Land Use Emissions, Rice & Climate Change

Yaqiu LiJiangfeng Wei

Yan ZhangWenyan 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.”

Peri-Urban Land Wetlands Cropland Agroforestry Land Rangeland/Grasslands Forest Land Deserts

In sequence of increasingintensity 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

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)

Source of CH4

N2O Source Mt N2O yr-1 Gt C-eq yr-1

Cultivated soils 3.5 (1.8–5.3) 0.9 (0.5–1.4)

Biomass burning 0.5 (0.2–1) 0.1 (0.05–0.3)

Livestock (cattle and feed lots) 0.4 (0.2–0.5) 0.1 (0.05–0.13)

Natural tropical soils—wet forests 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)

N2O Source

Carbon Stocks Land-use change is often associated with

a change in carbon stocks.

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)

Carbon Stocks (Gt C)

Biome 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

Total 151.2 466 2011 2477

Land use managent

Vegetation can “sequester” or remove carbon dioxide from the atmosphere and store it for potentially long periods in above- and below-ground 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

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.

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

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.

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: , straw-incorporated 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, long-term food shortages and aggravation of societal problems could result.

Climate Reasons that affect the

Rice Growing1. 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.

. 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.

2. Stratospheric Ozone Depletion Effects on Rice---UV-B Radiation:

Climate Change— Rice Response to UV-B

Targets

Growth,Yield Morphology, Chemical matters

UV-B

Photosynthesis Carbon Allocation

Competition pest, Pathogen, Decomposition

Biodiversity

YieldBiogeochem Circling Endpoint

s

Ecosystem

Whole Plant

Tissue

Molecular

known less known

0

2

4

6

8

10

12

14

16

1 2 3 4

0 16 23 32

Effect of UV-B on Rice Yield

Seed dry weight (g)

Percent UV-B Enhancement

Cultivar ‘Lebonnet’

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.

0 1 2 3 4 5330

450

570

0

1000

2000

3000

4000

5000

6000

7000

8000

yiel

d (

kg/h

a)

Temperature change (K)

CO2 (ppm)

Interactive effects of CO2 and temperature

(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

GFDL GISS UKMO

Name Geophysical

Fluid Dynamics Laboratory

Goddard Institute of

Space Studies

United Kingdom

Meteorological Office

Base CO2 (ppm) 300 300 323

Temperature change ( C)

+4.0 +4.2 +5.2

Precipitation change (%)

8 11 15

General Circulation Models (GCMs)

GFDLGFDL

% change in regional rice productionpredicted by ORYZA1 and SIMRIW under

different GCM scenarios

GFDL GISS UKMO

ORYZA1 +6.5 -4.4 -5.6

SIMRIW +4.2 -10.4 -12.8

68 weather stations

(Matthews et al., 1995)

3 GCM scenarios

Predicted yield changes

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 UV-B 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.