Raymond Desjardins - Impacto de la agricultura sobre el cambio climático

The Impact of Agriculture on
Climate Change
Raymond L. Desjardins, D. Worth, W. Smith, B. Grant, A. VanderZaag, X. Verge,
J. Dyer, A. Betts, H. Letailleur, E. Pattey, B. G. McConkey, C. Monreal
Agriculture and Agri-Food Canada
Ottawa, ON Canada
Presented at the Symposium on Beneficial Microbes for
Agriculture and Biosphere Protection
Madrid, Spain May 20- 21, 2014

2
Outline
•The Earth’s global radiation budget
•Anthropogenic influence on past GHG concentration
•Impact of land use on climate radiative forcing
•Potential impact of agriculture on future radiative forcing
•Summary
•Summary

3
Surface Energy Budget
Atmosphere
Land
Sensible
Heat Flux
(H)
Latent
Heat Flux
(LE)
Incoming
Shortwave
Radiation
(S )
Reflected
Shortwave
Radiation
(S )
Incoming
Longwave
Radiation
(L )
Outgoing
Longwave
Radiation
(L )
Net Radiation (Rn) = S - S + L - L
Albedo (α) =
S
SRn = LE + H + GRn = LE + H + G
Ground
Heat Flux
(G)

4
The Earth’s Global Energy Budget
Source: Trenberth et al. (2009)

5
Greenhouse gas and Climate Change
What does “Radiative Forcing” mean?
• Earth receives approximately 341 W m-2
of solar energy (mean over seasons)
• ~30% reflected away (average Earth albedo of 0.3), remaining 239 W m-2
absorbed
• Surface emits 396 W m-2
as long-wave radiation, 90% is absorbed & re-
emitted by atmospheric greenhouse gases, 239 W m-2
emerges from the top
of the atmosphere
• Radiative forcing is the net change in radiation as the result of a change
imposed upon the Earth-Atmosphere system
• Consequence: 1 W m-2
extra forcing → ~0.5° mean air temp increase
• A change in albedo of ≈ 0.5% results in a change in radiative forcing equal to
1.7 W m-2
• Earth receives approximately 341 W m-2
of solar energy (mean over seasons)
• ~30% reflected away (average Earth albedo of 0.3), remaining 239 W m-2
absorbed
• Surface emits 396 W m-2
as long-wave radiation, 90% is absorbed & re-
emitted by atmospheric greenhouse gases, 239 W m-2
emerges from the top
of the atmosphere
• Radiative forcing is the net change in radiation as the result of a change
imposed upon the Earth-Atmosphere system
• Consequence: 1 W m-2
extra forcing → ~0.5° mean air temp increase
• A change in albedo of ≈ 0.5% results in a change in radiative forcing equal to
1.7 W m-2

Reflected by
Surface
Absorbed by
Atmosphere
Reflected by
Clouds and
Atmosphere
Reflected Shorwave
Radiation
Back
Radiation
Greenhouse
Gases
Atmospheric
Window
Incoming Shortwave
Radiation
Outgoing
Longwave
Radiation
Earth’s global mean annual energy balance (W m-2
)
101.9
100.0
78
75
341.3
340.2
238.5
239.7
356
398
161
165
23
23
79
74.7
Absorbed by
Surface
Surface
Radiation
Absorbed by
Surface
Modified from Trenberth et al. (2009)
Trenberth et al. (2009)
Stephens et al. (2012)
Estimates By:
100 =
100 =
Surface
Imbalance
+ 0.9
+ 0.6
Emitted by
Atmosphere
80
88
17
24
Latent
Heat
Sensible
Heat
396
398
333
345.6

The impact of a change in the surface albedo on the energy
budget and on air temperature (Betts, Desjardins et al. 2014)
RnSnow-free = RnSnow-covered - 50 Wm-2
Soil
Snowpack
Fall-winter snow transition
Soil
Shortwave
radiation
Longwave
radiation
Increased
Albedo:
69% of
impact
Decreased
incoming
longwave
radiation: 31%
of impact

The impact of a change in the surface albedo on the energy
budget and on air temperature
We recently estimated that with the fall-winter snow transition in the
Canadian Prairies, the net radiation at the surface is reduced by 50
Wm-2
, with 69% coming from the reduced net shortwave flux, resulting
from the increased surface albedo and a small increase in effective
cloud albedo, and 31% from reduced incoming long wave radiation.
This difference in net radiation is enough to reduce the air temperature
near the surface by approximately 11 ˚C.
We also showed that for every 10% decrease in days with snow cover
over the Canadian Prairies, the mean October to April air temperature
is warmer by 1.4 C
We recently estimated that with the fall-winter snow transition in the
Canadian Prairies, the net radiation at the surface is reduced by 50
Wm-2
, with 69% coming from the reduced net shortwave flux, resulting
from the increased surface albedo and a small increase in effective
cloud albedo, and 31% from reduced incoming long wave radiation.
This difference in net radiation is enough to reduce the air temperature
near the surface by approximately 11 ˚C.
We also showed that for every 10% decrease in days with snow cover
over the Canadian Prairies, the mean October to April air temperature
is warmer by 1.4 C
Source: Betts, A.K., R. Desjardins, D. Worth, S. Wang and J. Li (2014), Coupling of winter climate transitions to
snow and clouds over the Prairies. J. Geophys. Res. Atmos., 119, 1118-1139, doi:10.1002/2013JD021168.

