3B.3 Migration of agriculture to the Southeast as an adaptation to regional climate change

Monday, 18 July 2011: 4:00 PM
Swannanoa (Asheville Renaissance)
Richard T. McNider, Earth System Science Center, Huntsville, AL; and J. R. Christy

It is the purpose of this paper to discuss whether agricultural food, fiber and bio-fuel production can be sustained in the U.S. through a migration of production back to the Southeastern U.S. under an irrigation assisted rain-fed agricultural system. Migration of production back to the Southeast, if sustainable, would be an adaptation strategy to climate change and provide additional capacity for long-term food, fuel and fiber security. The assessment of this option requires the use of climate change projections, crop models and assessment of available water. In the 20th Century a massive migration of agriculture occurred in this country largely due to water and climate. Row crop agriculture in the Southeast underwent a significant decline in large part due to the inability of farmers to deal with drought compared to their competitors. In the early part of the 20th century Alabama, Georgia and Mississippi dominated in cotton production. Large amounts of corn were grown in almost every Southeast state for consumption by local livestock and poultry. Regional vegetable markets served the population. However, by 1980, Western irrigation and improvements in transportation had largely destroyed this distributed system of agriculture in the rural South. Irrigated cotton in Arizona, California and Texas replaced the cotton economy of the Deep South. Traditional vegetables were replaced by those grown in California. The SE was not alone in its decline in agriculture. Potatoes from Maine and Pennsylvania were supplanted after 1950 by potatoes from the irrigated Snake River Valley. In the last century the Nation's grain production became concentrated in the Midwest since deep water holding soils largely insulated farmers from drought losses and new locks and dams on the Mississippi and Tennessee rivers provided cheap water transportation to ship their more efficient product to the Southeast. The Southeast with relatively poor water holding soils and sporadic and highly variable growing season precipitation could not compete with competitors who did not incur significant drought losses. The result is that Alabama and Mississippi plant less than 10% of the corn they did in 1950 despite the fact they import huge amounts of corn in support of poultry and swine production. It is interesting that this loss of corn production was probably accelerated by short-term variability in climate in that the 1950's were the driest decade in many parts of the Southeast in the last 60 years. The remarkable U.S. agricultural production from irrigation in arid climates in the 20th century may contract substantially in the next century, and thus might affect US food security as a whole. Through irrigation, Western farmers were spared the droughts that had plagued Eastern farmers, but it is now recognized that the efficient Western system came with a price beyond what was paid in dollars. Water projects dried up the region's rivers. Salmon runs disappeared. Soils were poisoned from the salt in irrigated water that was left behind after evaporation. Water for irrigation in the West is now under stress due both to supply and demand . Tremendous urban population growth in the arid West has increased the demand for water. Supply is threatened on several fronts; ground water traditionally used for urban consumption is being depleted and cities are looking to supplies traditionally used for agriculture. Wringing the last drops of water in the West to sustain agriculture may be extraordinarily expensive, chaotic and in the end non-sustainable. The concentration of grain production in the Midwest leaves U.S. food and bio-fuel production vulnerable to long-term or severe mid-west regional drought. The Southeast may be in a unique position relative to climate change and population growth compared to other parts of the country and may most efficiently replace lost production in the West. While regional precipitation changes are uncertain, the IPCC concluded that dry areas are likely to become drier and wet areas wetter. It is also a hydrologic irony, that with the large water consuming natural vegetation in the SE, suburban and urban growth and land use change may actually reduce evapotranspiration so that population growth does not necessarily reduce water availability. Additionally, it is becoming recognized that substantial energy is being used to transport food and grains across the country from the West and Midwest. Returning agricultural production to the SE under irrigation might be efficient and environmentally sound. In the West, at least three to four feet of water per acre is needed every year to produce a good crop. In the East, only a few inches of irrigated water per acre are needed, because of the region's heavier rainfall. Even in a dry year for the SE, less than a foot of water per acre will suffice. Because of the huge size of the rivers in the East and the small amount of water required for Eastern irrigation, only a tiny fraction of the water in Eastern rivers would be needed for farming. Right now, the Tennessee River, with twice the natural flow of the Colorado River, has less than 1 percent of its water consumed for all uses, while the Colorado is just a memory when it reaches Mexico. There are concerns about expansion of agriculture in the SE under an irrigated scenario - will water resources be impacted, can water withdrawal in the winter be used for storage, will water quality suffer, it is economical to irrigate in the SE, what crops can be grown? This paper describes preliminary results of a major new NSF-USDA effort to address these concerns.
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