Transcript Document

Land Use Emissions, Rice &
Climate Change
Yaqiu Li
Jiangfeng Wei
Yan Zhang
Wenyan Yu
Outline
 Land-use emissions
 Rice and methane
 Climate change effects on rice
Land use
“The total of arrangements, activities, and inputs that people
undertake in a certain land cover type.”
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Peri-Urban Land
Wetlands
Cropland
Agroforestry Land
Rangeland/Grasslands
Forest Land
Deserts
In sequence of increasing
intensity of use, basically
The Influence of Land Use on Greenhouse
Gas Sources and Sinks
 Land-use emissions
 Carbon stocks
 Land-Use Management
land-use main emissions
 CO2 from net deforestation (nearly all)
 CH4 from rice cultivation
 CH4 from enteric fermentation of cattle
 N2O from fertilizer application (80%)
]
(53%)
Emissions of carbon dioxide due to changes in land use mainly come
from the cutting down of forests
Source of CH4
CH4 Source
Mt CH4 yr-1
Gt C-eq yr-1
Livestock
110 (85–130)
0.6 (0.5–0.7)
Rice paddies
60 (20–100)
0.3 (0.1–0.6)
Biomass burning
40 (20–80)
0.2 (0.1–0.5)
Natural wetlands
115 (55–150)
0.7 (0.3–0.9)
N2O Source
N2O Source
Cultivated soils
Mt N2O yr-1
Gt C-eq yr-1
3.5 (1.8–5.3)
0.9 (0.5–1.4)
0.5 (0.2–1)
0.1 (0.05–0.3)
0.4 (0.2–0.5)
0.1 (0.05–0.13)
3 (2.2–3.7)
0.8 (0.6–1)
Natural tropical soils—dry savannas
1 (0.5–2)
0.3 (0.1–0.5)
Natural temperate soils—forests
1 (0.1–2)
0.3 (0.03–0.5)
Natural temperate soils—grasslands
1 (0.5–2)
0.3 (0.1–0.5)
Biomass burning
Livestock (cattle and feed lots)
Natural tropical soils—wet forests
Carbon Stocks
 Land-use change is often associated with
a change in carbon stocks.
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conversion of natural ecosystems to permanent croplands,
conversion of natural ecosystems for shifting of cultivation,
conversion of natural ecosystems to pasture
abandonment of croplands,
abandonment of pastures,
harvest of timber,
establishment of tree plantations
Global carbon stocks in vegetation and top 1 m of soils
Area
(106 km2)
Biome
Carbon Stocks (Gt C)
Vegetation
Soils
Total
Tropical forests
17.6
212
216
428
Temperate forests
10.4
59
100
159
Boreal forests
13.7
88
471
559
Tropical savannas
22.5
66
264
330
Temperate grasslands
12.5
9
295
304
Deserts and semideserts
45.5
8
191
199
Tundra
9.5
6
121
127
Wetlands
3.5
15
225
240
Croplands
16.0
3
128
131
466
2011
2477
Total
151.2
Land use managent
 Vegetation can “sequester” or remove carbon
dioxide from the atmosphere and store it for
potentially long periods in above- and belowground biomass, as well as in soils.
 Soils, trees, crops, and other plants may make
significant contributions to reducing net
greenhouse gas emissions by serving as carbon
“sinks.”
Options for Managing Terrestrial Carbon
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Avoid emissions through the conservation of existing
carbon stocks in forests and otherecosystems, including
in soils (i.e., reducing LULUCF emissions). An example
is reducing the rate of deforestation.
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Sequester additional carbon in forests and other
ecosystems (including in soils), in forest products, and
in landfills (i.e., enhancing LULUCF removals). An
example is planting trees where there have not been
trees in the past (afforestation).
Options for Managing Terrestrial Carbon
 Substitute renewable biomass fuels for fossil fuels (i.e.,
fuel substitution), or use biomass products to replace
products from other materials such as steel or concrete,
that have different, often greater, fossil-fuel
requirements in their production and use (i.e., materials
substitution).