9
Outline
•Anthropogenic influence on past CO2 & CH4 concentrations
•Potential impact of agriculture on future climate radiative forcing
•Summary
•Potential impact of agriculture on future climate radiative forcing
•Summary

10
Development of Anthropogenic Climate Change
Hypothesis
Vladimir Ivanovich Vernadsky, 1920’s, argued that living beings
could collectively reshape the planet, similar to physical forces
Vladimir Ivanovich Vernadsky, 1920’s, argued that living beings
could collectively reshape the planet, similar to physical forces
Guy Stewart Callandar, 1938, linked increasing surface
temperature between 1890 and 1938 to increasing atmospheric
CO2
Guy Stewart Callandar, 1938, linked increasing surface
temperature between 1890 and 1938 to increasing atmospheric
CO2
Svante Arrhenius, 1896, argued that a doubling of atmospheric
CO2 could bring about a global increase in temperature
amounting to 5-6 ºC
Svante Arrhenius, 1896, argued that a doubling of atmospheric
CO2 could bring about a global increase in temperature
amounting to 5-6 ºC
John Tyndall, 1859, discovered the absorptive properties of
water vapour and carbon dioxide
John Tyndall, 1859, discovered the absorptive properties of
water vapour and carbon dioxide

11
Source: Ruddiman (2003)
Prehistoric Trend in Atmospheric CH4 Shows
Evidence of Anthropogenic Influence
Historic trend in atmospheric CH4
concentration and insolation at
30 ºN, consistent with orbital
monsoon theory
Historic trend in atmospheric CH4
concentration and insolation at
30 ºN, consistent with orbital
monsoon theory
In the past 7,500 years, this
coherent relationship broke
down, and insolation decreased
towards a minima, whereas CH4
increased. Ruddiman (2003)
postulated that this anomalous
increase in CH4 is related to the
development of ‘wet rice’ farming
in China and India
In the past 7,500 years, this
coherent relationship broke
down, and insolation decreased
towards a minima, whereas CH4
increased. Ruddiman (2003)
postulated that this anomalous
increase in CH4 is related to the
development of ‘wet rice’ farming
in China and India
250 ppb increase in CH4
attributed to early rice farming
250 ppb increase in CH4
attributed to early rice farming

12
Atmospheric Methane Concentration
Source: IPCC (2007)

13
Prehistoric Trend in Atmospheric CO2 Shows
Evidence of Anthropogenic Influence
Source: Ruddiman (2003)
An anomalous increase of 40 ppm in
the historic atmospheric CO2
concentration was observed.
An anomalous increase of 40 ppm in
the historic atmospheric CO2
concentration was observed.
Natural explanations for the
increase in CO2 such as natural
biomass loss and a change in ocean
carbonate chemistry were refuted
and it was argued that forest
clearance in Eurasia accounted for
the anomalous increase in CO2
concentration (224- 245 Gt C).
Natural explanations for the
increase in CO2 such as natural
biomass loss and a change in ocean
carbonate chemistry were refuted
and it was argued that forest
clearance in Eurasia accounted for
the anomalous increase in CO2
concentration (224- 245 Gt C).

14
Atmospheric GHG Concentration
Source: IPCC (2007)

15
Outline
•Summary
•Summary

16
Climate Forcing
Greenhouse gases
Biogeochemical
impact
Land-use change
Biogeophysical
impact
Source: IPCC (2013)

17
Radiative forcing and albedo
In recognition of the linkage between climate and surface
albedo, the Third Assessment Report of the IPCC identified
change in surface albedo, associated with land use change,
among the key factors influencing climate radiative forcing,
amounting to about -0.15 Wm-2
.
The IPCC also identified the radiative forcing of albedo due to
land use change as having a low level of scientific
understanding.
In recognition of the linkage between climate and surface
albedo, the Third Assessment Report of the IPCC identified
change in surface albedo, associated with land use change,
among the key factors influencing climate radiative forcing,
amounting to about -0.15 Wm-2
.
The IPCC also identified the radiative forcing of albedo due to
land use change as having a low level of scientific
understanding.

