Sustainable cropping systems are those which provide the food and fibre needs of producers for both consumption and sale, while maintaining or improving soil, water and genetic resources for future generations. Greenhouse gas emissions from the livestock sector and energy consumption required for crop production, relative to energy content or output in commodities is drawing more international attention. Higher and more intensive production often requires more use of nitrogen fertilizer, the largest consumer of fossil fuel energy in agriculture and major source of greenhouse gases. However, conservation farming systems with diversified crop rotations have been shown to improve energy output per unit input ratios compared to conventional farming systems. More importantly, conservation tillage systems have been shown to improve soil and water conservation, increase water and nutrient use efficiency and increase soil organic matter (carbon) content. All of these benefits help minimize the production of greenhouse gases and enhance agricultural soils' capacity as a carbon sink. Unfortunately, agricultural soil sinks are not yet formally recognized internationally or included in the Kyoto Agreement as an important mitigation strategy against increased production of greenhouse gases.
In 1987, the Brundtland report "Our Common Future" brought world attention to problems such as global warming, ozone depletion, desertification, reduced biodiversity, increasing demands of a growing population, and the need for a global agenda for sustainable development. In 1990, the Intergovernmental Panel on Climate Change (IPCC) made up of several hundred scientists from 25 countries, concluded that emissions from human activities are increasing the concentration of greenhouse gases and that this could lead to a warming of the Earth's surface (and associated implications). In 1992, world nations met in Rio de Janeiro to sign the Climate Change Convention, an agreement to reduce greenhouse gas emissions. The IPCC released its second scientific assessment in 1995 stating the "the balance of evidence suggests a discernible human influence on global climate." A further international agreement, signed by 174 countries in Kyoto, Japan, in 1997, agreed to set specific targets for reducing greenhouse gas emissions. Most developed countries (including Canada) agreed (by 2008-2012) to reduce "human induced" greenhouse gas emissions by 6-7% below 1990 levels. For many of these countries, including Canada, this means reducing emissions by more than 20% from today's levels (since emissions have continued to increase over than last 10 years). However, the Kyoto treaty will come into effect, only when ratified by at least 55 countries representing 55% of total greenhouse gas emissions from developed countries.
There is still considerable scientific and political debate about the potential impact of increasing greenhouse gas concentrations and other factors affecting climate change. Needless to say, many people do not fully realize the implications of meeting their country's emission reduction targets. The energy and utility sectors will have to spend billions of dollars to reduce their emissions and/or retrofit to cleaner sources of energy. The purpose of this presentation is to discuss agriculture's challenges and opportunities in reducing greenhouse gases and getting agricultural soil sinks included in the Kyoto Protocol, not to debate the climate change issue or the rationale for our emission reduction targets.
The greenhouse effect is essential to the existence of life on this planet. The warming from the greenhouse effect is highly beneficial; without it, the average temperature on Earth would be about 33ºC colder, making life for humans, animals and plants quite difficult. The gases causing the apparent increased warming of the atmosphere are known as greenhouse gases. The most important greenhouse gases are water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs). There is little concern about water vapor but there is considerable evidence that the concentration of the other greenhouse gases -- CO2, CH4, N2O and CFCs - has been increasing steadily since the industrial revolution, almost certainly because of human activity. By 1992, CO2 had increased by 30%, CH4 by 145%, and N2O by 15%. Current rates of increase are 0.5% per year for CO2, 0.6-0.75% for CH4, and 0.3% for N2O. The global warming potential of these gases relative to that of CO2 for a 100-year time horizon is 21 for CH4 and 310 for N2O. If the current rates of increase continue, internationally respected scientists expect a significant impact on the earth's climate.
The IPCC predict that the doubling of the CO2 concentration, likely to happen within the next 50-60 years, would increase average global temperatures by 2º-4ºC, a rate of warming unprecedented in the last 10,000 years. In short, greenhouse gases can have a positive effect, as they warm the atmosphere and create favourable conditions for biological activity. But like many other things, too much of a good thing can lead to problems, and in this case, continued increase in these gases may lead to an "enhanced greenhouse effect" with uncertain, possibly disruptive and disastrous consequences. Despite the potential positive effects for Canadian agriculture, variability and risk will increase with climate change.
