Download • The earth is surrounded by atmosphere composed of many gases

THE INTRODUCTION
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The earth is surrounded by atmosphere composed of many gases.
The sun’s rays penetrate through the atmosphere to the earth’s surface.
Gases in the atmosphere trap heat that would otherwise escape into space.
The “natural greenhouse effect” increases the earth temperature by 30 C.
Levels of all key greenhouse gases are rising due to human activity.
The result is an “enhanced greenhouse effect”.
THE GREENHOUSE EFFECT
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The earth’s climate is driven by a continuous flow of energy from the sun.
This energy arrives in the form of visible light.
Approximately 30% of energy is reflected back into space.
The other 70% of energy pass through the atmosphere to warm the earth.
The earth sends this energy back to space in the form of infrared radiation.
Energy is carried away from the earth’s surface by air currents and clouds.
GHG in the atmosphere block infrared radiation from escaping to space.
THE GREENHOUSE GAS INVENTORY
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Agriculture ranks 3rd in its contributions to GHG emissions.
The main greenhouse gases (GHG) are water vapor, carbon dioxide (CO2), ozone, methane
(CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFC).
The atmosphere is composed of 21% oxygen and 78% nitrogen.
The GHG and other trace gases account for the remaining 1 percent.
Agricultural activities increase concentrations of CO2, CH4, and N2O.
GLOBAL WARMING POTENTIAL
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Each gas has a different global warming potential (GWP).
GWP represents a relative measure of the warming effect of each gas.
CO2 is the most important GHG.
The impact of a GHG is often converted to CO2 equivalence.
Equivalencies enable carbon policies to be applied to other GHG.
Freezing CO2 emissions at their current level would postpone CO2 doubling until 2100.
Emissions would have to fall by 30% to stabilize at doubled CO2 levels in the future.
CARBON DIOXIDE
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On a per capita basis, Canada ranked 3rd in CO2 emissions.
CO2 currently causes over 60% of the enhanced greenhouse effect.
Annual emissions amount to over 7 billion tons of carbon.
Estimates from Environment Canada’s National Greenhouse Gas Emissions Inventory
indicate that agricultural practices caused approximately 39.2 million tons of CO2.
97% of anthropogenic emissions from CO2 are attributed to fossil fuel.
Flooded soils of wetland are high in Carbon (C) with long retention times.
Draining wetland causes rapid oxidization of soil and subsequent C losses
High latitude continental areas can store carbon for longer periods.
METHANE
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Methane (CH4) is an important greenhouse gas.
CH4 from past emissions currently contributes 15-20% of the enhanced greenhouse effect.
It is 21 times more effective at trapping heat than CO2.
It indirectly determines the atmospheric lifetime of other GHG.
The agricultural sector was responsible for about 30% of CH4 emissions.
Most livestock related CH4 emissions are produced by “enteric fermentation” of food by
bacteria and other microbes in the animals’ digestive tracts.
The other main source of CH4 is the decomposition of animal manure.
Emissions can be controlled through methane digesters and improved storage systems.
Changes in irrigation and fertilizer use can reduce CH4 emissions from wet rice cultivation.
Globally CH4 emissions could be reduced anywhere from 25-80% using current technology
NITROUS OXIDE
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Nitrous oxide (N2O) is produced naturally from biological sources in soil and water.
N2O are approximately 310 times as effective as CO2 in trapping heat.
N2O, CFC, and ozone contribute the remaining 20% of the greenhouse effect.
Soil management practices, fertilizer use and fossil fuel consumption produce N2O.
Practices such as irrigation, tillage or summerfallow can effect N2O fluxes in the soil.
Soil is a small sink for N2O during dry conditions and a large sink during wet conditions.
The amounts of N2O formed depends on soil factors such as oxygen supply, water content,
temperature, structure, organic matter content and nitrate concentration.
Matching the timing and amount of nitrogen supply to crop specific demands will reduce
N2O.
Advanced fertilization techniques such as controlled release fertilizers that deliver fertilizer to
the plants roots through its leaves rather than through the soil will reduce N2O.
THE CARBON CYCLE
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The global carbon cycle is made up of flows and reservoirs.
When carbon is emitted into the atmosphere, it is a flow or a source.
