A letter in Science last week from William Laurance of the Smithsonian Tropical Research Institute lays out a piece of the argument I’d not heard regarding the extent to which ethanol as fuel reduces, or doesn’t reduce, carbon emissions. The ethanol push in this country is causing U.S. farmers to shift from soy to corn. That’s triggered a rise in global soy prices, Laurance argues, which is leading to greater deforestation in the Amazon to grow more soy:

In a globalized world, the impacts of local decisions about crop preferences can have far-reaching implications. As illustrated by an apparent “corn connection” to Amazonian deforestation, the environmental benefits of corn-based biofuel might be considerably reduced when its full and indirect costs are considered.