18
1950 - “natural”
1950 forcing relative to
“natural”
global mean: -0.18 Wm-2
Global Change in Albedo due to Land-Use
Change
Source: Betts et al. (2007)
1990 - “natural”
1990 forcing relative to
“natural”
global mean: -0.24 Wm-2
As a result of the land use change, northern mid-latitude
agricultural regions are simulated to be about 1-2 ºC cooler in
winter and spring as compared to the their natural state.
As a result of the land use change, northern mid-latitude
agricultural regions are simulated to be about 1-2 ºC cooler in
winter and spring as compared to the their natural state.

19
Differences in net radiation between forest and grasslands
Conifer – Grass: Rnet
Mean annual difference
= 14 Wm-2
Deciduous – Grass: Rnet
Mean annual difference
= 2 Wm-2
Source: Betts, Desjardins et al. 2007

AgroecosystemsAgroecosystems
ClimateClimate
Biogeophysical
Albedo
Roughness
Hydrology
Biogeophysical
Albedo
Roughness
Hydrology
Biogeochemical
Nutrients, Carbon
Pools
Biogeochemical
Nutrients, Carbon
Pools
Latent and
sensible heat
fluxes
CO2, CH4, N2O
Emissions
Temperature,
Water
Relations
Impact of agriculture on climate

Atmosphere
Animals
Rice Fossil FuelPlants
Waste
Soil
CO2 CO2
CO2
CH4
N2O
CO2
CH4
CH4
CO2
CH4
N2O
CO2
CH4
N2O
Agricultural GHG Emissions

22
Contribution of Agriculture to GHG Concentration
Agricultural lands occupy 37% of the earth’s land surface
Agriculture accounts for 52 and 84% of global anthropogenic methane and
nitrous oxide emissions- It can be a source or sink of carbon dioxide
Agricultural lands occupy 37% of the earth’s land surface
Agriculture accounts for 52 and 84% of global anthropogenic methane and
nitrous oxide emissions- It can be a source or sink of carbon dioxide
Global
Direct farming
activities
13-15% of Global
GHG Emissions
Direct farming
activities + land
use change
18-32% of Global
GHG Emissions
Source: US EPA (2006); FAO (2006); Bellarby et al (2008)

Global GHG emissions
• It is estimated that between 1750 to 1970
emissions of CO2 from agricultural soils are about
equal to the fossil fuel emissions during that time
• Current global GHG emissions are about 49 Gt
CO2e y-1
, 74% of which are CO2, 16% CH4 and
10% N2O
• CO2concentration is increasing at 2 ppmv y-1
that
is 6 Pg C y-1
or 6 Gt C y-1
or 22 Gt CO2 y-1
23

24
Impact of Present-Day Agriculture on Deforestation
• Forests account for 25% of the land area 75% of C in
vegetation and 40% of carbon in soil
• Deforestation produces 5.9 Gt CO2 y-1
, 17% of annual
anthropogenic GHG emissions
• CO2 is released from organic matter decomposition
where soil C is metabolized by soil microorganisms to
CH4 and CO2 and is released to the atmosphere.
• Tropical deforestation takes place mainly for large-scale
agriculture

Soil C Change in Agricultural Soils (Lal 2003)
• Area of arable land 1,369 Mha
• Permanent pasture 3,460 Mha
• Permanent crops 132 Mha
• Most croplands have lost 30 – 40 Mg C/ha
• It is estimated that agricultural soils have lost
66-90 Pg C
• Global soil C sequestration potential 0.4 - 0.8
Pg C y-1
• Potential 30-60 Pg C over the next 25-50
years
25

Anthropogenic Global Methane Sources-
Beneficial Microbes (2010)
Source: Global Carbon Project 2013; Figure based on Kirschke et al. 2013
Juniper, T. 2013 What has nature ever done for us? Profile books, 324pp.

Source: IPCC 2007
Anthropogenic Global Sources of Nitrous oxide

• Decay of organic matter by microbes in
soil release reactive N
• Biological N fixation- N fixing bacteria
into reactive N
• Application of inorganic fertilizer
28
Sources of Nitrous Oxide

Substantial reduction in greenhouse gas emission
intensities of Canadian agricultural products
0
2
4
6
8
10
12
14
16
18
GHGemissionsperkilogramofmilkorliveweight
producedordozeneggs
1981 1986 1991
1996 2001 2006
Source: Dyer et al (2008); Vergé et al (2008); Vergé et al (2009a; 2009b)
Milk
-26%
Beef
-56%
Pork
-56%
Poultry -
broiler meat
-19%
Poultry - eggs
-8%
Improved breeds, adoption of BMPs such as no-tillage and increased feeding of
leguminous crops have led to a reduction in emissions intensity dairy, beef and
pork production in Canada.
Improved breeds, adoption of BMPs such as no-tillage and increased feeding of
leguminous crops have led to a reduction in emissions intensity dairy, beef and
pork production in Canada.