Agriculture occupies a large portion of global land area (about 35%) and more than any other human activity. Because of this scale and increasing intensity of agricultural activities to feed the growing world population, agriculture emits a lot of gases into the atmosphere. Globally, agriculture accounts for about 25% of the carbon dioxide (CO2), 50% of the methane (CH4), and 70% of the nitrous oxide (N2O) released via human activity. However, in Canada, primary agriculture only accounts for about 10 percent of Canada's total human induced greenhouse gas emissions. Furthermore, it is estimated that two-thirds of agriculture's emissions are from N2O and one-third from CH4, and a negligible quantity of CO2 emissions. Because of the recent increased adoption of conservation tillage, reduced summer fallow acreage, and use of more diversified cropping systems; the production sector of agriculture (particularly on the Prairies) is believed to be neutral or a net "sink" (based on model estimates in 2000) with respect to carbon dioxide (CO2) emissions. Saskatchewan, because of its leadership in adoption of direct seeding and conservation tillage, has been a net C sink in agriculture for several years. However, in the base year of 1990, carbon dioxide emissions from Canadian agriculture were believed to amount to about 7 Mt. While it is important to note that our CO2 emissions (from agriculture) have been declining it is also important that we acknowledge the increasing levels of methane and nitrous oxide emissions (primarily from of our growing livestock sector). However, this fact emphasizes the importance of complete and comprehensive accounting for greenhouse gases and if we are counting our sources then it seems fair and reasonable to include or account for practices that reduce greenhouse gases and enhance "sinks". This has been Canada's position in negotiations.
But what are sinks? Many people often confuse "sinks" with reservoirs or pools of carbon. A "sink" is essentially any process, activity or mechanism that removes a greenhouse gas from the atmosphere (eg. photosynthesis - growing trees or crops) or the opposite of a "source" which releases a greenhouse gas into the atmosphere (eg. combustion of fossil fuels or biomass). The ultimate objective of the international U.N. Climate Change Convention is to "achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic (human-induced) interference with the climate system." Furthermore, the Convention states that countries are to take measures to reduce emissions from sources and enhance removals by sinks. It states "Each Party (country) shall limit its anthropogenic emissions of greenhouse gases and protect and enhance its greenhouse gas sinks and reservoirs". Therefore, it is Canada's position, and that of several other countries that there should be no limit on relevant activities that can act as a sink and that their exclusion would contravene the objectives of the Climate Change Convention. Currently, only three specific sink activities are included in the Kyoto Protocol; namely, reforestation, afforestation and deforestation, all of which remain to be clearly defined. Human-induced land use and land use changes can directly alter the size and rate of natural exchanges of greenhouse gases among terrestrial ecosystems, the atmosphere and the ocean. Due to the dominating influence of natural forests and large areas of agriculture in Canada, the sinks issue and the inclusion of activities that enhance agricultural soils, sustainable land use and forestry interests are of utmost important to Canada. By 2008-2012, Canada must reduce its net emissions by 140 to 180 Mt (of CO2 equivalents) in order to meet its Kyoto emissions reduction target. The cost of meeting this ambitious emission reduction target through reducing emissions alone could have adverse effects on our economy and international competitiveness. Depending on the final rules for the treatment of biological sinks, options could be available at a much lower real cost to society that would not only help Canada and other countries meet their net emission reduction targets but also result in more sustainable land use practices globally.
Soils constitute a major portion of the carbon stored in terrestrial ecosystems and play an important role in the earth's carbon cycle. Estimates quoted by the Soil and Water Conservation Society (SWCS), range from 1500-2000 Bt (billion tonnes) for organic carbon and 800-1000 Bt as inorganic carbon. Cole et al. (1996) estimated that pre-cultivation stocks of C were 222 Bt on the present area of cultivated land and that present levels are about 168 Bt. Eswaran et al. (1993) estimated that the total mass of organic C stored in soil globally is 1576 Bt of which 32% is found in the tropics. It is estimated that the upper one metre of mineral contains more than twice the amount stored in terrestrial plant biomass and about double the atmospheric carbon pool (Post et al. 1982). Carbonate-C, which is present in large amounts in arid and semi-arid regions, also contributes to the total C content in soils. The IPCC (1995) have estimated that the historical carbon losses from agricultural soils have amounted to 55 Bt. The C stocks of cultivated soils in the U.S. are estimated to be 15.6 Bt and it is estimated that they have lost 5 Bt of C since cultivation began.
