Agriculture

Because agriculture is particularly weather-dependent, climate change is particularly important to those in this industry. Much of the Great Lakes Basin has a combined soil and climate regime that makes it a prime agricultural area, suitable for large-scale farming. The area has an average annual precipitation range between 24 and 42 inches, offers an average 145-day growing season, and has moderate levels of potential evapotranspiration (soil evaporation and plant transpiration) and solar radiation (sunlight). These conditions make this area suitable to produce 8 of the 10 top food crops in the world in large quantities as part of the 120 commodities grown or raised commercially in the region. Those commodities follow a north-south gradient with forests and cool-weather crops to the north and intensive row-crop monocultures (all one crop type e.g., corn) in the southern portions of this region.

There are at least five uncertainties related to climate change that could challenge agriculture in the Great Lakes region. They include: the level of regional change in temperature and precipitation including variability and extremes (e.g., late spring frosts, hail, storms, etc.); the magnitude of the carbon dioxide fertilization effect on crop yield; the ability of farmers to adapt to potentially new climate conditions (e.g., having water and/or irrigation facilities available); soil limitations that could prevent some crops from being able to take advantage of a warmer climate; and the state of the global market (e.g., commodity prices and access to global markets). However, the impact of each or all of these factors is difficult to predict because they are highly interconnected with other biological and socioeconomic (including government policies) factors.

Nevertheless, impacts on agriculture that could plausibly result from climate change are explored below. Social and economic impacts, closely related, are addressed together. Strategies that could help to avoid, or mitigate, these impacts conclude the discussion.

Projected changes in climate would have varying effects on this region's crops. Some of these changes could be beneficial in many situations to many crops. Generally, increased temperatures, a longer growing season, and increased levels of carbon dioxide contribute to increasing crop yield, especially if adequate water and plant nutrients are available. However, the effects of increased carbon dioxide concentrations on specific crops of the Great Lakes would differ and often depend on the accompanying temperature and precipitation changes. As well as often promoting growth, increased carbon dioxide levels allow some crops to use water more efficiently and have been shown to provide beans and cucumbers, for example, some protection from injury due to chilling temperatures. Certain weeds are also likely to benefit from higher levels of carbon dioxide, thus necessitating increased application of herbicides, which may lead to other environmental impacts.

While many crops are likely to benefit from warmer temperatures, longer growing seasons, and increases in atmospheric carbon dioxide (CO₂), an increase of several degrees actually could reduce photosynthesis (the process that plants use to absorb carbon dioxide from the atmosphere and convert it to sugars used for energy and growth) for crops growing near their optimum temperature. Such a response could result in shortening the growth period and reducing crop yield. The rate of plant development can also affect crop yield. Yields are reduced in grain-type plants when higher temperatures speed crops through their growth phases. In addition, brief high temperatures at critical stages in a plant's development can severely reduce the quality of some cool-season vegetables and fruit crops.

Because of the various factors that influence specific crop growth, investigator research results may differ on the projected overall impact of climate change on this region's crops. For instance, Andresen et al. (2000) found recently that for alfalfa (a forage crop), maize (a course grain), and soybeans (an oilseed) crop, yields in this region in the future may be substantially greater than yields of the 20^th century. These increases are likely due to varying combinations of CO₂ enrichment and the projected improvement in growing season weather (increases in temperature and precipitation), especially in northern sections of the region. This study suggests that the portion of the total water used by crops during the growing season will be more from precipitation than from the long-term soil moisture storage making moisture stress less likely than in the past. Their study also suggests a northward shift of some current crop production areas. EPA state-by-state projections suggest mixed results. For example, in Minnesota, corn yields could remain unchanged or could decrease by as much as 34 %, wheat yields could increase by 6 to 10 %, and soybean yields could be up by as much as 28 % or down by as much as 12 %.

Increased evaporation and reductions in soil moisture could worsen soil erosion and related sedimentation, exacerbating a problem challenging the agriculture industry in the US and the Great Lakes region. According to the USDA 1997 National Resources Inventory, more than 1 billion tons of soil erode annually, some of this from the nearly 30 million acres of cropland in the basin. This problem has seen improvement in many areas of this region since 1992. However, erosion could again increase if climate change brought increased winds as a result of more storms or an increase in heavy downpours.

Pollution, another environmental problem already challenging this region, could worsen with the effects of climate change. The agriculture industry is already contributing to pollution in the Great Lakes Basin through the use of pesticides, resulting in bio-accumulation of these substances in fish. Higher temperatures in the Great Lakes region are also likely to allow the survival of pests that normally do not withstand cold winters, resulting in additional threats to crops and livestock and the heightened need for pesticides. Applying these pesticides has the potential of creating additional environmental concerns.

Farm animals could be affected by changes in climate, although the ideal temperature for particular animals differs. Warmer winters could allow a longer stay outside for most farm animals, with less concern for low temperature impacts. Warmer summers, on the other hand, could impact dairy cattle for example. Dairy cattle perform best in cool climates (between 40_ and 75_ F) and are sensitive to heat stress. High relative humidity, which is often present in the Great Lakes area, exacerbates heat stress. With 80% relative humidity, heat stress for dairy cattle can occur at temperatures as low as 73_ F and become severe at 93_ F. Moreover, heat stress in dairy cattle can affect reproduction and milk production for as long as 180 days.

