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Transcript
THE INTRODUCTION
The earth is surrounded by atmosphere composed of many gases. These gases allow the sun’s
rays to penetrate to the earth’s surface while at the same time prevent much of the heat from escaping
back into space. The concern over global warming is based on the possibility than an enhanced
greenhouse effect is attributable to human activities that have increased the concentration of these gases in
the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) estimates that the increasing
concentrations of greenhouse gases (GHG) could raise the average global temperature by 1 by 2030 and 3
by 2100. The purpose of this report is to identify and qualify anthropogenic (human induced) sources of
atmospheric emissions of greenhouse gases (GHG) in order to determine possible solutions for reducing
emissions.. The gases that will be discussed are carbon dioxide (CO2), methane (CH4) and nitrous oxide
(N2O).
CANADA AND AGRICULTURE
Although Canada is the second largest country in the world, only 5% of her land is suited for
agriculture (about 46 million hectares). These agricultural lands represent about 293,000 farms. Widely
developed farming systems have developed in Canada. Canada is divided into ecozones, which represent
varying abiotic and biotic factors. Different climate conditions and soil types in this ecozones have
resulted in the development of a wide range of farming systems in Canada.
There are a number of changes that are expected to occur in Canada as a result of increased
levels of GHGs. The temperature in Canada is expected to increase, with the greatest changes on the
prairies. Canada is also expected to experience an increase in precipitation. The sea level will rising along
the Canadian coastlines. These changes will present new challenges for the agricultural community.
Canadian provinces have experienced periods of increased temperature and decreased
precipitation in the past. Between the years 1933 and 1937, precipitation fell 50%. Prairie wheat and corn
production fell by 32 and 50 percent respectively. Again in the late 1980s, Canada experienced a decline
in precipitation of 40% and a rise in temperature of 5 degrees C. Yields in grain and specialty crops fell
by 29 and 40 percent respectively. Livestock production also decreased during these periods due to the
drop in feed and pastureland. The direct dependence on climate makes the agricultural sector highly
sensitive to global warming. Increases in global temperature and greater variability in climatic conditions
will force farmers to adopt new management practices.
THE GREENHOUSE EFFECT AND GLOBAL WARMING
Gases in the atmosphere trap heat between the surface of the earth and the upper atmosphere.
This ability to trap heat is referred to as the Greenhouse effect. Carbon dioxide (CO2) is one of the most
important infrared absorbers. CO2 absorbed wavelengths ranging from 12.5 to 18.2 Mm, 11.8 to 9.1 Mm,
and 4.2 to 4.8 Mm. Other gases such as Methane (CH4), nitrous dioxide (N2O) and CFCs absorb radian
in the 7 and 12 Mm range. The concentration of these gases in the atmosphere determines how much heat
is trapped in the atmosphere.
CO2 is currently responsible for over 60% of the enhanced greenhouse effect. Current 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. CH4 from past emissions currently contributes 15-20% of the enhanced greenhouse
effect. N2O, CFC, and ozone contribute the remaining 20% of the greenhouse effect.
The earth’s climate is driven by a continuo flow of energy from the sun. This energy arrives
mainly in the form of visible light. Approximately 30% of this energy are reflected back into space, the
other 70% of energy pass through the atmosphere to warm the earth. The earth sends this energy back into
space in the form of infrared radiation. This energy is carried away from the earth’s surface by air currents
and clouds. Greenhouse gases in the atmosphere block infrared radiation from escaping directly from the
surface to space.
THE GREENHOUSE GAS INVENTORY
On a global scale agriculture ranks 3rd in its contributions to GHG emissions. There are a number
of important “greenhouse gases” (GHG). These gases include carbon dioxide (CO2), methane (CH4), and
nitrous oxide (N2O). Water vapor is also a GHG but humans do not affect this gas directly. Oxygen makes
up approximately 21 percent and nitrogen approximately 78 percent.
The main greenhouse gases (GHG) are water vapor, carbon dioxide (CO2), ozone, methane
(CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFC). Together these gases make up less than 1%
of the atmosphere. This is enough to produce a “natural greenhouse effect” that keeps the earth about 30
degrees warmer than it would otherwise be. Levels of all key greenhouse gases are rising as a direct effect
of human activity. The result is an “enhanced greenhouse effect”.