Carbon footprint of animal products per unit
of protein
Source: Dyer, Desjardins et al (2010)
One of the primary functions of
animal products is to provide protein
for growth. Therefore, expressing the
carbon footprint per unit of protein is
one way to compare emissions
between animal types.

32
0
2
4
6
8
10
12
14
16
Perennial crops Summerfallow No-Tillage
Area(millionha)
1981 1986 1991 1996 2001 2006
0
2
4
6
8
10
12
14
16
Area(millionha)
1981 1986 1991 1996 2001 2006
What is the impact of a decrease in area under summerfallow on the
air temperature on the Canadian Prairies?
What is the impact of a decrease in area under summerfallow on the
air temperature on the Canadian Prairies?
Trends in Agricultural Management Practices in Canada

33
Rn
Bare Soil
Vegetated Surface
Rn
zi=2-3 km
zi=0.5 km
G G
H LE
H LE
Effects of Leaving the Land Surface Bare for a
Summer on the Energy Budget
Source: Gameda et al. (2007)
Bare
Soil
Vegetated
LE - +
H + -
G + -
zi + -

34
Impact of Summerfallow on Climate: Mean
Daily Maimum Air Temperature
1951-1975: Increasing
levels of summerfallow
8.7 Mha-11.4 Mha
T max increasing over
time
1951-1975: Increasing
8.7 Mha-11.4 Mha
T max increasing over
time
1976-2000: Declining
11.4 Mha-5.4 Mha
T max decreasing over
time
1976-2000: Declining
11.4 Mha-5.4 Mha
T max decreasing over
time
Source: Gameda et al 2007
On the Canadian prairies, the elimination of 6 Mha of
summerfallow has been associated with a period of time when
June 15 to July 15 mean daily maximum temperature has
decreased, likely due to a decrease in the sensible heat flux and
an increase in evapotranspiration. This analysis shows that
reduction of summer fallowing has caused a reduction in
maximum air temperature of 1.7 C per decade during the
mid- June to mid-July period.
On the Canadian prairies, the elimination of 6 Mha of
summerfallow has been associated with a period of time when
June 15 to July 15 mean daily maximum temperature has
decreased, likely due to a decrease in the sensible heat flux and
an increase in evapotranspiration. This analysis shows that
reduction of summer fallowing has caused a reduction in
maximum air temperature of 1.7 C per decade during the
mid- June to mid-July period.

35
0
2
4
6
8
10
12
14
16
Area(millionha)
1981 1986 1991 1996 2001 2006
0
2
4
6
8
10
12
14
16
Area(millionha)
1981 1986 1991 1996 2001 2006
What are the combined biogeochemical and biogeophysical impacts
of a decrease in area of summerfallow in the Canadian Prairies in
terms of climate radiative forcing?
What are the combined biogeochemical and biogeophysical impacts
of a decrease in area of summerfallow in the Canadian Prairies in
terms of climate radiative forcing?
Trends in Agricultural Management Practices in Canada

36
How to calculate net reflected shortwave radiation?
Absorbed shortwave radiation in Wm−2
(a) is estimated as:Absorbed shortwave radiation in Wm−2
(a) is estimated as:
)()1( IIa αβα +−=
aINRS −=
where I is the incoming shortwave flux (Wm−2
),
α is the albedo, and
β is a coefficient to correct for the atmospheric absorption of
reflected short wave flux
The net reflected shortwave radiation can be calculated as
follows:
where I is the incoming shortwave flux (Wm−2
),
α is the albedo, and
β is a coefficient to correct for the atmospheric absorption of
reflected short wave flux
The net reflected shortwave radiation can be calculated as
follows:
where NRS is the net reflected shortwave radiation (Wm−2
)where NRS is the net reflected shortwave radiation (Wm−2
)

37
where Ar is the area of the region of interest and Ae is the
Earth’s surface area, and subscript 1 and 2 refers to the
different land cover types
The equivalent radiative forcing of carbon can be determined using
following equation (Betts 2000)
where Ar is the area of the region of interest and Ae is the
Earth’s surface area, and subscript 1 and 2 refers to the
different land cover types
The equivalent radiative forcing of carbon can be determined using
following equation (Betts 2000)
erR AANRSNRS /)( 21 −=δ
where C0 is the atmospheric CO2 concentration (397 ppmv),
and ΔC is the change in atmospheric CO2 concentration
where C0 is the atmospheric CO2 concentration (397 ppmv),
and ΔC is the change in atmospheric CO2 concentration
)/1(35.5 0CCLnRFC ∆+=
The differences in reflected shortwave radiation for various land
cover types affect the local radiation budget. This effect on
global radiative forcing can be estimated for a given region of
interest by
The differences in reflected shortwave radiation for various land
cover types affect the local radiation budget. This effect on
global radiative forcing can be estimated for a given region of
interest by
How is a change in soil carbon related to a change in albedo?

