At the first World Summit on Sustainable Development, held in Rio de Janeiro in 1990, world leaders agreed that there was compelling evidence of the link between greenhouse gas (GHG) concentrations in the atmosphere and global change. Negotiations aimed at an international agreement to reduce greenhouse gas (GHG) emissions began with the United Nations Framework Convention on Climate Change (UNFCCC), which was signed by 180 countries in 1992. The goal of the UNFCCC is to reduce global GHG emissions to 1990 levels and to continue negotiations on further GHG reductions. At the third meeting of the Conference of the Parties (COP3) to the UNFCCC in Kyoto Japan in 1997, the Kyoto Protocol was signed. The Kyoto Protocol set out the basic framework for an international strategy to achieve global GHG reductions of 5% below 1990 over the first commitment period - 2008 to 2012. Canada’s emission reduction target under the Kyoto Protocol is 6% below 1990 emissions levels.

Negotiations to establish the detailed rules governing implementation of the Kyoto Protocol continued until the Marrakesh Accords were adopted at COP7 in 2001. At the conclusion of COP7, countries agreed that the Marrakesh Accords contained enough detailed legal text outlining the rules of the Kyoto Protocol and its implementation that Parties could begin the process of domestic ratification. The Kyoto Protocol will become international law when it is ratified by 55 countries representing at least 55% of the emissions covered under the Protocol. The withdrawal of the United States, which represents 25% of the world’s emissions, from the Protocol, means that Russia must ratify for the Protocol to come into force.

The flexibility mechanisms in the Protocol make it unique among international environmental agreements. The flexibility mechanisms will allow the creation of a market for trading of GHG emissions reductions and removals. In addition to emission trading, the Clean Development Mechanism will allow developed countries with targets to undertake GHG mitigation projects in developing countries – the developed country gets the emission reduction and the developing country gets access to cleaner energy technology. The Joint Implementation agreement will allow emission reduction projects to be undertaken between two developed countries, in which the host country gets the mitigation technology and in the investing country gets the GHG reduction.

Agriculture accounts for about 10% of Canadian GHG emissions. Large industrial emitters, like the energy, electric utilities and manufacturing account for about half of Canada’s emissions.

Emissions of GHG are increasing. Under a business-as-usual (BAU) scenario, the GHG Analysis and Modeling Group (AMG) estimates that emissions will rise from about 600 million tonnes (Mt) CO₂e in 1990 to about 810 Mt CO₂e in the first commitment period (2008-2012). Canada’s Kyoto target is estimated to be 570 Mt, so if emissions continue to rise at the BAU rate we will have to reduce emissions by about 240 Mt per year, or 33%, in each year of the commitment period.

Under the UNFCCC, Canada submits an annual inventory of its GHG emissions, including emissions from agriculture. Sources that must be included in the national inventory are emissions from enteric fermentation, mainly methane from cattle, methane and nitrous oxide from manure management and storage, agriculture soil emissions, mainly nitrous oxide from fertilizer and carbon dioxide from soil organic matter, and nitrous oxide emissions from the burning of crop residues. Emissions associated with rice production and burning of savannas are not applicable in Canada.

Unlike most other sectors of the Canadian economy, where carbon dioxide is the major GHG, in agriculture nitrous oxide and methane are the major gases. Accounting for GHG is done relative to carbon dioxide, which is assigned a 100-year warming potential of one. The warming potential of nitrous oxide is 310 times and methane is 21 times greater than carbon dioxide. Very small increases in emissions of those gases can therefore have a significant impact on the agriculture emission inventory.

Nitrous oxide and methane emissions from primary agriculture production have been increasing since 1990, mainly as a result of increased N fertilizer use and expansion in the livestock herd. Over the same period, carbon dioxide emissions have been declining, and it is estimates that Canadian agricultural soils are now a net sink for carbon dioxide. The adoption of direct seeding and low-soil-disturbance crop production practices and reduced frequency of summerfallow account for most of the emission reduction.

Inputs to the carbon cycle of the agro-ecosystem are solar energy from the sun and carbon dioxide. Output from the system is the organic carbon in the harvested crop. Assume that 6.3 t C/ha are fixed in the plant through photosynthesis and 2 t C/ha are respired (released from the plant), leaving 4.3 t organic C/ha in the crop biomass. If 1.3 t c/ha are harvested and exported that leaves 3 t C/ha in the crop residues. When the crop residues are added to the soil they are decomposed by soil microorganisms and some of the decomposed organic matter is released as carbon dioxide. The soil is sequestering carbon if the amount of carbon leaving the soil as carbon dioxide is less than 3 t C/ha.

The soil system is losing carbon (a source of carbon dioxide) if more than 3 t C/ha is lost from the added residues. Whether a soil is a source or a sink depends on its history and management.