GLOBAL WARMING POTENTIAL
Each gas in the atmosphere has a different global warming potential (GWP). A global warming
potential (GWP) is the time integrated change in “radiative forces” due to the instantaneous release of 1
kg of a trace gas expressed relative to the radiative forces from the release of 1 kg of CO2. It represents a
relative measure of the warming effect that the emission of a radiative gas might have on the surface of
the troposphere. The GWP takes into account the radiative forcing due to incremental concentration
increases and the lifetime of the gas. CO2 is the most important GHG. Impact of a GHG is often converted
to CO2 equivalence. It is therefore possible to make carbon policies applicable to other GHGs.
The net direct GHG emissions can be calculated as the sum of various sources of CO2 (netting
out C absorbed by growing plants or livestock consumption of feed), plus methane emissions from
ruminants, N2O emissions from fertilizers (both converted to a C base using global warming potential),
and the net C flux from changes in land use.
CARBON DIOXIDE
Carbon dioxide is the most important GHG in Canada. It accounts for over 60% per cent of
infrared absorption due to all greenhouse gas emissions. The production and use of fossil fuels accounts
for almost 97 per cent of Canada’s total anthropogenic emissions of CO2. Three percent comes from
industrial processes such as cement and limestone production Carbon dioxide is one of the end products of
the combustion of organic materials. The current concentration of atmospheric CO2 is 357 parts per
million by volume (ppmv).
In 1990, Canada’s emission of CO2 from fossil fuel combustion was around 461 Mt or 125 Mt C.
This corresponds to about 2% of the global estimate of 6000 Mt C (Marland, 1992). On a per capita basis,
Canada is ranked third in the world for CO2 emissions. Combustion related emissions of CO2 are
considered relatively accurate. However, information on the net fluxes of carbon from agricultural
practices and other anthropogenically driven fluxes is scarce. Estimates of carbon from losses from
agriculture soils are not available.
Carbon dioxide from burning of fossil fuels is the largest single source of greenhouse gas
emissions from human activities. Deforestation is the second largest sources of carbon dioxide. The supply
and use of fossil fuels accounts for about 3/4 of mankind’s carbon dioxide emissions. Converting land to
agriculture practices can result in substantial losses of soil carbon and most soils currently under
cultivation in Canada have lost approximately 50% of their original carbon content. . Natural wetlands
should be preserved. Flooded soils of wetlands are very high in carbon with long retention times. Draining
wetlands causes rapid oxidation of soils and subsequent carbon losses
Freezing CO2 emissions at their current level would postpone CO2 doubling until 2100.
Emissions would have to fall by 30% of current levels to stabilize at doubled CO2 levels sometime in the
future. Climate models predict that the global average temperature will rise by about 2 C (3.6F) by the
year 2100 if current emission trends continue.
METHANE
Methane (CH4) is an important greenhouse gas. It plays a major role in controlling the
abundance of both tropospheric ozone (O3) which is an important greenhouse gas near the tropopause and
the hydroxyl (OH) radical, which controls the atmospheric lifetime of other gases of climatic importance
(IPCC, 1992). Methane can also be oxidized to form CO2. Globally, the major sinks are estimated about
460 MT CH4 per annum. This emission rate includes both anthropogenic (360 Mt) and natural (140 Mt)
sources. Landfills account for about 38% of total anthropogenic methane sources. Other sources include
upstream oil and gas operations (29%) and domesticated animals (27%). Emissions can be controlled
through the use of methane digesters and improved storage systems. Because CH4 is not directly
sequestered by biomass, it is difficult to quantify the proportion of emissions that should be considered
part of a closed cycle.
Methane’s (CH4) overall contribution to global warming is large. It is estimated to be twenty-one
times more effective at trapping heat in the atmosphere than CO2 over a 100-year period. The agricultural
sector accounted for approximately 30% of total emissions. Enteric fermentation in domestic livestock
accounted for the majority. Other agricultural activities include rice cultivation likely results in a
reduction of methane consumption by soil of about 30%.
Emission estimates of CH4 depend on many factors. From combustion sources, emissions depend
on the type of combustion device, the age of the device, operating temperature, fuel types, ambient
temperature, whether emission control devices have been installed. Globally, methane emissions could be
reduced anywhere from 25-80% using current technology (Cole, 1996)
Methane is the second most important greenhouse gas. Cattle, dairy cows, buffalo, goats, sheep,
camels, pigs and horses produce methane. Most livestock related methane emissions are produced by
“enteric fermentation” of food by bacteria and other microbes in the animals’ digestive tracts; another
source is the decomposition of animal manure. Livestock accounts for one quarter of the methane
emissions. Alternative feeds containing less cellulose could reduce CH4 production. Methane emissions
from livestock could be cut with new feed mixtures. Cattle and buffalo account for an estimated 80% of
annual global methane emissions from domestic livestock. Additives can increase the efficiency of animal
feed and boost animal growth rates, leading to a net decrease of 5-15% in methane emissions per unit of
beef produced. The rate of CH4 generation from enteric fermentation depends on the feed, the animal and
its health.