38
For the reduction in summerfallowing in the province of Saskatchewan for the period between 1971 and
2006, we estimated a net radiative forcing of -0.160 mWm−2
of which 67% of this effect was due to a
change in albedo and the remainder to soil C sequestration

39
Agricultural Practice Biogeophysical
effect
Biogeochemical
effect
Net Effect
Reduced tillage + _ _ _ − −
Afforestation + + _ _ _ _
Deforestation − − + + + +
Plant forage crops − − − − −
Irrigation − − + −
Biochar + − − −
Leaf albedo bio-
geoengineering
− − − −
Biofuel − − + −
Synchronize N availability
to N use by crops
− − − −
Reduced fallow - -- − − − − −
Plant fall crops − − − −
Leave long stubble for
snow trapping
− − − −
Biophysical and Biochemical Forcing of
Agricultural Management Practices

40
Outline
•Summary
•Summary

Source: Lal (2003); Verge et al. 2007
Carbon Sequestration in Agricultural Soils
Carbon sequestration is the process of removing carbon from the
atmosphere and depositing it in a reservoir.
Global potential for carbon sequestration in agricultural soils is estimated at
30-60 Pg C over the next 50 years, through the adoption of BMPs and
restoration of degraded soils. Impact of climate change
Carbon sequestration is the process of removing carbon from the
atmosphere and depositing it in a reservoir.
Global potential for carbon sequestration in agricultural soils is estimated at
30-60 Pg C over the next 50 years, through the adoption of BMPs and
restoration of degraded soils. Impact of climate change
However, carbon sequestration is dependent upon the continuation of the
management practice and the climatic conditions under which it was
sequestered. Carbon sequestration is a reversible process.
However, carbon sequestration is dependent upon the continuation of the
management practice and the climatic conditions under which it was
sequestered. Carbon sequestration is a reversible process.
Recent estimates of projected climate change suggest that in the future
Canadian agricultural soils could be a source of carbon, amounting to 53-
160 Mt C, depending on the climate change scenario.
Recent estimates of projected climate change suggest that in the future
Canadian agricultural soils could be a source of carbon, amounting to 53-
160 Mt C, depending on the climate change scenario.

42
Biodigestion of Animal Wastes and Crop
Residues
Current estimates of the maximum annual methane production potential
from the biodigestion of animal manure in Canada (≈ 2.3 × 109
m3
) have the
energetic equivalent of 1% of annual fossil energy demand.
Current estimates of the maximum annual methane production potential
from the biodigestion of animal manure in Canada (≈ 2.3 × 109
m3
) have the
energetic equivalent of 1% of annual fossil energy demand.
Source: Levin et al. (2007)
However, current technical and economic factors limit the total energy
production from these sources to much less than the maximum potential.
However, current technical and economic factors limit the total energy
production from these sources to much less than the maximum potential.

43
Bioenergy
Thousands of biodigesters are being built all over the
world.
Thousands of biodigesters are being built all over the
world.
Is this a way to ensure the sustainability of agricultural
production?
Is this a way to ensure the sustainability of agricultural
production?

44
Production of Ethanol from Corn
Ethanol production, especially from corn, has received
considerable attention in the popular and scientific literature.
Ethanol production, especially from corn, has received
considerable attention in the popular and scientific literature.
Current life cycle analysis estimates that corn ethanol production reduces GHG
emissions by ≈ 10-20%, relative to conventional gasoline. However, if emissions
from land use change are considered (which is necessary to produce food that
has been diverted for fuel), emissions are greater for ethanol production than for
gasoline production.
Current life cycle analysis estimates that corn ethanol production reduces GHG
emissions by ≈ 10-20%, relative to conventional gasoline. However, if emissions
from land use change are considered (which is necessary to produce food that
has been diverted for fuel), emissions are greater for ethanol production than for
gasoline production.
Source: Farrell et al. (2006); Searchinger et al. (2008)
Development of cellulosic ethanol
offers the potential to significantly
reduce GHG emissions as
compared to gasoline.
Development of cellulosic ethanol
offers the potential to significantly
reduce GHG emissions as
compared to gasoline.

