Adaptation Strategies

Agriculture in the United States and Canada has many strong points in its favor to permit successful adaptation to climate variability and climate change. The overall production system is technically advanced and can adopt new technology rather quickly. It is regionally diverse, making adaptation to a wide range of conditions quite feasible (IPCC, 2001). The agricultural sector is highly productive, intensively managed, and market based. Further, agriculture accounts for less than 5% of the national gross national product (GNP), allowing considerable flexibility to adapt to changes required in the production system. At the same time, it would be prudent for agriculture to take advantage of any positive opportunities offered by climate change in order to maximize production efficiency and remain competitive in the international marketplace.

U.S. agriculture is vulnerable to rapidly changing climate conditions. The range over which major crops are planted could eventually shift hundreds of kilometers to the north. The availability of fresh water and the distribution of pests and diseases may have significant impacts on production potential. The goals of adaptation strategies are to improve the knowledge and skills of farmers, to encourage adoption of new technologies, and to expand the array of options available to farmers.

One option of the research community is to continue to develop new ways for certain crops to adapt to climatic constraints, such as warmer or colder temperatures, and drier conditions. More recent innovations in biotechnology offer promising new techniques. Newtissue-culturing and genetic-engineering tools, combined with traditional agricultural breeding methods, alter plants to incorporate greater disease, insect, and weed resistance, and to better withstand environmental stresses such as drought, heat, and frost. Efficient water resource planning is also an essential aspect of adaptation strategies for agriculture.

Erosion in the Great Plains was reduced after devastating losses of valuable topsoil during the dust bowl years of the 1930s by planting shelterbelts of trees to reduce wind erosion. Reduction of summer fallow practice and move to minimum or zero tillage are management practices which have reduced erosion and promoted higher soil organic matter (McRay et al., 2000, Chapter 7). Other means of alternative agriculture included systematically incorporating natural processes, such as nutrient cycles, nitrogen fixation, and pest-predator relationships into the agricultural production process; reducing the use of chemicals and fertilizers; making greater use of the biological and genetic potential of plant and animal species; improving the match between cropping patterns and the productive potential and physical limitations of agricultural lands in order to ensure the long-term sustain-ability of the land; and, emphasizing improved farm management and conservation of the soil, water, and biological resources (World Resources, 1992).

U.S. agriculture is vulnerable to rapidly changing climate conditions. The range over which major crops are planted could eventually shift hundreds of kilometers to the north. The availability of fresh water and the distribution of pests and diseases may have significant impacts on production potential. The goals of adaptation strategies are to improve the knowledge and skills of farmers, to encourage adoption of new technologies, and to expand the array of options available to farmers.

Having noted this, however, it must also be said that given the uncertainties and serious consequences of potentially inaccurate assessments, a prudent course of action is to aggressively study and research how best to limit and mitigate the impacts of climate change or agriculture. Complacency poses great risk. A vigorous effort is needed to understand and prepare for potentially serious impacts on agriculture by developing strategic adaptation strategies.

Crop yields and variability under climate change (historic baseline and 2 x CO2 scenario) and adaptive crop management scenarios (planting dates; harvest dates; fertilizer applications; tillage practices) were assessed for the major agricultural regions across Canada, using the EPIC simulation model (De Jong et al., 2001). EPIC (version 5300) integrates the major processes that occur in the soil-crop-atmosphere management system, including hydrology, weather, wind and water erosion, nutrient cycling, plant growth, soil temperature, tillage, plant environmental control

TABLE II

Summary of crop yields and standard deviations as simulated by EPIC for baseline (1966-1995 period) and a future climate scenario (2041-2060 period) for selected locations in Canada

Yields (Mg/ha)

Average Std. Dev.

Yields (Mg/ha)

Average Std. Dev.

Crop

# sites

Baseline

2 x CO2

Baseline

2 x CO2

Barley

29

3.5

3.5

0.77

0.94

Spring wheat

25

2.8

2.7

0.85

0.91

Canola

12

2.5

2.6

0.89

1.03

Corn

6

5.7

5.0

1.73

1.99

Soyabeans

6

2.0

2.2

0.56

0.83

Potatoes

5

6.7

7.9

0.81

1.01

Winter wheat

3

3.5

4.2

0.67

0.77

Source: Results were taken by A. Bootsma from: De Jong, R., Li, K. Y., Bootsma, A., Huffman, T., Roloff, G., and Gameda, S. 2001. Crop yield and variability under climate change and adaptive crop management scenarios. Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Ottawa, Ontario, Climate Change Action Fund Project A080, Final Report. 49 pp.