Rice cultivation also releases methane. “Wetland” or “paddy” rices farming produces roughly
one fifth to one-quarter of global methane emissions. Bacteria and other microorganisms in the soil of the
flooded rice paddy decompose organic matter and produce methane. Losses in wetlands (swamps and
marshes are estimated to contribute approximately 75% of CH4 emissions) could also reduce methane
production. Methane from wet rice cultivation can be reduced significantly through changes in irrigation
and fertilizer use. Recent experiments suggest that draining a field at specific time during the crop cycle
can reduce methane emissions by up to 50% without decreasing rice yields. Additional technical options
for reducing methane emissions are to add sodium sulfate or coated calcium carbide to the urea-based
fertilizers now in common use, or to replace urea altogether with ammonium sulfate as a source of
nitrogen for rice crops
NITROUS OXIDE
Nitrous Oxide (NO2) is another important absorbing trace gas that contributes to the greenhouse
effect. Nitrous oxide is a GHG that is produced naturally from a wide variety of biological sources in soil
and water. Although N2O emissions are lower than CO2 emissions, N2O are approximately 310 times
more powerful that CO2 at trapping heat in the atmosphere over a 100-year time horizon. On a molecule
per molecule basis, NO2 has a radioactive forcing of about 200 times that of CO2. The 1992 atmospheric
concentration of NO2 is about 310 ppbu (8% T over the pre-industrial are). The current rate of
accumulation of N2O in the atmosphere is about 3 to 4.5 Mt N.
The main human generated activities producing N2O are soil management practices, fertilizer
use and fossil fuel consumption. Emission estimates of N2O depend on many factors. From combustion
sources, emissions depend on the type of combustion device, the age of the device, operating temperature,
fuel types, ambient temperature, whether emission control devices have been installed. Soil management
practices such as irrigation, tillage or summerfallow can effect N2O fluxes to and from the soil. These
sources are highly variable; soil is a small sink for N2O during dry conditions and a large sink during wet
conditions. Other N2O emitting activities include the burning of agricultural crop residues and changes in
land use. 1990 sources of N2O for Canada have been estimated as follows: fuel consumption 52%,
industrial processes at 36%, fertilizer use at 12%.
Nitrous oxide emissions from agriculture result from fertilizing soils with mineral nitrogen and
manure, biological nitrogen fixation in crops and enhanced soil nitrogen mineralization. Humans produce
14.8 million tones of N2O/N each year. About 5.4 million tones of N2O originate from agriculture.
Liberation of N2O from soils is associated with the oxidation of mineral nitrogen when either organic or
inorganic nitrogen fertilizers are applied. Most of the nitrogen fertilizer is oxidized to nitrates before it is
taken up by plant growth. This oxidation process is known as nitrification. If soils are waterlogged or
poorly drained, nitrates can be reduced by facultative anaerobic bacteria to N2O which can be further
reduced to N2 before it is released to the atmosphere. This process is called denitrification. The amounts
of N2O formed depends on soil factors such as oxygen supply, water content, temperature, structure,
organic matter content and nitrate concentration. Estimates of total emissions of N2O from fertilizer
production in Canada range from 3.3 kt to 27.8 kt, the average being 10.7 kt. Nitrous Oxide is emitted
into the atmosphere from several sources including; oceans, freshwaters, fires, lightening and vegetation.
Fertilizer use increases nitrous oxide emissions. The nitrogen contained in many fertilizers
enhances the natural processes of nitrification and denitrification that are carried out by bacteria and other
microbes in the soil. These processes convert some nitrogen into nitrous oxide. The amount of N2O
emitted for each unit of nitrogen applied depends on the soil type and amount of fertilizer, soil conditions,
and climate. Nitrous oxide emissions from agriculture can be minimized with new fertilizers and
practices. Fertilizing soils with mineral nitrogen and with animal manure releases N2O into the
atmosphere.