45
Bioenergy
•Low carbon energy biofuels, bioenergy
e.g. ethanol biofuel production in the US
•Low carbon energy biofuels, bioenergy
e.g. ethanol biofuel production in the US
The target in the US for
2020 is 144 billion
liters/year, 60% is to come
from non-grain sources.
This means that 48 Mha
will be required. This
should cause the most
rapid change in land use
in US history.
The target in the US for
2020 is 144 billion
liters/year, 60% is to come
from non-grain sources.
This means that 48 Mha
will be required. This
should cause the most
rapid change in land use
in US history.
Sinclair 2009

The meat consumption in the world in 2010
46
Consumption of meat in 2010: 286.2 million tonnes
Consumption rate has increased constantly for 50 years: 2.3% for the past
decade
Consumption of meat in 2010: 286.2 million tonnes
Consumption rate has increased constantly for 50 years: 2.3% for the past
decade
Beef
Pork
Poultry
FranceAgrimer 2011, FAO 2010
South America
Central America
North America
Global repartition (%)
Europe
Asia
OceaniaAfrica

Substantial reduction in greenhouse gas emission
intensities of Canadian agricultural products
0
2
4
6
8
10
12
14
16
18
GHGemissionsperkilogramofliveweight
produced
1981 1986 1991
1996 2001 2006
Source: Dyer et al (2008); Vergé et al (2008); Vergé et al (2009a; 2009b)
Beef
-56%
Pork
-56%
Poultry -
broiler meat
-19%

Change in beef, pork and poultry consumption
48
Source: FAO, 2010
Considering the GHG emissions for each type of meat production, the
GHG emissions in 2010 were about 3.7 Gt CO2e.
By 2040 the GHG emissions due to meat consumption would be about
5.1 Gt CO2e if the growth rate remains the same. Hence, even if the
beef consumption is decreasing, it still does not offset the increase in
GHG emissions due to the predicted increase in population.
Considering the GHG emissions for each type of meat production, the
GHG emissions in 2010 were about 3.7 Gt CO2e.
By 2040 the GHG emissions due to meat consumption would be about
5.1 Gt CO2e if the growth rate remains the same. Hence, even if the
beef consumption is decreasing, it still does not offset the increase in
GHG emissions due to the predicted increase in population.

49
Crop Bioengineering
Recent research has estimated that if the albedo of global croplands could
be increased by 0.04, then a global cooling of approximately 0.1 ºC could
be achieved, with regional cooling in the continental northern hemisphere of
1 ºC during the summer months.
Recent research has estimated that if the albedo of global croplands could
be increased by 0.04, then a global cooling of approximately 0.1 ºC could
be achieved, with regional cooling in the continental northern hemisphere of
1 ºC during the summer months.
Source: Ridgwell et al. (2009)

50
How can we assess the impact of agricultural
land management on biophysical forcing?
1. Identify fields with known crop type and management, estimate annual
albedo from satellite imagery and scale up to national scale using
crop/management distribution
1. Identify fields with known crop type and management, estimate annual
albedo from satellite imagery and scale up to national scale using
crop/management distribution
Canada
Spring wheat, no till
Barley, min till
Summerfallow

Synchronizing the Release of Fertilizer-N with Crop Uptake
Improving nitrogen use efficiency by crops
(Use Chemical Signals from Root Exudates
for N release on crop demand C. Monreal)
0
0.4
0.8
1.2
1.6 Crop N uptake
INF-N release
0
25
50
100
75
Growing season (# of days)
CropNUptake(kgN/ha/day)
Rootexudatecontent(micrograms/ml)
Root exudate

52
Microorganisms and climate change
It is unclear
whether changes in
microbial processes
lead to a net
positive or negative
feedback for GHG
emissions.
It is unclear
whether changes in
microbial processes
lead to a net
positive or negative
feedback for GHG
emissions.
•Microbial processes have a central role in the global fluxes of carbon
dioxide, methane and nitrous oxide and are likely to respond rapidly to
climate change.
•There are millions of microorganisms (nematodes, microbes, etc.) in every
teaspoonful of soil. It is important to understand the mechanisms by which
they regulate GHG fluxes from agricultural sources.
•It is a tantalizing prospect for mitigating climate change for the future.
•Microbial processes have a central role in the global fluxes of carbon
dioxide, methane and nitrous oxide and are likely to respond rapidly to
climate change.
•There are millions of microorganisms (nematodes, microbes, etc.) in every
teaspoonful of soil. It is important to understand the mechanisms by which
they regulate GHG fluxes from agricultural sources.
•It is a tantalizing prospect for mitigating climate change for the future.

53
Key Points
•Agriculture is significantly altering the Earth’s energy budget and climate
in a variety of ways
•Because of the large spatial extent and intensive management,
agriculture has contributed and continues to contribute to climate change
through both biogeochemical and biogeophysical mechanisms
•The main role of agriculture is to produce food and presently food
production accounts for about 15-20% of the GHG emissions
•The potential exist in agriculture to reduce GHG emissions and increase
soil carbon sequestration
•The potential impact of soil C sequestration is large but finite and climate
change is likely to make sequestering C very difficult
•Microorganisms play a very important role in the biogeochemical
mecanisms
• Can mankind harness microbial process to help manage climate
change?
•Agriculture is significantly altering the Earth’s energy budget and climate
in a variety of ways
•Because of the large spatial extent and intensive management,
agriculture has contributed and continues to contribute to climate change
through both biogeochemical and biogeophysical mechanisms
•The main role of agriculture is to produce food and presently food
production accounts for about 15-20% of the GHG emissions
•The potential exist in agriculture to reduce GHG emissions and increase
soil carbon sequestration
•The potential impact of soil C sequestration is large but finite and climate
change is likely to make sequestering C very difficult
•Microorganisms play a very important role in the biogeochemical
mecanisms
• Can mankind harness microbial process to help manage climate
change?