Most of Canada's land is forested with only about 5% suitable for farming or agricultural production. The Prairies, alone, account for about 80% of Canada's 68 M (million) hectares (ha) of farmland. Two-thirds of this farmland or about 45 M hectares is used for crops and improved pastures. The remaining one-third is largely "unimproved" pasture, native range, bush, sloughs or marshes. In 1996, about 6.3 M ha of the cropland was summerfallowed but the summerfallow area has continued to decline (from more than 10 M ha in 1980) until 1999. The pool of soil organic carbon in Canada's cropland is estimated to be about 6 Bt to a depth of 1 meter. Since cultivation of these croplands began, an estimated 1 Bt of soil organic carbon has been lost. Since most of the organic carbon is near the soil surface (0-15 cm), it is most vulnerable to potential loss due to erosion and mineralization. Most of the soil C losses occurred in the first 25-30 years of cultivation, after which the rate of loss slowed when the readily decomposable soil organic carbon was depleted, and as farmers gradually adopted improved soil management techniques. Much of Canada's 20 M ha of grassland is extensively managed with seasonal grazing. If overgrazed, the pasture grasses will have their ability to sequester carbon significantly reduced. Under grazing also reduces the ability of grasses to maximize carbon sequestration, as the length of vegetative growth during the growing season is shortened.
Soil scientists agree that it is possible to restore soil organic carbon levels to near their pre-cultivation levels with significant nutrient inputs and adoption of the best land management practices. However, realistically it may be difficult and require several decades to sequester sufficient carbon to fully restore degraded agricultural soils to their pre-cultivation levels of carbon. Research has shown that it is possible to sequester from 0.1 to 0.3 t C/ha/yr for several years with the adoption of intensive no-till cropping systems but the total C gains will be dependent on soil type, crop rotation and weather conditions. It may be possible to sequester 1-3 tonnes of C/ha on most prairie soils with the adoption of the best management practices over a 10-15 year period. But obviously the quantity of C sequestered will be dependent on the rate of adoption of conservation tillage practices, commodity prices and cropping systems that are economically attractive in the future.
A variety of agricultural land management practices have been identified that can increase soil C content and improve the sustainability of the farming operation, including:
Although soil C can be increased with the adoption of these management practices, their adoption may also result in increased emissions of nitrous oxides or methane. Therefore, the benefits of additional C sequestration may be more than offset by the emissions of other greenhouse gases. So it is important to be aware of the potential risks and trade-offs. Unfortunately there are still great uncertainties about the associated CH4 and N2O emissions associated with many of the best C sequestration practices.
As discussed earlier, good land management practices can result in higher levels of soil organic carbon. But many decades of research on soil organic matter have also demonstrated that C stock changes occur relatively slowly and there is considerable landscape variability of soil C content. Typically it requires 5 years or more to measure statistically significant C stock changes as a consequence of land management change. Developing measurement and verification techniques to determine C stock changes is one of the greatest concerns of the international community in the context of the Kyoto agreement and inclusion of soil sinks. It is difficult enough in measuring C changes on relatively uniform research plots but detection of C stock changes on landscape or regional scales will offer even greater challenges. Some of the best management practices can sequester 0.2 t/ha/yr, but since we are attempting to measure this small change against a background level of at least 50-60 t/ha with considerable variability it should be apparent how critical it is to establish representative benchmark sites with uniform sampling protocols and the same subsequent measurement and monitoring protocols with GIS/GPS technology where possible. The GEMCo/TransAlta/SSCA/MII sponsored Prairie Soil Carbon Balance project was established in Saskatchewan to develop an appropriate measurement or model protocol to determine C stock changes on a large prairie landscape basis. This innovative project involving more than 25 scientists and 150 producers has shown that we are able to develop appropriate monitoring protocols with associated models that can effectively measure and verify C stock changes on a landscape basis at a reasonable cost.
