Increasing the storage of carbon in the soil has been a controversial strategy for addressing climate change mitigation. What is the potential and why is there debate about this? How can we push beyond the debate to constructive action? Lini Wollenberg, a Gund Fellow, is an anthropologist and natural resource management specialist concerned with rural livelihoods and the environment. She currently leads a research program on Low Emissions Agricultural Development for the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS), based at the University of Vermont. Her work seeks to identify options for reducing the impacts of agricultural development and land use on the climate, while also improving livelihoods for the poor in developing countries. This presentation was given by Lini Wollenberg, CCAFS, on September 11, 2020 as part of the GundxChange Series.

1. Gund Exchange Sept 11, 2020
Soil carbon: A silver bullet for
climate change mitigation?
Finding a middle way

2. Modeled SOC change in top 2 meters of the soil. Histogram is of SOC loss (Mg C/ha), positive values
indicate loss. Sanderman et al. 2017 PNAS. Total loss 133 Gt C (488 Gt CO2e)
25-70% of agricultural soil carbon stock
has been lost in the last 12,000 years

3. More than half of agricultural
land is moderately or severely
affected by soil degradation

4. 1,500 Gt of soil organic carbon (C) in upper
100 cm
Soil carbon stocksAdapted from slide from Aldyen Donelly
Global SOC stock includes 550 Gt in peatlands

6. The Carbon clock is ticking
2 °C and 1.5 °C pathways
require negative
emissions
Mercator Institute
Roe et al. 2017
https://www.mcc-
berlin.net/fileadmin/data/clock/carbon_clock.htm 1.5°C

7. Global estimates of soil carbon potential in
agriculture
• Technical potential of 2 to
5 GtCO2/yr in agriculture
(Fuss et al. 2018)
• ~1.2 GtCO2e/yr
economic potential at
USD 10/tCO2e (Bossio et
al. 2020)
• SOC sequestration rates
and areas vary
• Uncertainties due to land
area, depth, and soil,
subsoil and landscape
processes
Paustian et al. 2016

9. 10.1007/s13280-019-01165-2
2019

10. A Grand Challenge
Soil carbon sequestration for climate change mitigation
• An opportunity that should be “neither dismissed nor exaggerated.”
(Bossio et al. 2020)
• A live debate that is pushing our knowledge forward (Rumpel et al.
2019)
….So how to move forward?

11. Time to move from
discussion of
potentials toward
doing…

12. The issues
No guarantee that what you
add will stay
• Agriculture is a driver of
soil carbon loss
• Need constant OM inputs
• Slow gains, quick losses
• Stability of storage:
Permanence and
saturation
You can’t easily tell how
much has been stored
• High variability over space
and depth at farm and
project scales
• Activity-based indicators
and data are poor
• 3-5 years to see change
Large-scale, sustained change is tough
(1) biophysical limits (water, nutrients, energy, exogenous inputs,
GHG trade-offs), (2) socio-economic barriers (C price, need for
ongoing incentives, slow policy change, investment risk, land tenure
etc), (3) context-specific solutions

13. Current public policy and private investment initiatives
are small scale, but offer entry points
• NDCs: At least 27 UNFCCC parties’ Nationally Determined
contributions refer to soil carbon and 11 have targets – more can be
done to specify targets
• Government initiatives: Australia’s Carbon Farming Initiative (50
registered farmers) and California’s Healthy Soils Program provide C
market incentives and subsidies to farmers
• Private sector initiatives Indigo’s Terraton Initiative: 1 trillion tons, 5
billion ha $12-24/ha, aim for quantification methods, technologies, and
innovative finance. Corporates: Danone, Mars, Bayer, Coca Cola,
Fonterra, Diageo and Olam. Entrepreneurs: KOFAR
• C-Market projects: Kenya Agricultural Carbon Project (World Bank
Biocarbon Fund): 37,000 smallholders, 1 MtCO2e verified mitigation
from trees and soil in East Africa, since 2009. VERRA indicates ~12
projects developed or in pipeline.