Significant reductions in emission levels could be achieved by adopting management practices to
improve efficiency in usage. By increasing the efficiency with which crops use nitrogen, it is possible to
reduce the amount of nitrogen needed to produce a given amount of food. One approach to reduce nitrous
oxide is to match the timing and amount of nitrogen supply to crops specific demands. Another is to use
advanced fertilization techniques such as controlled release fertilizers and systems that deliver fertilizer to
the plants roots through its leaves rather than through the soil (where most nitrous oxide production
occurs). The fertilizer’s interaction with local soil and climate conditions can also be influenced by
optimizing tillage, irrigation, and drainage systems. In Canada, 92% of the ammonia fertilizer is used in
agriculture to sustain soil fertility and grow crops (Environment Canada, 1987). The use of ammonia can
increase the organic carbon content of soils and thereby act as a sink for CO2.
THE CARBON CYCLE
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. Oceans, soils and trees are considered sinks or reservoirs of carbon.
Since the industrial revolution, carbon sources or flows have risen, principally this is because of fossil fuel
combustion. The agricultural sector uses large amounts of fossil fuel in cropping operations. Management
of land resources can alter the balance of trace gas emissions and return the cycles to equalibrium.
Practices such as conservation of natural land to cropland, wetland drainage, or re-establishment of
grasslands or forests effect the GHG balance.
Atmospheric concentrations of carbon dioxide and other greenhouse gases can be lowered by
reducing emissions or by taking CO2 out of the atmosphere via photosynthesis and sequestering it in
different components of terrestrial, oceanic and freshwater aquatic ecosystems.
A sink is the storage facility for a greenhouse gas that is removed from the atmosphere. In Canada, farm
management practices, especially conservation tillage has reduced the amount of soil CO2 emissions.
The key to gaining international acceptance of C sequestration in agricultural soils is to have a confident
projection of the potential, nationally and internationally and having an agreed methodology for
determining verifiable changes in stock.
CLIMATE CHANGE AND AGRICULTURE
The relationship between climate and agriculture involves both mitigation and adaptation issues.
The mix of crops and livestock depends on climate and water availability. As climate warms farmers may
shift to crops and animals that are currently found in more southern regions. As soils become drier,
farmers may need to increase irrigation practices. Adapting to climate change may adversely affect the
environment. In areas with available soils, cultivation could extend into regions that currently support
native forests. The changing climate is also likely to alter the geographical extent and plant composition
of northern ecosystems. The agricultural potential for Canada is constrained by agroclimatic factors such
as heat accumulation, moisture availability and the length of the growing season. Any changes in the
earth’s climate will change these conditions.
Concern over GHG relates to their effect on weather pattern. Few industries are as vulnerable to
changes in climate as agriculture. At the global level, the rate of evapo-transportation is expected to
increase. Changes in these cycles will affect the agricultural sector. Predictions suggest more precipitation
with higher evaporation rates. This will reduce stored moisture during the growing season. The challenge
for agriculture is to develop sustainable farming techniques for these new weather conditions.
Impacts
of climate change on agriculture will vary from crop to crop, location to location, and system to system.
Adaptation of farming practices may be constrained by factors other than climate and crop genetic
capacity, including availability of suitable soils and adequate supplies of water. In addition to climate,
crop yields depend on air quality, soils moisture and nutrient content, farming practices (which are
continually evolving) and more climate change may affect agricultural yields indirectly through disease
and pests stimulated by warmer climate. Higher temperatures will cause increases in evaporation rates.
Higher temperatures could cause increases in the demand for irrigation of agricultural land. Increases in
precipitation could lead to leaching of nutrients from the soil. Changes to land use could include area
farmed, type of crop cultivated, planting location.
Some agricultural regions will be threatened by climate change, while others may benefit. The
impact on crop yields and productivity will vary considerably. Climate and agricultural zones are likely to
shift toward the poles. In the mid-latitude regions (45-65) present temperature zones could shift by 150550 km. Since each climate belt is optimal for a particular set of crops, such shifts in temperature could
strongly affect agricultural and livestock production. The productivity of rangelands and pastures would
also be affected. Grasslands support approximately 50% of the worlds’ livestock and are also grazed by
wildlife. Shifts in temperatures and precipitation may reshape the boundaries between grasslands, shrub
land, forest, and other ecosystems.
Forest plays an important role in the climate system. They are a major reservoir of carbon,
containing some 80% of all carbon stored in land vegetation, and almost 40% of the carbon residing in
soils. Large quantities of carbon may be emitted into the atmosphere during transitions from one forest
type to another because mortality releases carbon faster than growth absorbs it. Forests also directly affect
climate on the local, regional, and continental scales by influencing ground temperature, evapotranspiration, surface roughness, albedo, cloud formation and precipitation
Although climatologists suggest that drier soils will accompany changing climate there may be
some offsetting factors. In colder areas, such as Canada, warmer temperatures may lengthen the growing
season. In addition, higher levels of carbon dioxide may have a fertilizing effect, enabling plants to grow
more rapidly. Finally, higher levels of CO2 may increase the efficiency with which plants use water.