Source: Results were taken by A. Bootsma from: De Jong, R., Li, K. Y., Bootsma, A., Huffman, T., Roloff, G., and Gameda, S. 2001. Crop yield and variability under climate change and adaptive crop management scenarios. Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Ottawa, Ontario, Climate Change Action Fund Project A080, Final Report. 49 pp.

and economics. Under a warmer and slightly wetter 2 x CO2 climate scenario, the planting dates advanced 1 to 2 weeks in eastern and central Canada and by approximately 3 weeks in western Canada. Yields of spring planted barley, wheat and canola (prairie region only) did not change significantly (Table II). Corn yields in central Canada decreased significantly by 11%, although with increased nitrogen fertility the yield decrease was reduced to less than 5%. With the projected longer growing season, higher yielding corn hybrids with higher heat unit regimes may also negate the projected yield declines. Soybean, potato and winter wheat yields increased by approximately 12%, 16% and 18% respectively. The temporal yield variability of all crops increased under the 2CO2 scenario from 6% for spring wheat to 50% for soybeans. The reduction in corn yields predicted by the EPIC model is probably the result of water stress, as other studies have suggested that even many areas in central Canada (Ontario/Quebec) may, like soybeans, have increased corn yields as a result of being able to grow longer season, higher yielding hybrids with the higher heat units regimes.

Based on the assumption that at least 2400-2500 crop heat units must be available for the crop to mature, corn and soybeans could be grown under the 2 x CO2 climate scenario at all locations (29 climate stations in 17 ecoregions selected across Canada) - except some of the most northern ones. When water stress was not a limiting factor, corn and soybean yields were comparable to those simulated in central Canada where these crops are currently grown.

McGinn et al. (2001) generated regional climate change scenarios for the Canadian Prairies using historic weather data and daily data from two Canadian Climate Centre Global Circulation Models. The climate change scenario data included daily maximum and minimum air temperature and precipitation data generated using the Canadian Centre for Climate Modelling and Analysis second generation Global Circulation Model (GCMII) and their newer coupled (linking ocean and atmospheric processes) GCM with atmospheric aerosols (CGCMI-A). In addition, a combination of each GCM temperature and the historic precipitation (HP) amount and frequency were used to generate a third (GCMII HP) and fourth (CGCMI-A HP) climate change scenario.

All scenarios were used to drive the modified Versatile Soil Moisture Budget model that assesses soil moisture, aridity and other agroclimatic indices. The results from the four climate change scenarios were compared to those using the historic climate data. With spring warming occurring earlier the provin-cially averaged advancement of seeding dates varied between 16 and 29 days depending on the chosen scenario - in more southern regions an additional 23 days compared to the provincial averages. All four climate change scenarios predicted increases in the number of degree-days between 3% and 22% (provincial averages). Greatest warming during the growing season was anticipated in Alberta. Soil moisture was predicted to increase between 22% and 34% using GCMII scenario, coinciding with the large predicted increase in precipitation. However, little change in soil moisture was predicted under a CGCM1-A scenario.

Climate change with warming but no change in precipitation (GCMII HP and CGCM1-A HP) resulted in a 10% decrease in soil moisture in Alberta and no change in Saskatchewan and Manitoba. Aridity during the growing season was predicted to decrease dramatically under a GCMII scenario (wetter conditions) to only slight changes with the remaining scenarios. Both GCM output data resulted in a shift to earlier seeding dates and an improvement in soil moisture status on the Canadian Prairies. Even under the worst-case scenario (no change in annual precipitation amount or pattern), the shift in seeding dates compensated for increased evaporation during the summer - only. Alberta was predicted to experience a decrease in soil moisture. It should be noted that these projected changes in soil moisture are based on the advancement in the growing season dates and decreased maturity period. The adoption of earlier seeding dates with conventional short-season crops was an adaptive strategy that resulted in water savings.

Without this adaptive strategy, production of cereal crops in the Prairies is expected to drop by up to a third in western areas and increase by up to two-thirds in eastern areas due to changes in available soil moisture. Ontario and Quebec will experience similarly variable results. In both the Atlantic Region and British Columbia increased grain yield potential is foreseen but realization of this potential is likely dependent on the amount of water available for irrigation (Environment Canada, 1997b).

Agroclimatic indices (heat units and water deficits) were determined for the Atlantic region of Canada for the present day climate (1961-1990) and for two future periods (2010-2039 and 2040-2069) using the output from the Canadian GCM (Bootsma et al., 2001). The climatic changes expected to occur within the next 50 years, based on the Canadian GCMI model and a "business as usual" scenario for Green House Gases emissions, are likely to have significant impacts on crop production. Crop (Corn) Heat Units (CHU) would increase by 300-500 CHU for 2010-2039 and between 500-700 CHU for 2040-2069 in the main agricultural areas of the Atlantic region. Anticipated changes in water deficits, defined as the amount by which evapotranspiration exceeded precipitation over the growing season, were generally less than 50 mm for both periods, increasing in some areas and decreasing in others. Statistical comparisons of crop yields with climate indices suggest that yields of grain corn and soybeans could increase as much as 3.8 and 1.0 tonnes per hectare, respectively, by the year 2055, mostly as a result of increased availability of heat units. Changes in water deficit are not expected to have a significant impact on crop yields. Yields of barley are likely to change only slightly but the competitive advantage in relation to corn and soybeans will be significantly reduced and likely lead to major shifts in areas seeded to these crops.