If favorable cool-climate conditions shift north into what are now natural ecosystems, as suggested by the Andresen et al. (2000) study results, environmental impacts could arise. If the conversion of forested land to agriculture occurs there could be an increased risk of ground and surface water pollution, an increased depletion of water resources, and loss of wildlife habitat. Such consequences could be offset or become a positive situation if existing farmlands revert to more natural states.

Agriculture ranks among the most important economic activities of the Great Lakes region. In the late 20^th century, agriculture accounted for more than $15 billion in annual cash receipts. The total area of cropland and pasture in the US portion of the Great Lakes Basin is about 28 million acres on nearly 600,000 farms. Livestock (half the total), dairy ($5 billion), and cash grain are the region's mainstays, but the area also supports a wealth of specialty crops (fruits, vegetables, and ornamentals). Farming also sustains a significant part of the social and economic fabric of life in the Great Lakes region, involving many of its residents and much of its land. In the 1980s, the fraction of the region's land area devoted to agricultural activities ranged from a low of 3% near Lake Superior to a high of 67% near Lake Erie, with the other 3 lakes ranging from 27 to 44 % of their basin land area devoted to agricultural use.

The agricultural importance of the Canadian portion of the region is even more critical to Canada than is the agricultural importance of this region to the United States. For example, although Ontario, Canada's only province located in the Great Lakes Basin, accounts for just 10% of Canada's farmland, it provides 25% of the total value of Canadian agricultural sales. About half of Canada's vegetables and much of its corn and soybean production also are based in the region. Grapes, tobacco, tree fruits, and nursery products also are grown in the region. Any negative economic impact from climate changes to agriculture in the Great Lakes region would thus be an additional stress on an important industry. Agriculture in the Great Lakes Basin accounts for 5.3 % of total agriculture employment for both United States and Canada.

In the past, much of the lost agricultural acreage in Michigan, Wisconsin, and Minnesota has been due to urban encroachment. According to EPA projections (1997), future climate changes in Minnesota would be likely to cause farmed acreage to decrease by 12 to 18 % and income to decrease by 10 to 25 %. The Michigan farmed acreage was projected to remain unchanged, but farm income was projected to decrease by 10 to 40 %. In Wisconsin, however, acreage and income were projected to be likely to remain largely unchanged, or income could increase substantially depending on the climate change impacts actually experienced. The Andresen et al., (2000) findings for significant increases in crop productivity and productive area (especially in the north of this region) would lead one to surmise an increase in economic benefit, however, that projection of increasing economic benefit has yet to be quantified.

Adjustments would be needed in farming methods to adapt to new climate conditions. Andresen et al, (2000) reports there is evidence that the agriculture industry in the Great Lakes region has the ability to at least partially adapt to a changing climate and that the costs of some adaptations could be small. For example, a switch to a longer season variety of crop, to earlier planting dates, or to double cropping (plant another crop after harvesting the first in the same season) would all be relatively straightforward and inexpensive. Their projections also suggest that in the future greater agronomic potential would exist for northern sections of the region than at present.

Greater frequency and severity of droughts and substantial reductions in summertime soil moisture are possible if variability in precipitation increases or if the increase in temperature increases evapotranspiration significantly. As a result, there is a potential for increased irrigation demand in certain localized areas. Specific portions of the region might need to invest in more water infrastructure to support increased agricultural needs for water. In Michigan, Minnesota, and Wisconsin, where the principal crops are varying combinations of corn, soybeans, silage, wheat, and hay, only 2 to 4 % of the farms are presently irrigated. Climate change would be likely to highlight the need to increase the number of acres that are irrigated, thus taxing water allocations and decreasing tributary flows into the Great Lakes system, causing a further drop in water levels, particularly in the summer. According to Andresen et al., (2000), creating incentives for farmers to utilize water more efficiently is one of the keys to the future viability of irrigated agriculture in regions that exhibit water scarcity. They also suggest that if farmers could decrease their water usage by even a small percentage, that reduction could diminish the possibilities for water conflicts and support the potential for economic growth in the region.

Other concerns include additional costs to farmers to take advantage of possible benefits from increased levels of carbon dioxide. These costs could include increased use of fertilizers, pesticides, herbicides, along with water for irrigation so that plant productivity could be sustained. Ultimately, the ability to adapt will depend on the nature of the climatic changes that actually occur in this region.

Strategies to mitigate or cope with climate stresses on agriculture in the Great Lakes region include the following options:

• Utilize more accurate regional climate projections and regionally relevant crop models to provide for improvements in forecasting and crop planning;
• Support agricultural research to develop alternative crop species and varieties;
• Develop markets for new crops adapted to climate changes;
• Renovate or construct controlled environment facilities for farm animals where they would be unaffected by severe weather events;
• Improve existing infrastructure to deal with a wider range or greater intensity of weather extremes (e.g., irrigation); and
• Develop policies to address potential climate-change impacts on agriculture, such as heightened flexibility in land use, farm loans, and government regulations and policies; alternative employment; and options to maintain community structure.