the effects of historical changes in global agricultural land on the terrestrial carbon cycle navin...
TRANSCRIPT
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The Effects of Historical Changes in Global Agricultural Land on the
Terrestrial Carbon Cycle
The Effects of Historical Changes in Global Agricultural Land on the
Terrestrial Carbon Cycle
Navin Ramankutty[[email protected]]Center for Sustainability and the Global Environment (SAGE)Institute for Environmental Studies, University of Wisconsin
Navin Ramankutty[[email protected]]Center for Sustainability and the Global Environment (SAGE)Institute for Environmental Studies, University of Wisconsin
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5.5 ± 0.5
Land Use
Atmospheric Pool 750
(stores 3.2 ± 0.2 yr–1)
Ocean 40,000
Units: Stocks - Gt-C Fluxes - Gt-C yr–1
NPP60
60
1.6 ± 1.0
Rh
92 90
Landplants 700
Soils 1550
The Global Carbon Cycle
Net =2.0 ± 0.8
(adapted from Schimel et al., 1995)
(status in the 1980s)
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Land Use EmissionsLand Use Emissions
• Current estimates -- Houghton et al.
• Land use data over 9 continental-scale regions
• “Book-keeping” model
• Current estimates -- Houghton et al.
• Land use data over 9 continental-scale regions
• “Book-keeping” model
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BackgroundBackground
0
1
2
3
4
5
6
7
1860 1880 1900 1920 1940 1960 1980
Carb
on E
mis
sions
(Gt-
C/y
r)
Fossil Fuel
Land Use(Houghton et al.)
0
1
2
3
4
5
6
7
1860 1880 1900 1920 1940 1960 1980
Carb
on E
mis
sions
(Gt-
C/y
r)
Fossil Fuel
Land Use(Houghton et al.)
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Houghton (1999)Houghton (1999)
Over the 1850-1990 period,
– Cropland change = 68% of total net C flux
– Harvest of wood = 16%
– Pastures = 13%
– Shifting cultivation = 4%
– Plantations = -1%
Over the 1850-1990 period,
– Cropland change = 68% of total net C flux
– Harvest of wood = 16%
– Pastures = 13%
– Shifting cultivation = 4%
– Plantations = -1%
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This StudyThis Study
• Geographically-explicit land use data, albeit restricted to croplands
• Using process-based ecosystem models
• Conducted as part of the Carbon Cycle Model Linkage Project (CCMLP), funded by the Electric Power Research Institute (EPRI)
• Geographically-explicit land use data, albeit restricted to croplands
• Using process-based ecosystem models
• Conducted as part of the Carbon Cycle Model Linkage Project (CCMLP), funded by the Electric Power Research Institute (EPRI)
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• Grand Slam Expt. -- concurrent effects of historical CO2, climate and land use on terrestrial carbon cycle
4 Terrestrial Biosphere Models HRBM -- Esser et al., Giessen, Germany IBIS -- Foley et al., Kucharik et al., Univ. of Wisconsin, USA LPJ -- Sitch, Prentice et al., PIK & MPI-Jena, Germany TEM -- McGuire et al., Tian et al., MBL, USA
3 simulations from 1860 to 1992(analysis from 1920)
• Grand Slam Expt. -- concurrent effects of historical CO2, climate and land use on terrestrial carbon cycle
4 Terrestrial Biosphere Models HRBM -- Esser et al., Giessen, Germany IBIS -- Foley et al., Kucharik et al., Univ. of Wisconsin, USA LPJ -- Sitch, Prentice et al., PIK & MPI-Jena, Germany TEM -- McGuire et al., Tian et al., MBL, USA
3 simulations from 1860 to 1992(analysis from 1920)
The CCMLP StudyThe CCMLP Study
S1: CO2 onlyS2: CO2 + ClimateS3: CO2 + Climate + Land use
S1: CO2 onlyS2: CO2 + ClimateS3: CO2 + Climate + Land use
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This TalkThis Talk
Effects of land use on the terrestrial carbon cycle
= Simulation S3 - S2
Effects of land use on the terrestrial carbon cycle
= Simulation S3 - S2
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Driving DataDriving Data
• CO2: Ice-core record + Avg. of Mauna Loa & South Pole
• Climate: Temperature and Precipitation anomalies from Jones et al. (1994) plus Leemans & Cramer (1991); surrogate for pre-1900
• CO2: Ice-core record + Avg. of Mauna Loa & South Pole
• Climate: Temperature and Precipitation anomalies from Jones et al. (1994) plus Leemans & Cramer (1991); surrogate for pre-1900
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Driving Data (continued)Driving Data (continued)
• Land Use: Boolean version of historical croplands data set of Ramankutty and Foley (1999)– Synthesis of the IGBP 1km global land cover
data set with historical cropland census data
• Land Use: Boolean version of historical croplands data set of Ramankutty and Foley (1999)– Synthesis of the IGBP 1km global land cover