14. Adapted from slide by D. Bossio
Croplands - green
Grazing lands - blue
Intensity of color indicates higher
SOC potential
Soil carbon potential over next 20 years
in crop and grazing lands (IPCC)
SOC specified in NDC

15. Address barriers to implementation
Stakeholders consultation. Farmers (world, ≈ 1500)
https://www.circasa-project.eu
Slide courtesy of Claire Chenu

16. Adoption of a practice that
stores/preserves carbon
Market based on adoption
of sequestering practices
or management options
“New” market approachs are ready
©V.Chaplot–RainfedRiceLaoPDR
http://calclimateag.org/hsp/
Slide courtesy of M. Bernoux

17. • World Bank’s Agriculture investment portfolio for adaptation or mitigation has
nearly doubled since 2016/17 from 28% to 56%
• Plan to increase share of projects with Climate Smart Agriculture ‘triple wins’ to 66% by 2025
• Reaching at least 20 countries and 10 million farmers
• Soil health enhancing practices will form a portion of these investments.
World Bank Commitments to Action on Climate Change
and Soils in Agriculture
Slide adapted from M. van
Nieuwkoop

18. Kenya Agricultural Carbon Project (KACP)
• The first soil carbon project earning carbon credits
• Pilot project helped 60,000 farmers on 45,000 hectares (ha) to adopt
sustainable agricultural land management practices leading to carbon
sequestration.
• First credits earned in 2016 - 10,790 VCUs since then
World Bank Investment examples
Purpose:
• increase agricultural productivity and enhance resilience to climate
change risks in smallholder farming and pastoral communities
How:
• Up-scaling climate smart agricultural practice (including improving soil
investments, promoting crop diversification, and agro-forestry) and
strengthening the enabling environments.
Impact:
• Project will benefit about 522,000 households of smallholder farmers,
agro-pastoralists, and pastoralists directly, 340,000 households benefiting
from the county-level and public-private partnership investments and
over 600 micro-small-and-medium enterprises
Kenya Climate-smart Agriculture Project (KCSAP) ($250m)
Slide from M.
Nieukoop

19. Verra’s work on SOC Accounting
23 September 2020
• Expert Ag Land
Management Working
Group (ALM WG)
• New accounting
methodologies
• Incorporate technology
advances
• Adapt VCS rules
Photo source Sentinel-hub
Slide courtesy of Stefan Jirka, VERRA

20. 5Confidential © 2020 Indigo
Growers enroll in
Indigo’s carbon
offset program
Indigo establishes
baseline
1
Indigo supports farmer
in transitioning to
regenerative practices
Indigo gathers
data manually
and automatically
Indigo algorithm processes
data to quantify GHG
abatement and soil carbon
sequestration
Offsets are
verified and
validated
Value of offset
is transferred
to grower
Indigo sells offsets
3 5 6 7 842
.
Indigo Carbon is developing an end-to-end carbon offering for
growers to be paid for carbon abatement and sequestration

21. 9Confidential © 2020 Indigo
The Terraton Experiment is producing a comprehensive soil and
grower dataset on each sampled field
Protocol Data Produced
SOIL CARBON Soil Organic C (SOC) and Total C
BULK DENSITY Bulk Density
SOIL CARBON
to 1 METER
SOC and Total C, Texture, Total N, pH, CEC,
Macronutrients, Micronutrients, Bulk Density
SOIL HEALTH
pH, Nutrients, OM, Soil Respiration,
Wet Aggregate Stability
GROWER
INTERVIEWS
Agronomic Management History,
Production, Profitability, Qualitative Insights
SOIL MICROBIAL
COMMUNITY
Community sequencing to identify microbes,
arthropods, and other fauna
Areas sampled to date Planned 2020
Terraton Experiment Soil Sampling Operations: 3,330+
unique soil samples at shallow and deep depths have
been collected in 2019-2020
We are working with university and institutional research collaborators to analyze and publish our results