54
References
Betts, A. K., Desjardins, R. L. and D. Worth 2007. Impact of agriculture, forest and cloud feedback on the surface energy
budget in BOREAS. Agricultural and Forest Meteorology 142:156-169.
Betts, R. A., Falloon, P. D., Goldewijk, K. K. and N. Ramankutty. 2007. Biogeophysical effects of land use on climate:
Model simulations of radiative forcing and large-scale temperature change. Agricultural and Forest Meteorology
142:216-233.
Betts, A.K., R. Desjardins, D. Worth, S. Wang and J. Li 2014. Coupling of winter climate transitions to snow and clouds
over the Prairies. J. Geophys. Res. Atmos., 119, 1118-1139, doi:10.1002/2013JD021168.
Desjardins, R.L., J.C. Keng and K. Haugen-Kozyra. (editors) 1999. Proceedings on the international workshop on reducing
nitrous oxide emissions from agroecosystems. Banff, Alberta, Mar 3-5. Agriculture and Agri-Food Canada, Research Branch;
Alberta Agriculture, Food and Rural Development, Conservation and Development Branch. 256 pp.
Desjardins, R.L., Sivakumar, M.V.K. and C. de Kimpe 2007. The contribution of agriculture to the state of climate:
Workshop summary and recommendations. Agric. and Forest Meteorology. 142: 314-324.
Desjardins, R.L. 2010. The impact of agriculture on climate change. In the proceedings of the North American
Biotechnology Conference (NABC) 21. Adapting Agriculture to Climate Change, Saskatoon, Saskatchewan. pp 29- 39.
Dyer, J.A., X.P.C. Vergé, R.L. Desjardins and D.E. Worth 2010. The protein-based GHG emission intensity for livestock
products in Canada. Journal of Sustainable Agriculture. 34(6):618-629. Doi:10.1080/10440046.2010.493376.
Gameda, S., Qian, B., Campbell, C. and R.L. Desjardins 2007. Climatic trends associated with summerfallow in the
Canadian Prairies. Agricultural and Forest Meteorology 142:170-185.
Hutchinson, J.J., Campbell, C.A., and R.L. Desjardins 2007. Some perspectives on carbon sequestration in agriculture.
Agricultural and Forest Meteorology 142: 288- 302.
Juniper, T. 2013. What has nature ever done for us? Profile books, 324pp.
Betts, A. K., Desjardins, R. L. and D. Worth 2007. Impact of agriculture, forest and cloud feedback on the surface energy
budget in BOREAS. Agricultural and Forest Meteorology 142:156-169.
Betts, R. A., Falloon, P. D., Goldewijk, K. K. and N. Ramankutty. 2007. Biogeophysical effects of land use on climate:
Model simulations of radiative forcing and large-scale temperature change. Agricultural and Forest Meteorology
142:216-233.
Betts, A.K., R. Desjardins, D. Worth, S. Wang and J. Li 2014. Coupling of winter climate transitions to snow and clouds
over the Prairies. J. Geophys. Res. Atmos., 119, 1118-1139, doi:10.1002/2013JD021168.
Desjardins, R.L., J.C. Keng and K. Haugen-Kozyra. (editors) 1999. Proceedings on the international workshop on reducing
nitrous oxide emissions from agroecosystems. Banff, Alberta, Mar 3-5. Agriculture and Agri-Food Canada, Research Branch;
Alberta Agriculture, Food and Rural Development, Conservation and Development Branch. 256 pp.
Desjardins, R.L., Sivakumar, M.V.K. and C. de Kimpe 2007. The contribution of agriculture to the state of climate:
Workshop summary and recommendations. Agric. and Forest Meteorology. 142: 314-324.
Desjardins, R.L. 2010. The impact of agriculture on climate change. In the proceedings of the North American
Biotechnology Conference (NABC) 21. Adapting Agriculture to Climate Change, Saskatoon, Saskatchewan. pp 29- 39.
Dyer, J.A., X.P.C. Vergé, R.L. Desjardins and D.E. Worth 2010. The protein-based GHG emission intensity for livestock
products in Canada. Journal of Sustainable Agriculture. 34(6):618-629. Doi:10.1080/10440046.2010.493376.
Gameda, S., Qian, B., Campbell, C. and R.L. Desjardins 2007. Climatic trends associated with summerfallow in the
Canadian Prairies. Agricultural and Forest Meteorology 142:170-185.
Hutchinson, J.J., Campbell, C.A., and R.L. Desjardins 2007. Some perspectives on carbon sequestration in agriculture.
Agricultural and Forest Meteorology 142: 288- 302.
Juniper, T. 2013. What has nature ever done for us? Profile books, 324pp.