Grasslands are an important carbon and methane sink. Mitigation strategies for grasslands focus on small to moderate improvements in soil carbon levels, primarily through the prevention of overgrazing which leads to dramatic changes in plant species, decreased plant growth, and potential desertification. Improved management of grasslands can result in small increases of carbon sequestration per unit of land. In contrast, the biological process of denitrification releases nitrous oxide and enteric fermentation by cattle grazing the forage on grassland releasing methane. The complexity of issues involved can be illustrated by the following interaction. Some of the mitigation strategies that have the potential to increase soil carbon sequestration could result in increased nitrous oxide and methane emissions due to improved soil fertility and increased cattle numbers on the land. For cultivated land, soil carbon sequestration is dependent upon three key factors: land tillage practices, plant species selected, and soil nutrient and water inputs. Minimum or zero tillage initially was recognized as an important tool for reducing soil erosion and improving water conservation. However, low-tillage soil management has also been recognized as an effective means of soil carbon sequestration. There is increasing consensus that summer fallow acreage will also reduce N2O emissions.

As noted earlier, nitrous oxide occurs as a result of the denitrification processes in the soil. Soil carbon and nitrogen cycles are linked. Therefore, land management strategies directed toward the incorporation of atmospheric CO2 into soil organic matter must be evaluated relative to the impacts on N2O emissions. For example, the portion of N2O that is produced near the soil surface or that is not able to be absorbed at deeper levels through downward diffusion due to an inhibiting layer will result as N2O flux into the atmosphere. An inhibiting layer is, for example, a frozen ground layer in the spring. Thus, a greenhouse gas mitigation strategy relative to soil nutrient management is to reduce this soil N2O flux into the atmosphere.

A major complication to an effective strategy is the complex and rather poorly understood mechanisms that govern conditions for N2O production and emission from agricultural soils. Seasonal distribution of N2O emissions have been well characterized; however, the ability to quantify these emissions has been difficult. A number of factors influence nitrification and denitrification processes, the time lag between production and emission of soil N2O, and the relationship between production and emission rates of N2O. These include rainfall, snowmelt, temperature, freezing and thawing, fertilizer and manure applications, and tillage.

Although agriculture is a net emitter of green house gases, farmers can adopt several measures to reduce emissions (Desjardins et al., 2001). Some of these are expensive, but some can be used with little cost or even at higher profit. Widespread use of such practices could reduce emissions of all three green house gases, and for CO2, even make farms net absorbers (Janzen et al., 1998). Practices that are relevant to GHG emission reduction and sustainable development include: reduced tillage intensity; reduced summer fallow area; improved manure management; improved feeding rations; improved drainage/irrigation. Other considerations that come into play include their practical feasibility, economic cost, effect on soil quality, and influence on the whole environment. The projected effects of the above selected practices on GHG emissions and on other considerations are illustrated in Table 16 of The Health of Our Air (Janzen et al., 1998).

Water management practices and trends have a direct impact on greenhouse gases. Soil water content influences the timing, nature, and magnitude of soil mi-crobial processes which are responsible for the production and consumption of CO2, CH4, and N2O. Further, wetlands and bogs represent areas of significant carbon accumulation due to high plant productivity, coupled with the inhibition of organic matter oxidation.

Wetlands currently cover 14% of Canada's land mass ands are a critical resource providing habitat for species (including some of Canada's rare, threatened, or endangered ones), storage for atmospheric carbon, nutrient and mineral cycling, water purification, and natural flood control. Climate change could result in the conversion of semi-permanent wetlands from open-water dominated basins to vegetated areas (Environment Canada, 1999). Wetlands in Canada's agricultural zones are considered to be product ecosystems and are a net sink for greenhouse gases. In some areas, a promising mitigation strategy would be to return those lands that are marginally producing or that are increasingly subject to salinization to either permanent grass cover or to wetlands.

Opportunities for reducing emissions through increasing C sequestration exist by using improved farming practices and thereby modifying the soil climate and other physical soil properties, but the net effect is complicated. For example, the increase in soil moisture associated with no-till or reduced tillage leads to more soil decomposition, whereas the cooler temperatures and less soil aeration lead to less soil composition. But no-till has also other benefits such as minimizing C loss associated with soil erosion and savings in fossil fuel emissions because of reduced machinery use. In fact, no-till is the most efficient management practice for sequestering C in cropland, when compared to cover crops, crop rotation, fertilizer strategies and manure applications (Desjardins et al., 2001).

Large expanses of Canada's land base is forested land. It has already been noted that trees have the potential to trap atmospheric CO2 and sequester carbon. Planting shelterbelts have traditionally been an effective means of protecting agricultural or grazing land from strong winds. Plants and livestock can be subjected to severe stresses associated with excessive chilling, high temperatures, dessication, or direct wind injury. Windbreaks can, by reducing these stresses, be profoundly beneficial to the growth of plants and health of livestock. Thus, an effective mitigation strategy is the planting of trees on the landscape that is normally devoted exclusively to agricultural production. In addition to sequestering carbon, shelterbelts have the potential to reduce N2O emissions. There would be less fertilizer nitrogen applied to the land. More trees would mean less nitrogen moving out from the root zone to surface or groundwater resources (i.e., less denitrification). Finally, nitrogen would be recycled from the tree leaves that fall to the ground, reducing the need for nitrogen application to the soil.

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