Greater soil carbon changes (0.3-0.4 t/ha/y) can occur when moving from a less intensive (summer fallow) conventional tillage system to a more intensive (continuous cropping) direct seeding system; however greater inputs and some additional risk is also required. Even greater C stock increases (0.5-0.8 t/ha/y) can be observed when taking marginal cultivated land out of crop production and establishing grasses or legume forages. Agro-forestry offers good opportunities in the longer term for significant C sequestration as well. Needless to say economic considerations will be the most important driver in the short term since it is unlikely that the market value of C alone will justify major land use changes that sequester additional C compared to traditional or existing land use practices. The total C sequestered on a regional or national basis will depend on degree of adoption, benefits from practices and other financial or social incentives. Some of the future research and development needs associated with the measurement and verification of soil carbon stock changes on a regional or national scale include determining the potential application of new developments in remote sensing, selection of appropriate benchmark sites on representative landscapes of both cultivated and pasture lands, process studies to better understand nutrient cycles associated with alternative crops, potential benefits of precision farming and development of simpler and more appropriate models that can characterize the landscape practices on prairie ecosystems.
One might assume that it should be relatively easy to gain national and international support for agricultural soil sinks and land management practices that enhance C-sequestration when one considers the number of secondary benefits of improving C-sequestration in agricultural soils. The principles of soil and water conservation are universal and practices that add organic matter to the soil generally improve soil and water conservation with the associate benefits on the environment. Less wind and water erosion means less contamination of surface and groundwater with sediment and pesticides. It is also well documented that there is a strong correlation between soil organic matter content and productivity. Soil carbon content is still the most important indicator of soil quality. Soils with optimum levels of organic matter will not only support higher levels of productivity under adverse environmental conditions but these soils will help buffer and filter the adverse effects of pesticides and nutrients. Biological activity and biodiversity are much greater in good quality soils than in soils with little or no organic matter. In the international context we can identify several countries that have severe soil degradation problems and describe the potential benefits of more sustainable land use practices and C sequestration opportunities. There is growing evidence that conservation tillage systems have a positive impact on wildlife habitat. We also emphasize the relevance of C sequestration to other international U.N. Conventions, specifically the Desertification, Biodiversity and Wetlands Conventions. Despite these many important and fundamental secondary benefits of C sequestration, many countries still have major concerns about including agricultural soils as potential C sinks in the Kyoto agreement. The primary concern seems to be the potential size of the sink and offset that could be used or abused by Canada and the U.S. to reduce their commitment to reduce emissions of greenhouse gases. However, there are other concerns that will be discussed in the next section.
In addition to the primary concern about the potential size of the C-sink in North America the EU and other countries have expressed their reservations about including C-sinks in the Kyoto agreement for a number of other reasons. Some of the technical reasons for not including sinks include: difficulty and cost of measurement and verification of C stock changes, how to separate natural C change from man-made C change, universality and costs of reporting for many countries; vulnerability of losing stored C, greater emphasis on intensification and higher herbicide inputs, uncertainty about associated effects on other greenhouse gases. Many of these concerns are legitimate and warrant further discussion on how we can minimize these concerns and reduce the uncertainties but in our view, the collective concerns and uncertainties are not substantive and when weighed against the potential benefits of enhancing agricultural soil sinks it seems illogical, counter productive and potentially a perverse incentive not to include agricultural soil sinks in the Kyoto Agreement. Again, it is the potential size of the forest sinks in the U.S. and Canada that seems to be the primary concern of the EU countries.
The primary purpose of the Sixth Conference of the Parties (COP6) at the Hague was to clarify the rules for implementing the Kyoto Agreement and resolve the outstanding concerns associated with emissions trading, compliance, technology transfer, the clean development mechanism and sinks. We were optimistic that there would be agreement on including additional sink activities (like cropland management, grazing land and shelterbelts). Canada's objectives have always been clear. We want to maximize are ability to meet our greenhouse gas reduction commitments at the lowest possible cost through aggressive pursuit of Kyoto mechanisms, including sinks. To contribute to global climate change objectives and maintain a level playing field with Canada's trade competitors and encourage maximum participation of both developed and developing countries. Canada has always wanted to maximize the opportunities for Canadian businesses and industries to participate in international climate change projects. Canada has estimated that our forest and agriculture sinks during the first commitment period (2008-12) will be 35 Mt/y and 15 Mt/y, respectively, of CO2 equivalents. Combined, these potential sinks for forestry and agriculture only represent about 15% of our country's emission reduction targets. Therefore is should be clear that we are not attempting to avoid our commitment to reduce greenhouse gas emissions. We still must make substantial reductions in our consumption of fossil fuels and reduce greenhouse gas emissions to meet out targets by 2010.