55
References
Lal, R. 2003. Global potential of soil carbon sequestration to mitigate the greenhouse effect. Critical Reviews in Plant
Sciences 22:151-184.
Ridgwell, A., Singarayer, J. S., Hetherington, A. M. and P.J. Valdes 2009. Tackling regional climate change by leaf albedo
bio-geoengineering. Current Biology 19:146-150.
Ruddiman, W. F. 2003. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61:261-293.
Searchinger, T., Heimlick, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D. and T. H. Yu 2008.
Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change. Science
319:1238-1240.
Sinclair, T. R. 2009. Taking measure of biofuel limits. American Scientist 97.5: 400-407.
Smith, W. N., Grant, B. B., Desjardins, R. L., Qian, B., Hutchinson, J. J. and S. Gameda 2009. Potential impact of climate
change on carbon in agricultural soils in Canada 2000-2099. Climatic Change 93:319-333.
Stehfest, E., Bouwman, L., van Vuuren, D. P., den Elzen, M. G. J., Eickhout, B. and Kabat, P. 2009. Climate benefits of
changing diet. Climatic Change In press:DOI 10.1007/s10584-008-9534-6.
Stephens, G.L.. Campbell, G.G. and Vonder Haar, T.H. 2012. Earth radiation budgets, J, . Geophys. Res., 86(C10),9739-
9760.
Trenberth, K. E., Fasullo, J. T. and Kiehl, J. 2009. Earth's global energy budget. Bulletin of the American Meteorological
Society 90(3):311-323.
Vergé, X.P.C., de Kimpe, C. and R.L. Desjardins, 2007. Agricultural production, greenhouse gas emissions and
mitigation potential. Agricultural and Forest Meteorology 142: 255- 269.
Vergé, X.P.C., Dyer, J.A., Desjardins, R.L., and Worth, D. 2008. Greenhouse gas emissions from the Canadian Beef Industry. Agricultural Systems.
98 (2): 126-134.
Vergé, X.P.C., Dyer, J.A., Worth, D.E., Smith, W.N., Desjardins, R.L., and B.G. McConkey. 2012. A greenhouse gas and
soil carbon model for estimating the carbon footprint of livestock production in Canada. Animals, 2: 437-454;
doi:10.3390/ani2030437.
Lal, R. 2003. Global potential of soil carbon sequestration to mitigate the greenhouse effect. Critical Reviews in Plant
Sciences 22:151-184.
Ridgwell, A., Singarayer, J. S., Hetherington, A. M. and P.J. Valdes 2009. Tackling regional climate change by leaf albedo
bio-geoengineering. Current Biology 19:146-150.
Ruddiman, W. F. 2003. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61:261-293.
Searchinger, T., Heimlick, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D. and T. H. Yu 2008.
Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change. Science
319:1238-1240.
Sinclair, T. R. 2009. Taking measure of biofuel limits. American Scientist 97.5: 400-407.
Smith, W. N., Grant, B. B., Desjardins, R. L., Qian, B., Hutchinson, J. J. and S. Gameda 2009. Potential impact of climate
change on carbon in agricultural soils in Canada 2000-2099. Climatic Change 93:319-333.
Stehfest, E., Bouwman, L., van Vuuren, D. P., den Elzen, M. G. J., Eickhout, B. and Kabat, P. 2009. Climate benefits of
changing diet. Climatic Change In press:DOI 10.1007/s10584-008-9534-6.
Stephens, G.L.. Campbell, G.G. and Vonder Haar, T.H. 2012. Earth radiation budgets, J, . Geophys. Res., 86(C10),9739-
9760.
Trenberth, K. E., Fasullo, J. T. and Kiehl, J. 2009. Earth's global energy budget. Bulletin of the American Meteorological
Society 90(3):311-323.
Vergé, X.P.C., de Kimpe, C. and R.L. Desjardins, 2007. Agricultural production, greenhouse gas emissions and
mitigation potential. Agricultural and Forest Meteorology 142: 255- 269.
Vergé, X.P.C., Dyer, J.A., Desjardins, R.L., and Worth, D. 2008. Greenhouse gas emissions from the Canadian Beef Industry. Agricultural Systems.
98 (2): 126-134.
Vergé, X.P.C., Dyer, J.A., Worth, D.E., Smith, W.N., Desjardins, R.L., and B.G. McConkey. 2012. A greenhouse gas and
soil carbon model for estimating the carbon footprint of livestock production in Canada. Animals, 2: 437-454;
doi:10.3390/ani2030437.

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