Mean annual carbon emissions from alternative
land-use management options (1991-2001).
Methane and Rice
 1. Methane (CH4) is
second important
greenhouse gas (GHG).
 2. In 100 year period, a
molecular CH4 can
absorb about 25 times
more energy than a
molecular CO2.
Methane emission from rice fields
Global estimates of CH4 emission from rice fields
 1. The source strength of
rice fields in Asia was
estimated to range between
46 and 63 million t/yr of
methane.
 2. Comprising 51% of the
global harvested rice area,
rice fields in China and India
emit 29-40 million t/yr.
 3. Global estimates of rice
field methane production
range up to 100 million t/yr.
Different emission in Asia
 Irrigated rice,
comprised 50%
of total rice
area, accounts
for 80% of
methane
emissions.
Emissions vary in different locations
Sinks
 1. Troposphere &
stratosphere :
 broken down by OH
 Troposphere: 506 Tg/yr
 Stratosphere: 40 Tg/Yr
 2. Soil:
about 30 Tg/yr
Mitigation of effect
 Emission reductions produce an
immediate and significant impact on
climate change
 Why?
Rice Paddies and methyl halides
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Figure 1. Maxwell, California, averaged weekly fluxes during 1998 for methane, methyl
chloride, methyl bromide, and methyl iodide. Arrows indicate maximum tillering (M,
55 DAS), booting (B, 70 DAS), heading (H, 80 DAS), flowering (F, 90 DAS), and the
reflooding date (RF, 45 DAS). The flux for all gases is shown; note differing scales of
emission for each gas. Symbols: , straw-incorporated plots; , burnt straw plots; , controls.
Error bars show one standard deviation.
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Fig. 2. Maxwell, California, averaged weekly fluxes during 1999 for methane, methyl
chloride, methyl bromide, and methyl iodide. Arrows indicate maximum tillering (M,
47 DAS), booting (B, 75 DAS), heading (H, 89 DAS), and flowering (F, 97 DAS). The flux
for all gases is shown; note differing scales of emission for each gas. Symbols: , strawincorporated plots; , burnt straw plots; , controls. Error bars show one standard deviation
The worldwide rice farming contributes
methyl bromide -----1%
methyl iodide -------5%
Impacts of Global Climate Change
on Rice Production
----What the rice paddies looks like from the sky?
----People working in the rice paddies.
The Importance of Rice
 One of the world’s most
important food crops,
staple food for over 50 %
people in this world.
 To meet the demands of a
growing population,
agricultural productivity
must continue to increase.
 If global climate changes
act to reduce food
production, serious, longterm food shortages and
aggravation of societal
problems could result.
Climate Reasons that affect the
Rice Growing
1. Greenhouse Gases and Increased
temperature:
Concentrations of GHGs like CO2 and CH4
have increased significantly since preindustrial
times. The concentrations of these gases have
a powerful influence on the average global
temperature of the planet, and consequently,
on the global climate.
2. Stratospheric Ozone Depletion Effects
on Rice---UV-B Radiation:
. Rice is the world’s most important food crop and
grown mostly in tropical and subtropical countries.
. It is know that UV-B radiation is highest in tropical
regions where rice is grown, because the
stratospheric ozone layer is high latitude, and the
solar angles are higher.
. After preindustrial period, people have release
great amount of ozone decomposing matters, like
chorofluorocarbons (CFCs) which already induced
stratospheric ozone depletion, thus increasing the
incoming UV-B.
Climate Change—
Rice Response to UV-B
Biodiversity
Yield
Biogeochem
Circling
Endpoints
Competition
pest, Pathogen, Decomposition
Ecosystem
Growth,Yield Morphology,
Chemical matters
Whole Plant
Photosynthesis
Carbon Allocation
Tissue
Targets
Molecular
UV-B
known
less known
Effect of UV-B on Rice Yield
Cultivar ‘Lebonnet’
16
Seed dry
weight (g)
14
12
10
8
6
4
2
0
0
16
23
32
Percent UV-B Enhancement
1.Possible trends towards a reduction in seed yield under enhanced
UV-B conditions of ozone depletions of 8 to 16%
(Florida, US, 1984)
2. Rice growth and photosynthesis can be suppressed
by exposure to UV-B under greenhouse conditions.