Although considerable progress was made on technical issues and apparent agreement on limited or qualified inclusion of sinks, negotiations failed at the eleventh hour because a few EU countries continue to object to the inclusion of sinks in the Kyoto agreement. The U.S., Canada and Japan and other umbrella group (UG) countries were willing to accept significant discounts on their forestry sinks and a small discount on agricultural sinks; but some EU countries wanted caps on the sinks and this would discourage incentives to increase or enhance sinks which is one of the important objectives of the Climate Change Convention.
There was little or no consensus among the EU countries and they did not seem prepared to negotiate or move from their longstanding position on sinks. They appeared to be supportive of the UG proposal (to phase-in sinks) until the media learned of this support and then the EU position changed and they were unwilling to consider our proposal or to offer any counter proposals. An additional problem at COP6 was the demand by most developing countries (China and the G77) for several billion dollars for technology transfer even though they are not required to reduce their growing greenhouse gas emissions. There is also a major split among the G77 block in their position on sinks, partly driven by the lack of a clear understanding of sinks among many of the African countries. The compromise paper proposed by the Dutch President of COP6 was unbalanced (in favor of the EU position) and there was insufficient time to resolve the more contentious issues. However, the lead negotiator for the EU (from France) agreed to a counter proposal from the UG countries on the final day and we thought we had a deal. Unfortunately a few EU countries would not accept the deal. Negotiations were suspended and COP6 was scheduled to resume in Germany in late May of 2001. However, there was an effort by the EU and UG countries to attempt to resolve some key differences at an Ottawa summit meeting in late November (before Clinton left office). This meeting helped clarify views and move the process forward but there was still no commitment (by the EU) to agree to include sinks. The EU acknowledged that it was also important for them to reach a consensus on their positions (or degree of flexibility) prior to the next formal round of negotiations in May.
In view of the many benefits of soil sinks and the IPCC Special Report (on the science of sinks), many countries acknowledge the potential impact of sinks but are reluctant to support their unqualified inclusion in the Kyoto Agreement. There is considerable concern that some countries will use sinks to avoid their emission reduction commitments. The inclusion of sinks will depend on getting support from the EU and the other Parties. If they are included there will likely be discounts or caps on the size of the C sink offsets (particularly for forestry sinks). They (sinks) will also have to be measured and verified using universally accepted and technically sound protocols. Canada and other UG countries firmly believe that soil sinks should be included in the Kyoto Agreement, not only to help offset the growing emissions from the agriculture sector (which will be costly and difficult to reduce), but because of the many universal secondary benefits. Canada has stated the inclusion of sinks is a condition of ratification. With or without a Kyoto Agreement Canada is committed to reducing greenhouse gases and enhancing soil and forestry sinks. We will continue to provide technical arguments and good science in our negotiations with the international community. There is need for further discussion with stakeholders on potential credit for early action to ensure we maintain the progress being made with the adoption of more sustainable land use practices. We have identified some important research and development needs to help strengthen our science both nationally and internationally. We will continue working with stakeholders to develop appropriate action plans and policies that will help us meet our international commitments in reducing greenhouse gases. We continue to require industry support and ongoing discussions and cooperation with all of the important producer groups. Needless to say without the support and cooperation of farmers and their continued adoption the best management practices the likelihood of sequestering significant quantities of carbon is limited. Agriculture may only be 10 percent of the greenhouse gas problem for Canada but potentially it can be a much greater proportion and cost-effective part of the solution if we continue to adopt more sustainable land use practices. There is obviously a greater incentive for adoption if farmers and countries get credit or recognition for the CO2 sequestered as soil C. Many prairie farmers have been sequestering soil C for several years and helping mitigate against global warming. With the appropriate incentives and international recognition it is likely many more producers will become engaged in Canada's commitment to protect the environment and reduce greenhouse gas emissions.
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