These benefits may offset the effects of dryer soils.
Future emissions are uncertain, and they have to be translated into future atmospheric
concentrations using models of the carbon cycle and atmospheric chemistry. Rising carbon dioxide levels
cause plants to grow faster (the “CO2-fertilization effect”) and absorb more carbon dioxide through
photosynthesis. CO2 fertilization, together with forest re-growth in northern countries, may be absorbing
up to 25% of the carbon dioxide currently produced by human activity human activity. Higher levels of
CO2 should stimulate photosynthesis in certain plants. In C3 plants, increased carbon dioxide tends to
suppress their photorespiration, making them more water efficient. C3 plants include species, such as
wheat, rice, barley, cassava, and potato. Experiments in doubling Co2 emissions increase yields by 30%.
The response of C4 plants would not be as dramatic. C4 crops include maize, sugar cane, sorghum and
millet. Total precipitation is predicted to increase. More rain and snow will mean wetter soil conditions in
high-latitude winters, but higher temperatures may mean dryer soils in summer. Local changes in soil
moisture are important for agriculture.
It is too early to predict the pattern of climate change in specific regions. A greater understanding
about physical processes such as soil erosion, nutrient cycles, hydrological processes, pests, and disease
before decisions can be made. A proper evaluation of the role of agriculture in climate change and its
contribution to emissions requires both the sources and sinks to be quantified The ability to adjust to the
effect of climate change will limit the rate of adaptability. Further research needs to be undertaken to
improve knowledge of the effects on crop yield and livestock for different regions of the world and for
different types of agricultural systems. Higher temperatures will affect production patterns. Plant growth
and health may benefit from fewer freezes and chills, but some may be damages by higher temperatures,
particularly if combined water shortages. Certain weeds may expand their range into higher-latitude
habitats. There is also some evidence that the pole ward expansion of insects and plant diseases will add
to the risk of crop loss.
Opportunities for reducing agricultural emissions include sequestering carbon into soils and
properly managing agricultural sources of greenhouse gases. Sequestration of soil carbon is enhanced
when the flux of carbon into soil increases and when soil disturbance is reduced. 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. These practices control emissions and provide other environmental benefits such as improved
soil and water quality.
SOIL QUALITY
Levels of organic matter in Canada’s soils have declined with estimates ranging from 15-50%
since cultivation began. Farming practices directly affect the level of organic material in the soil. Crop
production practices must change to ensure soil productivity continues. Producers need to change the way
the farm. Conservation farming is significantly affected by moisture level in soil. This level depends on
moisture accumulated through winter snowfall and rainfall prior to and at the time of seeding. Lack of
precipitation will affect crop yields. Soil organic matter content is closely linked with soil quality and soil
productivity. The rate of decomposition is controlled by soil conditions, composition of the organic
material, placement of material in the soil profile and the degree of physical protection.
World soils constitute a pool of 1500 to 2000 Pg (1Pg=petagram=1 billion metric ton). Soil
organic carbon (SOC) refers to the carbon content in soil to a depth of 1 meter. The carbon pool in
Canada is approximately 190 Pg. The historic loss of SOC, is estimated at 1Pg. Much of the carbon loss
occurred during the first decade of cultivation. Most soils in Canada today are almost neutral with respect
to emissions. Farming practices could be adopted to recover these losses. Although there is some evidence
that agricultural soils can become a net sink for CO2, the level of this potential sink in uncertain. Once
soils have reached some equalibrium state, this value can not 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
Soil begins to change as soon as it is “broken” and converted from a natural state to one suitable
for agriculture. Up to 40% of soil carbon is lost when previously untilled soils are opened up for
cultivation. Farming introduces a new system of plant growth that changes the balance of water in the
soil, organic material, and nutrient composition exposing it to wind and water erosion. Some tillage and
cropping methods break down the structure of the soil. Other practices such as liming acid soils, draining
water logged soils and removing stones may improve soils from their natural state. As soil health declines,
more fertilizer and pesticides are needed to maintain acceptable crop production. Poor soils are less able to
hold and use these chemicals, which are often found in surface water or under ground water supplies.
Unhealthy soils are less effective in the role of gas exchange and maintaining air quality.
Increasing soil organic carbon in recognized as a means to increase agricultural production.