22. FAO RECSOIL program
Agreements with farmers or farmer associations to implement RECSOIL and
gain access to technical support and financial incentives).
GSOC map
GSOCseq map
GSOC-MRV Protocol
Manual of good practices
VGSSM + SSM Protocol
Global SOC Monitoring System
SOPs for soil organic carbon
Slide courtesy of R. Vargas, FAO

23. KOFAR products
• Rotuba
• Locally-produced organic fertilizer, commonly
sold in 50kg bags
• Inputs are sourced from agricultural residues
• Increases soil organic matter, which supports
root formation and water retention
• Nano
• Enzyme formula developed in the United
States
• Includes organic plant growth regulators,
nucleic acids, glycosides, & others
• Stimulates microbial life in soil; spurs growth
of beneficial fungi
23
Nano-supported roots on the
left; synthetic fertilizer-
supported roots on the rightAdapted slide of D. Gromko

24. Global agenda for collective action on soil
Foster vision and
awareness for
action, led by
champion actors
Demonstrate
investment case
through pilot funding
of commercially
viable soil carbon
initiatives
Identify and support
farmer incentives
Vermeulen et al. 2019

25. Getting the balance right
Source Campbell et al. 2019
• Set standards for optimal outcomes
• Monitor for negative impacts or create safeguards/no
go zones

26. Conclusions
We have a grand challenge, but we can work on it!
Action is needed on multiple fronts; it not just a technical implementation
problem.
• Set ambitious targets and work toward for large-scale, systemic change
across the public and private sector institutions, esp. incentives,
advisory services, novel technical options, political will. This will take
time.
• Test priorities and strategies with iterative, adaptive approaches that
consider optimizing impacts and trade-offs.
• Improve understanding of mitigation potentials and implementation
successes with monitoring of networks of long-term sites on farmers’
fields

27. Lini.Wollenberg@uvm.edu
Thank you!

28. Confidence higher (and uncertainly lower) for more aggregate
estimates (sub-regional, regional)
• Legacy of long-term experiments with
research-grade measurements over
decadal+ time scales
• Empirical data and meta-analysis provide
good estimates of regional-national
averaged responses
• Generally good understanding of principles
and drivers– predictive modeling
capabilities
 Comet Farm and Carbon Benefits
Project tools

29. Priority actions to meet climate targets
 Stop carbon loss
− Protect peatlands –32%-46% of all soil carbon (~500–700 Gt C), e.g. through
supply chain accountability and monitoring and enforcement of land use
boundaries
 Promote significant carbon uptake
− Identify geographic priorities, regional strategies and country champions
− Create platforms for sharing knowledge and practices among farmers, locally,
regionally and globally.
− Support public-private investment (technical de-risking, project match making)
and viable carbon-markets
− Demonstrate benefits that balance crop productivity, SOC and SDG impacts
 Set ambitious policy and standards
− Increase ambition and specificity for SOC targets in NDCs and other policy
− Integrate SOC sequestration into national best practice and green finance
standards
− Develop and harmonize low-cost monitoring systems

30. Relative contribution of additional carbon
sinks
Afforestation/
reforestation
29%
Agroforestry
1%
Wetland restoration
12%Forest mgmt
22%
Soil carbon
18%
Biochar
18%
Chart Title
A/R Agroforestry Wetland restoration Forest mgmt Soil C Biochar
9.9 – 26 GTCO2e

31. Systemic transformational change
Improved advisory services, novel technologies,
strong C-market, policy subsidies and regulation, company offsets,
impact investing, farmer learning and social movements (regenerative
agriculture, agroecology)

32. Not just about building soil carbon.
• Essential to avoid soil carbon loss
• 1,500 Gt of soil organic carbon (C) in upper 100 cm
Soil carbon stocksAdapted from slide from Aldyen Donelly

33. Local scale measurement
Accuracy in direct field measurements depend on:
• Variability in C stocks and stock change rates
(sampling intensity)
 Requires multiple 10’s of samples
• Magnitude of change rate (re-sampling
frequency)
 Requires resampling interval of 5 yrs +
• Accuracy of C stock determination at a point
(analytical methods)
 Spectroscopic analysis (MIR) can increase
throughput and reduce costs
 In situ (non-destructive) methods improving
but lower accuracy and other factors still limit
applicability
Conant & Paustian 2002
Adapted from slide
by K. Paustian
Direct measurement is too expensive
for routine use

