → high SOC content, esp. in the upper 50 cm soil and <53 µm soil fraction. SOC stock under longer term AF systems with high tree-density (e.g., homegardens, shaded perennials) comparable to that of natural forests. In sparse tree-density AFS, soil stores more C near than away from the tree. C3 plants (trees) contribute to more C in the silt- + clay-sized (<53 µm) fractions than C4 plants in deeper soil profile. Traditional systems with large C stock seem to have limited potential for sequestering additional C.
  • 18. Some Recent PublicationsBook: Kumar BM, and Nair PKR 2011 C Seq in AF Systems. Springer, Netherlands
  • 19. Some Recent Publications …Journal Articles:Nair PKR. C seq studies in AF systems: A reality check Agroforest Syst (in press)Nair PKR. Introduction to Sp Collection of papers 2011 J Env Quality 40: 784–790Howlett D, Mosquera-Losada M-R, Nair P KR, Nair, VD. 2011 J Env Quality 40: 825–832Tonucci RG, Nair PKR, Nair VD, Garcia R 2011 J Env Qual 40: 825 – 832Nair PKR, Nair VD, Kumar BM, Showalter JM 2010. Adv Agron 108: 237–307.Haile SG, Nair VD, Nair PKR. 2010. Global Change Biology 16: 427–438.Gama-Rodrigues EF, Nair PKR, Nair VD, et al. 2010. Environ Manage 45: 274–283.Saha SK, Nair PKR, Nair VD, Kumar BM. 2010. Plant and Soil 328: 433–446.Nair PKR, Kumar BM, Nair VD. 2009. J. Soil Sci. Pl Nutrition 172: 10–23.Nair PKR, Nair VD, Kumar BM, Haile SG. 2009. Environ Sci Policy 12: 1099–1111.Saha SK, Nair PKR, Nair VD, Kumar, B. M. 2009. Agrofor Syst 76: 53–65.Haile SG, Nair PKR, Nair VD. 2008. J. Environ. Qual. 37: 1789–1797.Takimoto A, Nair PKR, Nair VD. 2008. Agri Ecosyst Env 125:159–166.Takimoto A, Nair PKR, Alavalapati JRR. 2008. Mitig Adapt Strategy 13: 745–761.Takimoto A, Nair VD, Nair PKR. 2008. Agrofor Syst 76: 11–25.
  • 20. Methodological Challenges• Ambiguous Concepts• Allometric Equations• Soil Sampling: Depth, Sampling Plan• Soil Analytical Issues• Fixed Effect Models: Pseudo-replication Repeated measures• Inadequate/Inaccurate Reporting: Soil BD, extrapolation of site specific values
  • 21. Estimates of Carbon Sequestration Potential of AF systemsAF System sub-group Distribution (major regions) Approx. Estimated C stock Potential CSP in new including potential area, mill range (kg ha-1 yr-1) area (kg ha-1 yr-1) ha Above Below Above Below (including ground ground ground ground potential)Alley cropping and other tree Humid and subhumid tropics 650 Up to 15 Very low 2–5 5 – 75intercropping systems to 150 Temperate (N. America, Europe) 50 Up to 10 Up to 200 2- 6 30 – 100Multistrata systems (Shaded Mostly tropical humid and 100 2 to 18 Up to 300 2 – 10 50 – 150perennials, homegardens) subhumid lands, predominantly lowlands, but up to 2000 m altitudeProtective systems (Windbreak, Arid and semiarid lands of the 300 2 to 10 Up to 100 1–8 10 – 30riparian buffer, shelterbelts, etc.) world, primarily sub-Saharan Africa, China and N. and S. America,Silvopasture Grazing systems: mostly semiarid 450 2 to 15 Up to 250 3 – 10 20 – 90 and sub humid lands in Africa, India, and the AmericasWoodlots (firewood, fodder, land Firweood and fodder-tree lots are 50 1 to 12 Up to 140 1–5 20 – 70reclamation, etc.) mostly in tropics; Land reclamation plantings in special problem areas. (Nair, 2012)
  • 22. Influence of Management Factors on Climate Change M & AMgt Factors Premises CriticismsTillage Aids in incorporation of plant Tillage only helps move the C(Reduced/ materials and gaseous down. Benefits of reducedMinimum exchange bet. soil and tillage based on surface-soilTillage) atmosphere. sampling may be misleading.Residue Mgt, More plant materials added Overall, a good practice.Nutrient Cycling to the soil means more C Extent of benefits depends on added to the soil litter quality and local factors.Plant diversity Continuous plant cover; Evidence on long term benefitand admixture niche-complementarity of biodiversity on soil C seq is hypothesis anedotal at present.Soil erosion Keeps soil in place; No adverse criticismcontrol enhances productivityManure/Fert. Promotes crop growth and All C additions to soil may notapplication soil-aggregate formation enhance microaggr. formation. (Nair, 2012)