data set with historical cropland census data
--> talk in parallel session B2, at 4:25 pm, Room EF --> talk in parallel session B2, at 4:25 pm, Room EF
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Global Cropland Distributions Source: Ramankutty & Foley, 1999Global Cropland Distributions Source: Ramankutty & Foley, 1999
Center for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, MadisonCenter for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, Madison
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Global Cropland Distributions Source: Ramankutty & Foley, 1999Global Cropland Distributions Source: Ramankutty & Foley, 1999
Center for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, MadisonCenter for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, Madison
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Global Cropland Distributions Source: Ramankutty & Foley, 1999Global Cropland Distributions Source: Ramankutty & Foley, 1999
Center for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, MadisonCenter for Sustainability and the Global Environment, Institute for Environmental StudiesUniversity of Wisconsin, Madison
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MicrobialRespiration
Net Primaryproductivity
NaturalVegetation
Biomass
Harvest
Product decayflux
ProductPools
= 1, 10, & 100 yrs
AgriculturalProducts
Net Carbon Exchange, NCE(positive into the atmosphere)
Net PrimaryProductivity
CropBiomass
Harvest
NaturalTurnover
Litter &Soil Organic Matter
Slash CropResidue
Product decayflux
= 1 yr
The Carbon Flow in CCMLP Expts.
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0
0,5
1
1,5
2
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
HRBM IBIS LPJ TEM
0
0,5
1
1,5
2
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
HRBM IBIS LPJ TEM
CCMLP Land Use FluxCCMLP Land Use Flux
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0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
CCMLPEnvelope
0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
CCMLPEnvelope
CCMLP Flux in Comparison with HoughtonCCMLP Flux in Comparison with Houghton
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0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
Houghton (cropland)
CCMLPEnvelope
0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
Houghton (cropland)
CCMLPEnvelope
CCMLP Flux in Comparison with HoughtonCCMLP Flux in Comparison with Houghton
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0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
Houghton (all landuse)
Houghton (cropland)
CCMLPEnvelope
0
0,5
1
1,5
2
2,5
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
Houghton (all landuse)
Houghton (cropland)
CCMLPEnvelope
CCMLP Flux in Comparison with HoughtonCCMLP Flux in Comparison with Houghton
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SummarySummary
CCMLP Houghton
1920-1990(Pg-C)
55-90 57
1980s avg.(Pg-C/ yr)
0.6-1.0 1.3
CCMLP Houghton
1920-1990(Pg-C)
55-90 57
1980s avg.(Pg-C/ yr)
0.6-1.0 1.3
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What does this imply?What does this imply?
In the 1980s,• Houghton (all landuse) = 2.0 Gt-C/yr• Houghton (croplands) = 1.3 Gt-C/yr
==> croplands = 65% of total land use flux
• CCMLP cropland flux = 0.6-1.0 Gt-C/yr– Scaled by 65%, ==> all landuse flux = 0.9-1.5 Gt-C/yr
In the 1980s,• Houghton (all landuse) = 2.0 Gt-C/yr• Houghton (croplands) = 1.3 Gt-C/yr
==> croplands = 65% of total land use flux
• CCMLP cropland flux = 0.6-1.0 Gt-C/yr– Scaled by 65%, ==> all landuse flux = 0.9-1.5 Gt-C/yr
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Implications for Missing SinkImplications for Missing Sinkbased on
C-budget Houghton(Gt-C/yr)
CCMLP(Gt-C/yr)
Atmospheric Increase -3.3
Fossil-Fuel 5.5
Land Use 2.0
Oceanic Uptake -2.0
Missing Sink -2.2
based onC-budget Houghton
(Gt-C/yr)CCMLP(Gt-C/yr)
Atmospheric Increase -3.3
Fossil-Fuel 5.5
Land Use 2.0
Oceanic Uptake -2.0
Missing Sink -2.2
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Implications for Missing SinkImplications for Missing Sinkbased on
C-budget Houghton(Gt-C/yr)
CCMLP(Gt-C/yr)
Atmospheric Increase -3.3 -3.3
Fossil-Fuel 5.5 5.5
Land Use 2.0 0.9-1.5
Oceanic Uptake -2.0 -2.0
Missing Sink -2.2 -1.1-1.7
based onC-budget Houghton
(Gt-C/yr)CCMLP(Gt-C/yr)
Atmospheric Increase -3.3 -3.3
Fossil-Fuel 5.5 5.5
Land Use 2.0 0.9-1.5
Oceanic Uptake -2.0 -2.0
Missing Sink -2.2 -1.1-1.7
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Why are the land use emissions different?
