It is expected that an initial increase in CO2 will actually behave like a fertilizer and enhance the growth of crops such as rice, wheat, and soybeans. The IPCC cautions, however, that even though it may initially increase production, there will be a slowing that occurs as temperature and precipitation changes may counteract the "beneficial CO2" effects.
When looking strictly at North America, research by the IPCC in their 2007 report concluded: "Moderate climate change will probably increase the production of 'rain fed' agriculture." Estimates of the increases, however, have been lowered from what they once were. Over the next few decades, agricultural yields are expected to increase by 5 to 20 percent. Food production is expected to benefit some areas of the continent but decrease in others. The U.S. Great Plains/Canadian prairies regions are expected to be some of the most vulnerable to climate change. They have also determined that the crops grown closest to climate thresholds (regions of abrupt change) such as California's wine grapes will suffer the most serious decreases in yields and quality. Crop production in the Southern Plains, Appalachia, the Corn Belt, and in the Delta States are expected to have a decrease in productivity of 16 to 21 percent. On the other hand, fruit crops in northern regions such as the Great Lakes and eastern Canada are expected to increase because the length of the growing season and temperatures will increase. Northern Europe is expected to produce an increase in cereal crops. The low-latitude (tropical) countries are expected to have a decrease in grain production.
Overall, vulnerability is also economic in nature. The agriculture in developed countries—such as the United States, western European countries, Canada, and other industrialized countries—is expected to be less vulnerable than the agriculture of developing nations, such as countries in the Tropics. In the poorer nations, problems arise because farmers have limited opportunities to adapt because they lack the land, equipment, capital, and technology.
Land management practices are a critical issue when farmers are faced with global warming. By varying which crops are grown from season to season and using new technology, farmers can better adjust appropriately to climate change. As food becomes scarcer and demands are put on the land, different areas of the world will experience different degrees of hunger. Those that will be affected the most are in the developing countries of Africa, Asia, and South America.
The IPCC has also warned that impacts to agriculture will become more severe as climate change continues. If CO2 concentrations rise beyond double what they are today, then damages may become a significant loss to the U.S. agricultural economy. In other words, as CO2 levels continue to rise, even areas that experienced a temporary increase in yield will suddenly face a decrease in yield. In addition, there will also be a northern shift in invasive weeds.
Disease pressures on crops and domestic animals are also expected to increase with earlier springs and warmer winters, which will allow rapid reproduction and higher survival rates of pathogens and parasites. The regional distribution of warming and changes in rainfall will also affect the spatial and temporal distribution of disease. According to the U.S. Climate Change Science Program, the following list defines their findings related to rangelands and pasturelands:
• Projected increases in temperature and a lengthening of the growing season will likely extend forage production into late fall and early spring, thereby decreasing the need for winter-season forage reserves.
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Future Food Production
Regional Change in Cereal Production by 2050-80s
Decrease (-8 to -9%)
Small increase (2 to 4%)
Small decrease (1 to -10%)
Increase (1 to 20%)
Small change (-4 to 8%)
• In both pasture and rangelands, shifts in optimal temperatures for photosynthesis might be expected under elevated CO2.
• Climate change-induced shifts in plant species are already under way in rangelands. Establishment of perennial herbaceous species is reducing soil water availability early in the growing season.
• Increasing CO2 will alter forage quality; in nitrogen-limited native rangeland systems, CO2-induced reduction in nitrogen and increase in fibrous plants (woody shrubs, trees) may lower quality.
The following list pertains to their findings relating to animal management:
• Higher temperatures will very likely reduce livestock production during the summer season.
• For ruminants (cattle), current management systems generally do not provide shelter to buffer the adverse effects of changing climate; such protection is more frequently available for nonru-minants such as swine or poultry.
• Benefits from extended forage season production and reduced need for winter-season forage reserves will very likely have significant impact on livestock operations.
• Shifts in rangeland and pastureland plant productivity and type will likely have a significant impact on livestock operations.
According to the Pew Center on Global Climate Change, the added stress of global warming could add enough stress to threaten local or regional food supplies. In addition, population growth, economic hardship, poor land management practices, and political instability can impair a nation's ability to feed its population and cope with global warming. The IPCC estimates that even without climate change, the number of
(opposite page) Climate change will threaten food security worldwide with the largest impact to developing countries.
people at risk of hunger and malnourishment will increase from 500 million currently to more than 640 million by 2060. Global warming will increase those numbers. In terms of food security, sub-Saharan Africa is at most risk for food scarcity. Lacking rainfall and having a high level of evapotranspiration, more than half of its land is irrigated. It is also very low in organic matter, making it highly nonfertile.
According to a report in Discovery News, farmers hoping to use desalinated water as a resource in water-scarce areas to irrigate crops have had to overcome a hurdle. At a desalination plant currently operated in Israel, it was determined that the converted water was lacking in calcium and magnesium, but was overloaded with boron. While not a problem for drinking water, it was for the production of crops—but with the addition of fertilizer and some other adjustments, the water could be treated so that it could be safely used for irrigation.
Farmers also discovered that using desalinated water also helps reduce the existing salt content in soils—particularly those soils found in the arid and semi-arid regions of the world. While desalinated water was not originally intended to be used as irrigation water, the concept is slowly gaining ground, currently being used by Australia, Israel, and Spain. Currently, 69 percent of the global water supply is used for irrigation.
According to Andrew Chang, director of the Center for Water Resources at the University of California, "Desalinated water hasn't yet made it into agricultural use in the United States, but that's not to say it won't someday."
Currently, a municipal desalination plant in Santa Barbara, California, is functioning as a reserve against drought. As global warming intensifies, desalination may become a key factor in providing a critical resource for both drinking and agricultural water. As technology becomes more sophisticated, scientists will continue to work on better ways to manage global warming issues.
Because the agricultural sector is critical to everyone on Earth, it is especially important to understand the cause-and-effect relationship between it, greenhouse gases, and global warming. Public education is especially important in order to be assured of maintaining an adequate global food supply.
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