There was never any 'empty' prime farmland on which to produce the increasingly large crop of Federally subsidized ethanol-corn (see Figure 1). Over the last decade, agricultural land use was swapped to get the job done. Whether a coincidence or not, a steep uptick in ethanol production kicked in as "W" took office and, according to USDA data, "the simultaneous net expansion of corn and soybean acreage resulted from a reduction in cotton acreage, a shift from uncultivated hay to cropland, and the expansion of double cropping (consecutively producing two crops of either like or unlike commodities on the same land within the same year)."Several important insights follow from the USDA land use acreage swap information. Mostly negative on the environmental side. This is strong evidence that House Republicans were right to push for eliminating Federal corn-ethanol subsidies: we were headed rapidly to a point where more corn would be used to feed cars and trucks than livestock!
Accidental Environmentalists: Republicans were right to argue for removing ethanol subsidies, but wrong to cut conservation reserve budgets.
Grass or "hay" lands typically erode very little - soil loss even on relatively steep hay fields will be in the 1 to 4 tons-per-acre-per-year range (generally regarded as sustainable). The same land, converted to corn, however, may result in an order of magnitude more soil loss, especially if "double-cropping" takes place.
The resultant increase in soil loss under corn is doubly unfortunate in that much of the grassland was likely in "conservation reserve" specifically because it was known to be vulnerable to erosion and/or flooding, which, in turn, means the lost soil moves directly into an adjacent stream channel.
Soil lost directly into stream channels makes nutrients available for transport to the Gulf Dead Zone. It also more readily plugs up culverts and shipping channels. Our Accidental Environmentalists did a bad thing, therefore, to push for elimination of the Federal conservation reserve program budget items (Democrats were right to resist those cuts).
Given the market dominance of Bt corn, the added corn acreage means evermore land covered with corn residuals containing trace amounts of Bt protein. Bt resistance in pest insects, to the extent that it occurs, may potentially be accelerated where corn residuals end up - including Mississippi River basin stream channels and even Gulf sediments. You Tea Heads want to believe this assertion is made up for politics, don't you? The science is in. See the post: Pesticidal Proteins (Bt) From GM Corn Plants Are Now Common In Midwest Streams
Next question: what happens to the converted farm land if ethanol subsidies indeed end and conservation reserve programs are not restored?