Carbon Sequestration in Grasslands:
Climate Change Mitigation Potential
Whendee L. SilverRudy Grah Chair of Sustainability and Professor of Ecosystem Ecology
Department of Environmental Science, Policy, and ManagementUniversity of California, Berkeley
True Cost Accounting in Food and FarmingDecember 6, 2013
1950 1960 1970 1980 1990 2000 2010Year
310
320
330
340
350
360
370
380
390
400
Atm
osph
eric
CO
2 (pp
m)
August 2013
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
Atmospheric CO2 concentrations are increasing
2020
We need to do something
20082010
20122014
20162018
20202022
20242026
20282030
20322034
20362038
20402042
20442046
20482050
350
360
370
380
390
400
410
420
430
Proj
ecte
d At
mos
pher
ic C
O2 (
ppm
v)
Year
440
450
Hypothetical emissions reduction scenario
Reducing emissions alone will not mitigate climate change
1950 1960 1970 1980 1990 2000 2010Year
310
320
330
340
350
360
370
380
390
400
Atm
osph
eric
CO
2 (pp
m)
August 2013
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
Atmospheric CO2 concentrations are increasing
2020
1950 1960 1970 1980 1990 2000 2010Year
310
320
330
340
350
360
370
380
390
400
Atm
osph
eric
CO
2 (pp
m)
August 2013
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
Atmospheric CO2 concentrations are increasing
2020
Can land management be part of the solution?
Atmosphere carbon760 Pg
Vegetation carbon610 Pg
Soil carbon2000 Pg
(or more)
Photosynthesis
Plant/tissue death
Microbe respiration
Grasses allocate a high proportion of their photosynthate belowground to roots greater soil carbon pools
Grasslands cover a significant portion of the Earth’s land surface
*30% of global land surface *Over half of the global land use *50% of the UK land area *50% of California land area
Managing soils for increased carbon content
has many co-benefits:
• Fertility• Water holding capacity
• Soil stability• Sustainability• Productivity
Converting waste to food
Food and agricultural waste Compost it…..
And create a carbon sink
Plant production (aka forage) has increased every year following a one time compost application
Abo
vegr
ound
Net
Pri
mar
y Pr
oduc
tion
(g
/ m2 )
control compost
1 2 3 40
250
500
750
1000
Year
2009 2010 2011 2012
Ryals and Silver 2013 Ecological Application, Ryals et al. in prep.
A one-time application of compost increased soil carbon
Pre-treatment 2009 2010 2011
Ryals et al 2014 Soil Biology and Biochemistry
GHG MitigationGHG Emissions
Compost Manure NitrogenFertilizer
-40
-30
-20
-10
0
10
20
30
Glo
bal w
arm
ing
pote
ntia
l (M
MT
CO
2e)
Net
Life cycle assessment suggests much higher climate change mitigation potential
Redrawn from DeLonge et al. 2013
Applied to 1 million hectare
0-10 10-30 30-50 50-100
Depth (cm)
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0S
oil C
arbo
n (M
g ha
-1) Amended (11)
Extensive (24)
A survey of 35 fields showed that organic amendments increased soil carbon by depth
Silver et al. in prep
Extensive Amended
Management
0
50
100
150S
oil C
arbo
n (M
g ha
-1 to
1 m
)
…and that amended fields had an average of 40 Mg more soil carbon per hectare
Silver et al. in prep
1 metric ton of carbon per hectare over 6 million hectares = 21 million metric tons (MMT) of CO2e
* 1 MMT = 1012 g
•Livestock ~ 15 MMT CO2e/y
•Commercial/residential ~ 42 MMT CO2e/y
•Electrical generation ~112 MMT CO2e/y
* 1 MMT = 1012 g
1 metric ton of carbon per hectare over 6 million hectares = 21 million metric tons (MMT) of CO2e
Conant and Paustian 2002
Improved grazing practices can sequester soil carbon
Carbon sequestration potential from improved grazing practices:
Scaled to 12 million hectares of rangelands
0.4 to 0.9 Mg C ha-1 y-1: 15-37 MMT CO2e y-1
1 Mg C ha-1 y-1: 42 MMT CO2e y-1
* 1 MMT = 1012 g Data sources: Eagle et al. 2011, Conant et al. 2001
Summary1. Agriculture can be part of the solution to climate
change (in a significant way!)
2. Soil carbon sequestration is possible and quantifiable in rangeland soils
3. Key questions and next steps: What are the best grazing practices work and why?
Testing in arid and semi-arid grasslands.
Marin Carbon Project
Nicasio Native Grass Ranch
Support provided by:United States Department of Agriculture
United States National Science FoundationThe 11th Hour Foundation
The Marin Community FoundationThe Rathmann Family Foundation
The Lia FoundationThe Kearney Foundation for Soil Science
University of California, Berkeley
The Silver Lab
Marcia DeLonge Justine Owen Becca Ryals
Potential compost production: 27 to 33 MMT y-1
Enough to reapply to 12 million ha of rangelands every 17-40 years
Availability of compost
1950 1960 1970 1980 1990 2000 2010310
320
330
340
350
360
370
380
390
400A
tmos
pher
ic C
O2 (
ppm
)
September 2012
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography .
2020
1950 1960 1970 1980 1990 2000 2010310
320
330
340
350
360
370
380
390
400A
tmos
pher
ic C
O2 (
ppm
)
September 2012
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography .
2020
Can land management be part of the solution?
Global warming can’t be explained by solar cycles
http://www.ncdc.noaa.gov/cmb-faq/globalwarming.html
One quarter of the rangeland area in California:
= 23 Tg of CO2e y-1 (without including compost C)
= 337 Tg of CO2e y-1 (with compost C additions)
Scalability
* 1 Tg (Teragram) = 1012 g
Arctic Sea Ice Shrinks To New Low
Source: NASA
There are several sources and sinks of greenhouse gases associated with soil amendment application to grasslands
+ -
DeLonge et al. in review
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