3. UV-B can induce the accumulation of UV-absorbing
pigments and alter leaf surface characteristics.
But, it is unknown whether these responses are
sufficient to completely protect rice from increased
exposure to UV-B.
4. UV-B can alter plant morphology without reducing
plant biomass. These morphological traits, like tillering,
is known to influence rice yield, UV-B could potentially
alter grain yield without apparent reductions in total
production
5. UV-B radiation changing rice productivity related to
radiation magnitude and direction. And this character
depends on rice cultivar.
6. Results from pilot experiments indicate that UV-B
enhancement can significantly increase the
susceptibility of rice to blast disease.
7. UV-B enhancement is known to alter the competitive
balance between crops and weeds
Global warming —
Effects of CO2 and temperature on
rice production
Effects of CO2 and temperature on the rice
ecosystem
 Increasing atmospheric CO2
stimulates plant growth, the
beneficial effects on rice
growth have been observed for
levels only up to 500 ppm.
Some plant species respond
positively to CO2 levels up to
1,000 ppm.
 The benefits of increased CO2
would be lost if temperatures
also rise. That is because
increased temperature
shortens the period over which
rice grows.
Interactive effects of CO2 and temperature
8000
7000
yield (kg/ha)
6000
5000
4000
3000
2000
570
1000
0
450
0
1
2
3
Temperature change (K)
4
CO2 (ppm)
330
5
(Bachelet et al., 1993)
Indirect effects of global climate change on rice
 Altered timing and magnitude of
precipitation can induce drought or
flood injury
 Increased temperatures, and/or
changes in precipitation could have
dramatic impacts on rice diseases
and insects.
 Enhanced UV-B, enriched CO2
and increased temperatures may all
alter competition between rice and
major weeds, and the contribution
of other organisms to nitrogen
fixation in rice fields.
Models
Both models (ORYZA1, SIMRIW) were potential
production models – i.e. yield determined only by
temperature, sunlight, CO2 level, daylength, crop variety,
planting and harvest dates
Did not take into account:
water limitations
nutrient (N,P,K) limitations
weeds, pests & diseases
Climate scenarios
General Circulation Models (GCMs)
GFDL
Name
Base CO2 (ppm)
Geophysical
Fluid
Dynamics
Laboratory
300
Temperature
change (°
C)
+4.0
Precipitation
change (%)
8
GISS
UKMO
Goddard
United
Institute of
Kingdom
Space Studies Meteorological
Office
300
323
+4.2
+5.2
11
15
Predicted yield changes
GFDL
3 GCM scenarios
% change in regional rice production
predicted by ORYZA1 and SIMRIW under
different GCM scenarios
GFDL
GISS
UKMO
68 weather stations
ORYZA1
+6.5
-4.4
-5.6
(Matthews et al., 1995)
SIMRIW
+4.2
-10.4
-12.8
Model results
 The results of recent international modeling exercises
suggest a mixed future of 2XCO2 for rice production
in Asia, with some countries benefiting and others
losing production.
 Overall, Asian rice production, based on present
varieties and systems, could decline by about 4% in
the climates of the next century.
ENSO and rice production (Sri Lanka)
October to May
May to September
Adaptation options
 Adjusting planting dates to avoid
higher temperatures at flowering
time (warmer regions)
 Breeding temperature tolerant
varieties (warmer regions)
 Transition from single-cropping to
double-cropping where extended
growing season permits (cooler
regions)
 Selection for varieties with
greater response to elevated
CO2 (all regions)
 Breed crop plants tolerant to UVB radiation
Conclusion
 Land use change has an influence on green house
gas sources and sinks.
 Rice paddies are a large source of CH4, an
assessment of the agricultural effects of global
environmental change must include rice as a crop of
primary interest.
 While there is some information regarding the single
effects of UV-B, CO2, temperature and precipitation
on rice, little is know about the interactive effects of
these factors.