1. Climate Change Mitigation:
A Low-Hanging Fruit of
Agroforestry
P. K. R. NAIR
Distinguished Professor
University of Florida, Gainesville, FL, USA
CBSAF, Belém, PA, Brazil: 21 – 25 Nov 2011

2. Objective and Scope
Separate 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
QUALITY
Journal 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 Change
Mitigation
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 Mitigation
Goal: Reduce net emissions and enhance sink capacity
1. 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 Adaptation
Goal: Develop strategies to reduce negative impacts
1. Enhancing Soil Resilience
• Increasing SOC pool
• Restoring degraded lands
2. Adopting efficient land-use systems/practices
• Conservation agriculture
• Agroforestry
• INM, IPM, …
3. Improving NPP
• New and improved germplasm
• GM crops, etc.

9. Carbon Sequestration
The process of capture and secure
storage of C from the atmosphere
It 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. 2
1 3
Silvopasture Dehesa,
Northern Spain Homegardens
Florida, USA
Kerala, India
2
1
4 3
4
6 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)
o
28°to 29° N; 81° to 83° mm; -3 to 28 C + bahiagrass (Paspalum notatum); 5–
W 20 yr
Northern/ Central Humid Atlantic/ subhumid Alfisols Dehesa oak silvopasture (Quercus
Spain Mediterranean; 1200/ 600 suber); >50 yr
40 to 43o N; 6 to 7o W mm; 6-18°C/ 8-26°C
Kerala, India Humid tropical; Inceptisols Homegardens: Intensive multispecies
mixtures of trees, shrubs, and herbs in
10o32’ N; 76o14’E 2700 mm; 27 to 32oC
small (< 0.5 ha) holdings; > 35 yr
Ségou, Mali Semiarid tropical; Alfisols Parklands: Intercropping under
500 to 700 mm; 29 to 36oC scattered trees, > 30 yr old; and live
13o 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) or
14o 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 (fodder
17o 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
aggregates
Size, µm 250 – 2000 53 – 250 < 53
Mean residence 1-10 10 – 100 100-1000
time (MRT) of C
years
C:N; Enzyme High Medium Low
activity
Binding agents Fungal hyphae, Micr. polymers, Organomineral
fine roots, plant/ root exudates, complexes
microbial residues polyvalent cations
Mgmnt 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 Oxisols
Changes 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 Publications
Book: 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: 784–790
Howlett D, Mosquera-Losada M-R, Nair P KR, Nair, VD. 2011 J Env Quality 40: 825–832
Tonucci RG, Nair PKR, Nair VD, Garcia R 2011 J Env Qual 40: 825 – 832
Nair 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 systems
AF 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 – 75
intercropping systems to 150
Temperate (N. America, Europe) 50 Up to 10 Up to 200 2- 6 30 – 100
Multistrata systems (Shaded Mostly tropical humid and 100 2 to 18 Up to 300 2 – 10 50 – 150
perennials, homegardens) subhumid lands, predominantly
lowlands, but up to 2000 m altitude
Protective systems (Windbreak, Arid and semiarid lands of the 300 2 to 10 Up to 100 1–8 10 – 30
riparian 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 Americas
Woodlots (firewood, fodder, land Firweood and fodder-tree lots are 50 1 to 12 Up to 140 1–5 20 – 70
reclamation, etc.) mostly in tropics; Land reclamation
plantings in special problem areas.
(Nair, 2012)

22. Influence of Management Factors
on Climate Change M & A
Mgt Factors Premises Criticisms
Tillage Aids in incorporation of plant Tillage only helps move the C
(Reduced/ materials and gaseous down. Benefits of reduced
Minimum exchange bet. soil and tillage based on surface-soil
Tillage) 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 benefit
and admixture niche-complementarity of biodiversity on soil C seq is
hypothesis anedotal at present.
Soil erosion Keeps soil in place; No adverse criticism
control enhances productivity
Manure/Fert. Promotes crop growth and All C additions to soil may not
application soil-aggregate formation enhance microaggr. formation.
(Nair, 2012)

23. Possible Management Factors Related to
Climate Change M & A under AFS
AFS Sub-Groups Location/ Possible Mgt
Ecological Factors
region
Alley Cropping and Tree Humid tropics, RM (NC), PD/PSM,
Intercropping Temperate EC, RT
Multistrata (Shaded Humid and PD/PSM, RM (NC),
Perennials, Homegardens, …) subhumid tropics EC
Protective Systems Temperate, EC, NC, RM
(Windbreak, Rip. Buffer, …) semiarid tropics
Silvopasture 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.