Principle processes of C sequestration in soil include humification of organic materials, aggregation by
formation of organic complexes, deep placement of organic matter beneath the plow zone, deep rooting
and calcification. Leading causes of decline in soil organic matter content include erosion, compaction,
and decline in soil structure, mineralization or oxidation of humic substances. The soil degradation
processes are set in motion by anthropogenic activities including plowing, biomass burning, draining
wetlands, grazing and mining of soil fertility by no-input or low-input subsistence agricultural practices.
The objective of soil management practices is to enhance soil productivity through improved soil organic
content improving agricultural productivity.
FARM MANAGEMENT PRACTICES
Agriculture and forestry management practices can effect the global carbon cycle. High latitude
continental areas can store carbon for longer periods. The use of good management practice can sequester
carbon and in some cases offset any emissions caused by the production of fertilizers. However, not using
fertilizers when required may be environmentally harmful because it reduces the production of protective
biomass. Forest ecosystems account for approximately 50% (100 Mt C) of the annual exchange of CO2
with the atmosphere. Carbon stores in forests are attributed as follows; approximately 1500 Mt C for soils
and approximately 650 Mt C for standing biomass. Canada has a total land area of 997 M ha. Forrest
represents 453 M ha of this area (82% boreal forest, 18% Temperate Zone)
An increase in conservation farming and abandonment of marginal land would improve soil
conservation, soil moisture and habitat for animals and wildlife. Agriculture can help reduce atmosphere
CO2 by storing more carbon in soil through alternative practices and eliminating excessive use of nitrogen
fertilizer. The agricultural sector must develop and utilize new management techniques for enhancing soil
carbon by increasing the quality and quantity of carbon residues and by changing the type and intensity of
tillage. Growing native plants or adopting new varieties of grains more resistant to higher temperature
and drought conditions may improve yields.
Conservation tillage refers to any tillage and planting system which maintains at least 30% soil
surface covered by residue after planting. A new crop is planted directly into the stubble of the previous
crop with minimum soil disturbance. No-till can significantly increase carbon sequestration in soil.
Greenhouse gas emissions are reduced through improved yields. Erosion is controlled through residue
management and post-emergent herbicide applications. Greenhouse gas emissions are further reduced
through decreased fossil fuel use. Other benefits of conservation tillage include improved water quality,
decreased run off, less erosion and reduced particulate emissions. In addition to conservation tillage and
erosion control, there are several other practices that will maintain and restore carbon in depleted soils.
Reducing summerfallow and switching to continuos cropping helps increase soil carbon content. Carbon
sequestration is increased in sold with low fertility. Adding nutrients such as nitrogen, phosphorous and
potassium at appropriate times and liming of acid soils helps maintain and improve soil fertility.
Mulching or using plant residues in the soil helps maintain cooler soil temperatures and keeps the topsoil
wetter. This slows decomposition and preserves soil carbon.
New pharmaceuticals are being developed for ruminants that promote protein gain at the expense
of fat. This could reduce methane emissions up to 20% (cast, 1992).
There are approximately 19.4 million hectares of grassland in Canada used for seasonal grazing.
This land is often overlooked, as an opportunity for carbon sequestration. Over-grazing and undergrazing prevent soils from maximizing carbon sequestration. Agricultural management land techniques
provide economical and environmental benefits to farmers compared to conventional techniques. There
are additional opportunities from improving nutrition to manure management in feedlots.
AVAILABLE TECHNOLOGY
Technological progress is the elements of a crop farming system that offer new and different
ways to crop effectively. The Global Positioning System (GPS) is a recent technological advancement that
could change the way farming is operated to ensure reductions in agricultural greenhouse emissions. The
Global Positioning System of satellites 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). Access to such a system would enable farmers to properly utilize their farming
inputs. Such a system if developed properly would be economically appealing to a farmer reducing both
input costs and time spend on unnecessary application runs. This system would also offer environmental
benefits. Fossil fuel usage would decline in direct proportion to reduced application runs. This would
correspond to less CO2 emissions. Fertilizer and herbicide application could be applied only on land
requiring those particular inputs. Less chemical applications would mean reductions in CO2 and N2O.
Optimal livestock/ land ratios could be identified to ensure maximum plant cover, soil organic matter, and
animal productivity.
A standard protocol for sampling soils for carbon measurement was developed and tested on the
prairies (Ellert & Janzen 1996). This model can be used as a proxy for measuring carbon change in every
farmer’s field. This sampling system will be completed by the year 2000. Farmers will be able to use this
model to verify their changed in carbon stock for emission trading purposes.
