Whendee Silver

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

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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

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20482050

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Proj

ecte

d At

mos

pher

ic C

O2 (

ppm

v)

Year

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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

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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