Canadian agriculture is a comparatively efficient production system, and it is difficult to identify "easy" emission reductions. Managing N fertilizer and manure more efficiently could reduce nitrous oxide emissions, and better balancing of protein in feed with animal requirements could reduce nitrous oxide from manure, but it is difficult to find GHG emission reduction strategies that do not also reduce productivity. For the first commitment period, therefore, sinks in agricultural soils are the most important mitigation option for the sector. The adoption of sink-enhancing practices has been increasing since 1990, not because of their sink potential but because of the other environmental and economic benefits they offer. The sink capacity of agricultural soils is finite so in the longer-term, emission reduction technologies will have to be developed for agriculture, but over the next decades sinks offer 90% of the sectors mitigation potential.

The sink potential of the agricultural system was estimated using AAFC’s Canadian Economic and Emissions Model for Agriculture (CEEMA). The first analyses were based on 1991 and 1996 census of agriculture data on zero tillage and summerfallow frequency. For the BAU scenario, adoption rates were projected to 2010 along a relatively conservative trend line based on 1991 to 1996 adoption rates. Under that scenario, it was estimated that Canadian agricultural soils could sequester 4.2 Mt of carbon dioxide per year. A medium adoption scenario was also tested to estimate the sink potential if adoption rates could be increased above BAU. The table shows that if zero tillage could be increased to about 25% on the prairies, Canadian soils could sequester an additional 3.1 Mt of carbon dioxide per year. Further carbon dioxide removals could be achieved through above BAU reductions in summerfallow acreage, and above BAU increases in permanent cover crops, improved management of grazing land and agro-forestry.

The release of the 2001 census of agriculture data indicated that by 2001 Canadian producers had already exceeded the adoption rates of zero tillage and reduced summerfallow that had been projected to 2008. The scenarios were re-run using trend lines developed from the 2001 census. It is now estimated that Canadian agriculture soils could remove about 10 Mt of carbon dioxide per year in the commitment period under BAU. Further adoption of sink-enhancing practices at low, medium and high rates could removal additional carbon dioxide (about 5 Mt at low rates to about 17 Mt at high rates).

The chart shows the important role of sinks to GHG mitigation in agriculture. Modeled estimates indicate that emissions will increase from about 60 Mt to about 72 Mt CO₂e by 2010. For agriculture to achieve its share of the Canada’s Kyoto target (6% below 1990), emissions would have to decline to about 55 Mt CO₂e by 2010. The 10 Mt CO₂e BAU sink offset reduced emissions to about 62 Mt CO₂e, and reduces the gap to about 6.5 Mt CO₂e. If the sector could achieve the adoption rates modeled in the medium or high adoption scenarios, emissions could be reduced below 55 Mt CO₂e.

Under the rules negotiated for inclusion of sinks under Article 3 of the Kyoto Protocol, countries must report all sources and removal associated with afforestation, reforestation, and deforestation activities (Article 3.3). Countries can also elect to account for removals associated with cropland and grazing land management, revegetation, and forest management (Article 3.4) In the re-commitment period report due on January 1, 2007, countries must indicate what, if any, activities they will include under Article 3.4. It is likely that Canada will elect to account for GHG emissions and removals on cropland, grazing land and from forest management.

Modalities for accounting differ between Articles 3.3 and 3.4, and under Article 3.4, agriculture is accounting differently that forestry. Under Article 3.3, countries must account for all sources and removals associated with afforestation, reforestation and deforestation. However, because forests in northern countries in Canada are slow-growing, it takes many years for afforestration and reforestation to offset the loss of carbon resulting from deforestation. To balance the accounting, a provision was negotiated in the Protocol to allow for up to 9 Mt of sources from deforestation to be offset with C removals in the managed forest. Once the deforestation debit has been accounted for, additional sinks associated with the managed forest are capped, in Canada’s case at 12 Mt C per year. Forest sinks could therefore, total 21 Mt if the total deforestation debit was required.

There is no cap on agricultural sinks, which are accounting on a net-net basis as the net change in carbon stocks and emissions over the commitment period, less the net change in carbon stock and emissions in 1990 (times five since the commitment period is 5 years).

The domestic emission trading component applies to large industrial emitters, such as producers of oil and gas and thermal electricity, which will have emissions capped at about 94% of 1990 levels. The capping or emission permit allocation mechanism has not yet been finalized. Emitters in the capped sectors can purchase offsets domestically (agriculture and forest sinks) or internationally to help meet emission reduction targets.

All other sectors of the Canadian economy, including agriculture, are not capped and are included in the targeted measures component. A mix of policy options (e.g., incentives, disincentives) will be implemented to help those sectors reduce emissions. Agriculture and forestry will be able to sell above- BAU sinks credits into the covered sector.

International purchases will be used to close the "gap" if DET and targeted measures fall short of Canada’s emission reduction target by 2012.

In developing GHG mitigation options, stakeholders and researchers have identified practices that reduce emissions or enhance sinks in addition to other economic and environmental benefits. For example, in the agriculture sector, elimination of tillage summerfallow or adoption of reduced tillage systems occurred because of the economic and soil conservation benefits the practices offer, long before Canada committed to a GHG reduction target. The mitigation approach allows sectors to promote adoption of management practices for which the environmental and economic benefits are already known. Adaptation to climate change may not offer the same flexibility. In addition, the costs of adaptation are not known. It seems prudent at this time, therefore, to begin the mitigation process using management systems that offer multiple benefits.