The lack of understanding of soil carbon benefits and achievements to date, outside the farming
community is a barrier for further development. Support is needed to ensure continued adoption of these
practices. Uncertainties related to economic and environmental benefits for the farmer will only slow this
progress. There needs to be a mechanism in Canada that will disseminate information and provide
technical support on carbon sequestering opportunities. The advancement of technology has introduced
computers into many agricultural homes. Farmers could easily access information if it were available.
RENEWABLE ENERGY
The greatest potential for mitigating carbon dioxide lies in increasing the amount and variety of
plant biomass used as a substitute for fossil energy. Unlike fossil fuels, crops used for bio-fuels remove as
much carbon dioxide from the atmosphere as they release during combustion. It is estimated, that carbon
emissions could be reduced, by approximately 0.1 Mt per year, by the year 2000, if 10% of all Canadians
used gasoline containing 10% ethanol made from Canadian grain.
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. It is more
appropriate to treat fossil fuel sources and bio-related sources and sinks separately and examine the
anthropogenically driven changes in these terms.
SUSTAINABLE DEVELOPMENT
.
In a zero tillage or direct seeding system. A producer requires a seed drill able to penetrate the
ground and place the seed at the proper depth. The differences between conventional and zero tillage
systems are most apparent in the area of weed control. There are many factors a producer can use to
control weeds including time of seeding, variety selection of crop, optimal placement of seed and
fertilizer, field border sanitation
Conservation practices include increased residue amounts, increased vegetable cover and wind
breaks. Practices such as summerfallow, winter cover, length of rotation, direct seeding, permanent cover,
stubble burning affects the health of soil resources. Conserving and planting natural grasses may increase
carbon storage by increasing overall carbon storage by increasing overall 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
Livestock and the land are linked. Without healthy soils for grazing and forage production, the
Canadian livestock industry can not keep up with the increasing demand. Farmers need to find new ways
to deal with animal wastes. Livestock manure is very beneficial when applied at the appropriate rate, but
intensive operations do not have enough land to disperse manure properly. Problems arise in the form of
strong odors to the release of volatile compounds into the atmosphere. Contaminated soils can damage the
health of livestock. Compounding reduces the weight and bulk of manure so that it can be more
economically transported and applied.
The anaerobic microbial fermentation of carbohydrates in the digestive system of animals
produces CH4. CH4 production rates in dairy cattle depend on diet, live weight and milk production,
energy intake, enteric ecology, energy expenditure of the animal, quantity and quality of the feed, body
weight, age and exercise of the animal. It is estimated that about 5-9% of gross energy intake of ruminants
is lost to CH4 production (Crutzen, 1986). The potential for CH4 production is directly related to the
amount of volatile solids present in animal waste.
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. There is potentially significant
carbon sequestration gain opportunities for managed livestock grazing. Speculation about offsetting
methane emissions is a real barrier to promotion of this opportunity. Reduction in the numbers of animals,
which is often suggested as a policy option, does lowers methane emissions. However, this option may not
be available given growing world demands.
AGRICULTURE AND FOOD SECURITY
Studies suggest that global agricultural production could be maintained for the next 100 years
Regional effects of global warming will vary widely. Some countries will experience reduced output. The
negative effects of climate change could be limited by changing in crops and crop varieties, improving
water-management and irrigation systems, adapting planting schedules and tillage practices, and better
watershed management and land-use planning.
GLOBAL PROGRESS AND CANADA’S COMMITMENT
Environment Canada estimates that the country is responsible for 2% of global emissions. In the
1992 United Nations Framework Convention on Climate Change, Canada and other developed countries
committed to put in place policies and measures with the aim of returning greenhouse emissions to their
1990 levels by the year 2000. To implement these commitments Federal and Provincial governments have
developed Canada’s National Action Program on Climate Change.
At the first meeting of the conference of the parties to the framework Convention in 1995, the
parties agreed that the initial aim of the convention was inadequate. They agreed that new commitments
should be reached by the third Conference of the Parties in Kyoto. In December 1997, negotiations were
concluded on a new agreement. Canada has agreed to a target 6% below 1990 levels by 2008-2012. This
target will be difficult to achieve. Before Canada ratifies the Kyoto Protocol, First Ministers directed that a
process be established to engage governments and stakeholders to access the socio-economic implications
of actions required to meet the Kyoto Protocol.
Canada is developing a national implementation strategy in response to the Kyoto Agreement.
This strategy will require coordination among several levels of government. First Ministers will provide
guidance on the climate change issue. Federal, Provincial, and territorial Energy and Environmental
Ministers will measure Canada’s response to change. Other Federal, Provincial and Territorial Councils,
including Transportation and Agriculture Ministers will deal with actions related to their specific
mandate.