Why are the land use emissions different?
• Differences in the land use data?• Differences in the land use data?
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-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
1850 1870 1890 1910 1930 1950 1970
Rate of Change (Ramankutty)Rate of Change (Houghton)
Ra
te o
f C
ha
nge
of C
ropla
nd
(M
illio
n k
m2
/yr)
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
1850 1870 1890 1910 1930 1950 1970
Rate of Change (Ramankutty)Rate of Change (Houghton)
Ra
te o
f C
ha
nge
of C
ropla
nd
(M
illio
n k
m2
/yr)
Cropland Conversion RatesCropland Conversion Rates
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Why are the land use emissions different?
Why are the land use emissions different?
• Differences in the land use data?
• Differences in process representation?– regrowth, soil turnover, product fluxes, ...
• Differences in the land use data?
• Differences in process representation?– regrowth, soil turnover, product fluxes, ...
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0.04
0.06
0.08
0.1
0.12
0.14
0.16
200
400
600
800
1000
1200
1850 1870 1890 1910 1930 1950 1970
Rate of Change of CroplandCarbon Emissions
Rate
of
Change o
f C
ropla
nd (
Million k
m2/y
r)C
arb
on E
missio
ns (T
gC
)
0.04
0.06
0.08
0.1
0.12
0.14
0.16
200
400
600
800
1000
1200
1850 1870 1890 1910 1930 1950 1970
Rate of Change of CroplandCarbon Emissions
Rate
of
Change o
f C
ropla
nd (
Million k
m2/y
r)C
arb
on E
missio
ns (T
gC
)Houghton conversion rates and emissionsHoughton conversion rates and emissions
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CCMLP conversion rates and emissionsCCMLP conversion rates and emissions
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0
0.5
1
1.5
2
2.5
1920 1930 1940 1950 1960 1970 1980
Rate of Change of Cropland
Carbon Emissions CCMLP Envelope
Rate
of
Change o
f C
ropla
nd (
Million k
m2/y
r)C
arb
on E
missio
ns (T
gC
)
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0
0.5
1
1.5
2
2.5
1920 1930 1940 1950 1960 1970 1980
Rate of Change of Cropland
Carbon Emissions CCMLP Envelope
Rate
of
Change o
f C
ropla
nd (
Million k
m2/y
r)C
arb
on E
missio
ns (T
gC
)
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Why are the land use emissions different?
Why are the land use emissions different?
• Differences in the land use data?
• Differences in process representation– regrowth, soil turnover, ...
• Different vegetation types are cleared?
• Differences in the land use data?
• Differences in process representation– regrowth, soil turnover, ...
• Different vegetation types are cleared?
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0
0,5
1
1,5
2
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
HRBM IBIS LPJ TEM
0
0,5
1
1,5
2
1920 1930 1940 1950 1960 1970 1980 1990
Car
bon
Em
issi
ons
(Pg-
C/y
r)
HRBM IBIS LPJ TEM
CCMLP Land Use FluxCCMLP Land Use Flux
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ConclusionsConclusions
• There are now two different estimates of carbon emissions due to land use
• The disagreement between the estimates is related to:– Differences in land conversion rates– Differences in process representation
• Inverse estimates of the missing carbon sink are critically dependent on estimates of land use carbon emissions
• There are now two different estimates of carbon emissions due to land use
• The disagreement between the estimates is related to:– Differences in land conversion rates– Differences in process representation
• Inverse estimates of the missing carbon sink are critically dependent on estimates of land use carbon emissions