A sink is the storage facility for a GHG removed from the atmosphere.
Oceans, soils and trees are considered sinks or reservoirs of carbon.
Carbon sources or flows have risen because of fossil fuel combustion.
Conversion of cropland, wetland drainage, or re-establishment of grasslands and forests
effect GHG.
Taking CO2 out of the atmosphere via photosynthesis and sequestering it in different
components of terrestrial, oceanic and freshwater aquatic ecosystems will reduce GHG.
CANADA AND AGRICULTURAL
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Canada is the second largest country in the world
5% of the land (46 million hectares) in Canada is suited for agriculture
Agricultural land represents 293,000 farms
Varying climatic conditions and soil types result in diverse farming systems
Saskatchewan’s experiences demonstrate the vulnerability of agriculture to global warming.
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Between 1933 and 1937 precipitation fell 50%
Prairie Wheat and Corn Production fell by 32 and 50 percent respectively
In the late 1980s precipitation fell 40% and temperatures increased 5 C
Yields of grain and specialty crops fell by 29% and 40% respectively
Livestock production decreased due to decline in feed and pastureland
CLIMATE CHANGE AND AGRICULTURE
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Impacts of climate change will vary between crops, location, and system.
Predictions suggest increased temperatures with the largest effects felt on the prairies.
Each climate belt is optimal for a particular set of crops.
Farming may be affected indirectly through disease and pests stimulated by warmer climate.
Certain weeds may expand their range into higher-latitude habitats.
Predictions suggest more precipitation with higher evaporation rates.
Increases in precipitation could lead to leaching of nutrients from the soil.
The rate of evapo-transportation is expected to increase reducing moisture during growing
seasons.
As soils become drier, farmers may need to increase irrigation practices
Climate change may alter the geographical extent and plant composition of ecosystems.
Cultivation could extend into regions that currently support native forests.
Climate and agricultural zones are likely to shift toward the poles.
In the mid-latitude regions (45-65) present temperature zones could shift by 150-550 km.
The boundaries between grasslands, shrub land, forest, and other ecosystems may change.
Adaptation of farming practices may be constrained by the availability of suitable soils.
Warmer temperatures may lengthen the growing season.
Higher levels of carbon dioxide may have a fertilizing effect, enhancing plant growth.
Higher levels of CO2 may increase the efficiency with which plants use water.
SOIL QUALITY
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Leading causes of decline in soil organic matter content include erosion, compaction, and
decline in soil structure, mineralization or oxidation of humid substances.
Unhealthy soils require more fertilizer and pesticides.
Unhealthy soils are less effective in the role of gas exchange and maintaining air quality.
Crop production practices must change to ensure soil productivity.
Most soils in Canada today are neutral with respect to emissions
Farming practices could be adopted to recover carbon losses
Once soils reach an equilibrium state, the value cannot be exceeded.
PHOTOSYNTHESIS
Photosynthesis is the process by which plants take carbon dioxide (CO2) from the
atmosphere and water (H2O) from the soil. With the use of the sun’s energy (light energy), the
plant produces 6 carbon sugars, which it uses for food, and gives off the by-product oxygen (O2)
back into the atmosphere.
The equation for photosynthesis is:
Light energy
6CO2 + 6 H2O
C6H12O6 + 6O2
The ‘food’ is stored in plant material: the root system and the foliage. Plant material is made up
of water (70%), organic matter (27%), and minerals (3%). Organic matter is made up mostly of
carbon and nitrogen and are returned to the soil during senescence and stored. The amount of
organic matter returned to the soil depends on if and how much of the plant is harvested
RESTORING CARBON IN DEPLETED SOILS
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The soil degradation processes are set in motion by plowing, biomass burning, draining
wetlands, grazing and mining of soil fertility by no-input or low-input subsistence agricultural
practices.
Farming introduces a new system of plant growth into a region.
This affects the balance of water, organic material and nutrients in the soil.
Carbon sequestration includes humification of organic materials, aggregation by formation of
organic complexes, placement of organic matter beneath the plow zone, deep rooting and
calcification.
Practices such as liming acid soils, draining water logged soils and removing stones may
improve soils from their natural state.