34. Policy framework and initiatives
• NDCs: all sinks included, but total (C
seq and GHG reductions) is only 1/3
of what is needed (UNEP 2017)
• Many policy initiatives
 Forests: REDD+, Carbon Disclosure
Project and zero-
deforestation/deforestation-free supply
chain commitments
 Forest and land restoration: Bonn
Challenge
 Soil carbon: 4p1000, Bonn Challenge,
Global Soil Partnership, ITPS and
Healthy Soils Facility
 Peatlands: Ramsar Convention
Forest management 88
Deforestation 76
Reforestation 76
Bioenergy 64
Croplands 53
Grasslands 50
Afforestation 47
Agric. residues 40
Cookstoves 35
Rice 28
Degraded lands 27
Agroforestry 23
Peatlands 9
Soil C 8
Richards et al 2016
NDCs: Number of countries
planning mitigation

35. • Quantify the contribution of SOC
sequestration to mitigation targets
• Provide sectoral or sub-sectoral targets
in addition to economy-wide targets
Increase NDC ambition by: Increase transparency for global SOC
accounting
How can countries include SOC in future NDCs?
More ambition and tougher targets needed to achieve 1.5 - 2°C
Paris Agreement targets
Examples to include SOC in second 5-year NDC cycle:
Leverage support for national policies,
technical capacity, climate finance
• Specifying SOC in relation to SOC-supporting measures already
included in NDCs
• Setting conditional SOC mitigation targets for developing countries
NDCs as
indicator of
policy action
on soil health
and climate
Slide courtesy of L. Wiese-Rozanova

36. Specification of measures in the Nationally
Determined Contributions to the Paris Agreement
Measure/s
Countries specifying
SOC for this practice
Agroforestry/Silvo-pastoralism* Malawi, Palestine
Conservation agriculture Zambia
Grassland/ Pasture land management China, Japan, Uruguay
Organic amendments (manure, compost, biochar) Malawi
Reduced/stopped (crop residue) burning
Erosion control
Integrated soil fertility management
Reduced or no-tillage Uruguay
Residue retention (mulching) Malawi, Uruguay
Cover crops Uruguay
Fallow
Mitigation Adaptation
31 36
21 13
14 16
12 10
12 6
9 41
6 13
5 6
3 3
2 1
1 1
*Measures specified in relation to SOC
Weise-Rozanova et al, 2020

37. UNEP Gap report 2017

38. Source: World Bank Group,
State and Trends of Carbon
Pricing 2020, May 2020
Verra is a Global Leader in Offset Markets
Annual volume of issuances by crediting mechanism
Numberofprojects
VCS
23 September 2020

39. Fig. 4 | Regenerative soil carbon practice
consistent with promotion
of functional diversity to increase soil
carbon persistence. Soil
management designed to increase
persistence of soil organic carbon1
should be investigated for its alignment
with functional diversity. The listed
management recommendations also
increase organic carbon input (for
example, greater plant diversity45) or
persistence unrelated to functional
diversity (for example, avoiding periodic
drainage also reduces aeration in
addition to movement of carbon). Inset
colours relate to the three aspects
of functional diversity (molecular, spatial
and temporal) also used in Figs.
2 and 3. Interactions of effects over time
require specific attention in future
research (indicated by italics).

40. Soil Carbon
is 25%
of our natural
solution
40
Bossio et al. 2020, Nature Sustainability

41. But can also increase soil C by 8-88 Gt C
(over 20 years): e.g. reduced burning,
legume intercropping, agroforestry,
compost, manure, deep-rooted plants.
Issues: ambitious potentials, competition
for biomass, reversibility, MRV, prioritize

42. Cropland soil mitigation potential
Zomer et al. Nature
2017

43. Global soil carbon storage
potential
Slide courtesy of Aldyen Donnelly