The National Air Issues Coordinating Mechanism (NAICC) will facilitate linkages among “Issue
Tables”. These are committees assigned to investigate particular issues related to greenhouse gases. A
table is a manageable group of stakeholders and governments assigned to particular issues. Each table will
prepare a report, which will be presented to the NAICC. The federal government hopes that by providing
opportunities for non-government stakeholders to participate in these talks, solutions will be found that
are sensitive to all involved. A number of tables have already been identified including modeling and
analysis, transportation, international emission trading, technology, sinks, credits for early action, and
public outreach. Extra tables will be assigned when issues are identified.
The protocol must be ratified before it is binding. The protocol commits developed countries to
specific emission reductions, but sets no binding requirements for developing countries who already enjoy
a competitive edge from lower labor and production costs. This could result in a significant trading
disadvantage for farmers in a world of free trade.
CONTROL MEASURES
There have been a number of control measures suggested to reduce agricultural related emissions.
These include; Increased 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.
The impact of the Protocol on food and agriculture industry is enormous. Policy makers must be
careful with binding legislation. Limiting energy use will drive up the cost of gasoline, electricity, food
manufacturing and transportation. Regulatory proposals such as new taxes on fossil fuels will cause
hardships on farmers. Restrictions on production amounts of some crops and livestock as well as
prescribed changes in cultivation practices are also being discussed. Mandatory operational procedures
could jeopardize integrated pest management programs designed to reduce pesticides through tillage and
crop rotations.
A real barrier to adoption of many new techniques is capital investment. First is the initial cost
for new farmers to acquire land and secondly money to purchase new equipment needed to achieve the
carbon sequestering opportunities. A second major barrier for the farmer is the fear of change. Fear that
carbon sequestering practices will become regulated requirements. Farmers need flexibility to adjust their
management for the annual fluctuations in weather and commodity prices.
POLICY OPTIONS
The instruments for achieving environmental goals can be classified into either command/control
or incentive based mechanisms. Command and control instruments include policy that applies restrictions
on levels. Policies that have been suggested to date are concerned with controlling or reducing emissions
as opposed to policies focused on increases in absorption rates. These options need to be considered.
Government and agribusiness must support research into crops more suited to the changing climate.
Governments must determine region vulnerability. New knowledge of ecosystems and effects of land
management practices are needed for new soil management systems. No till and conservation tillage
production systems need to be developed to deal with specific problems such as weed control.
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. Micro-life in soil must be constrained in soil
structure. Bacteria and fungi needs to be identified that will improve soil mineral nutrition, while remain
drought and disease resistant in host crops. Time and money is required for researchers to develop a better
understanding of natural crop and soil relationships to find out which rotation and techniques work best.
Time is required for scientists to develop alternative strategies to recycle residue nutrients and reduce the
depletion of carbon and nitrogen reserves. Indicators are needed to monitor effects of agricultural policies
on soil fertility, including responses to fertilizer inputs. In regions were forest clearance, forest
degradation and storage of wood products are important issues. Indicators are needed to monitor changes
and to assess the effects of them on policy changes and management measures.
Agriculture accounts for 20% of the human-enhanced greenhouse effect. Intensive agricultural
practices such as livestock rearing, wet rice cultivation, and fertilizer use emit 50% of human related
methane and 70% of our nitrous oxide. The carbon stored in trees, vegetation, soils, and durable wood
products can be maximized through “storage management”. Agricultural soils are currently a net source
of carbon dioxide. Properly designed management techniques could make them a net sink. As much as
400-800 million tons of carbon dioxide could be taken up by agricultural soils every year through
improved management practices designed to increase agricultural productivity. Farmers can alter their
management practices by adapting new seed varieties and employment of alternative cultivation methods.
Soil can only store a finite amount of carbon so increased carbon sequestration is possible only for a
limited time. Reduced carbon emissions through decreased fossil fuel use can be maintained indefinitely.
A 10-50% decrease in the use of fossil fuel energy by agriculture in industrialized countries may reduce
net carbon emissions by 0.001-0.005 Gt. annually.
Many studies present opportunities that exist for reducing greenhouse emissions, however many
do not take into account the adoption rate of a technique by a farmer. Convincing farmers and ranchers to
adopt the available techniques that encourage carbon sequestration may be difficult. In Saskatchewan 20%
of farmers have already adopted no-till farming. The rate of adoption for the past four years was 60,000 to
70,000 hectares per year. This rate could continue. Adoption of managed grazing and pasture fertilization
is still in its infancy.