FARM MANAGEMENT PRACTICES
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Alternative farming practices include: increasing crop yields, reducing use of fossil fuels,
improving manure handling and storage, enhancing efficiency of nitrogen fertilizer, and
improving feeding technology for ruminant livestock.
Practices such as summerfallow, winter cover, length of rotation, direct seeding, permanent
cover, stubble burning affects the health of soil.
Conservation tillage refers to any tillage and planting system which maintains at least 30%
soil surface covered by residue after planting.
Benefits of conservation tillage include improved water quality, decreased run off, less
erosion and reduced particulate emissions.
Timing of nutrient applications and liming of acid soils helps maintain and improve soil
fertility.
Mulching helps maintain cooler soil temperatures preserving carbon and helps topsoil hold
moisture.
Differences between conventional and zero tillage are most apparent in weed control.
Weeds can be controlled by timing seeding, selection of crop, optimal placement of seed
and fertilizer, and field border sanitation.
Conserving and planting natural grasses may increase carbon storage by increasing
vegetation cover.
Native grasses are very effective at building up organic matter in soil.
They are also better adapted to surviving in the weather conditions in the long run.
Integrated pest management uses a combination of selected pesticides, insect population
surveys, cultural control methods, biological control and modification of farming practices.
DOMESTIC ANIMALS
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The livestock industry requires healthy soils for grazing and forage production.
There are approximately 19.4 million hectares of grassland used for seasonal grazing.
This land is often overlooked, as an opportunity for carbon sequestration.
Over-grazing and under-grazing prevent soils from maximizing carbon sequestration.
There is significant carbon sequestration gain opportunities for managed livestock grazing.
Livestock manure is very beneficial when applied at the appropriate rate.
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Intensive operations do not have enough land to disperse manure properly.
A combination of soil management practices, animal management practices and sustainable
agricultural practices and managing herd size to match productivity of rangelands may
increase plant cover and soil organic matter thereby improving animal productivity.
AVAILABLE TECHNOLOGY
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The Global Positioning System (GPS) could change farm management
This system is a set of satellites used for mapping the earth.
Some of the uses for GPS for agriculture include mapping (yield, fertility, soil type, moisture
content, and weed infestations) varying inputs (fertilizer, seed density, changing seed
varieties and chemicals) and guidance (seeding and spraying).
Fertilizer and herbicide could be applied only where needed thus reducing CO2 and N2O .
Fossil fuel usage would decline in direct proportion to reduced application runs. This would
correspond to less CO2 emissions.
Access to such a system would enable farmers to properly utilize their farming inputs.
Agricultural management systems will change farming operations.
Optimal livestock/ land ratios can be identified to ensure maximum plant cover, soil organic
matter, and animal productivity.
A standard protocol for carbon measurement in soils has been developed.
This system of measurement will allow farmers to trade carbon credits
The lack of understanding of soil carbon benefits is a barrier for further development.
Support is needed to ensure continued adoption of conservation practices.
RENEWABLE ENERGY
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The greatest potential for mitigating CO2 lies in the use of plant biomass for energy
Crops used for bio-fuels remove equivalent amounts of CO2 from the atmosphere as they
release during combustion.
Biomass currently contributes about 7% to Canada’s energy needs.
Bio-related sources have a sink term, whereas fossil sources do not.
The magnitude of this sink term is directly related to the size of the source term.
Bio related emissions would occur even in the absence of human intervention.
POLICY OPTIONS
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Policy suggestions for reducing emissions include; fuel economy requirements, reduction or
the phase out of diesel fuel, limitations on production per acre for some crops, requirements
for plowless soil preparation, mandatory fallowing of cropland, limits and restrictions on
timber harvesting, and restrictions on processing, manufacturing and transportation of food
products.
• Mandatory operational procedures could jeopardize integrated management programs.
• Farmers need flexibility in their operations for annual fluctuations in weather and commodity
prices.
• A real barrier to adoption of many new techniques is capital investment.
• Government and agribusiness must support research into alternative farming practices.
• Knowledge of ecosystems and the effects of land management practices are required.
• Researchers must look at ways for farmers to take advantage of the biological processes
within the soil and become less dependent on off-farm inputs.
A mechanism is needed to disseminate information and provide technical support to farmers on
carbon sequestering opportunities.