  • 23. Possible Management Factors Related to Climate Change M & A under AFSAFS Sub-Groups Location/ Possible Mgt Ecological Factors regionAlley Cropping and Tree Humid tropics, RM (NC), PD/PSM,Intercropping Temperate EC, RTMultistrata (Shaded Humid and PD/PSM, RM (NC),Perennials, Homegardens, …) subhumid tropics ECProtective Systems Temperate, EC, NC, RM(Windbreak, Rip. Buffer, …) semiarid tropicsSilvopasture Semiarid tropics, PSM, RT, EC, NC(Grazing, Browsing, …) Temperate EC = Erosion control; NC = Nutrient cycling; PD = Plant diversity; PSM = Plant-species mixture RM = Residue management; RT = Reduced (minimum/zero) tillage (Nair, 2012)
  • 24. Strengths Opportunities High above ground biomass  Enhanced above-ground C storage production  Increased SOM content Deep root systems of trees  More stable C in deeper soil layers High litter-fall and ground cover  More ground cover and litter fall Efficient nutrient cycling facilitating better nutrient cycling More stable C in deeper soil layers and control of soil erosion  More plant diversity leading to Plant diversity and biodiversity “safety net” of nutrients and Species admixture reduced NPSP Control of wind and water erosion  Overall, better ecosystem Amelioration of non-point source sustainability pollutants  Increasing global interest in Biodiversity conservation environmental ethics Weaknesses (Internal) Threats (External) Lack of rigorous and long-term  Lack of adequate recognition of quantitative data on potential AFS and trees on farms in int’l benefits policy initiatives and mechanisms Site specific nature of systems such as REDD+ making large-scale extrapolation  Insufficient valuation methods for difficult assessing ecosystem service Paucity of standardized methods benefits and procedures for sampling and  Excessive importance to economic estimation of C seq in AFS over environmental benefits in Multiplicity of factors and complex adoption incentives nature of interactions  Inadequate institutional niche for Difficulty in estimating area under agroforestry at national and different AFS international levels Figure 1. A SWOT analysis of the role of agroforestry systems in climate change M & A. (Nair, 2012)
  • 25. Carbon Sequestration – Biodiversity Relationship Functional relationship between biodiversity and C seq. based on the “niche-complementarity” hypothesis: • a larger array of species in a system leads to a broader spectrum of resource utilization making the system more productive. Biodiversity cannot be expressed quantitatively unless its attributes can be expressed in quantitative terms. Evidence on whether the carry-over effect of higher biodiversity will translate into long-term C storage in soils is anecdotal at present.
  • 26. Concluding Remarks Climate-Change M & A is a “low-hanging fruit” of agroforestry. Given that AFS are estimated to be practiced in ~ 1.6 billion ha globally, the potential benefits are credible, but are seldom recognized. Lack of rigorous scientific data on the perceived benefits is the main reason for the lack of realization and even recognition of this potential. The way forward: Break away from rhetoric and focus on development of management practices based on integrated scientific data on biophysical and socioeconomic parameters.