For environmentalists, the most emotionally damning critique of biofuels is the threat energy crop cultivation poses to rain forests. The thought of fueling one's SUV with biodiesel made from palm oil harvested from plantations cut from virgin orangutan habitat is legitimately obscene. Brazil, however, has so far mostly insulated itself from such criticism by pointing out the irrefutable fact that the vast majority of its sugar-cane plantations are located well south of the Amazon jungle.

But the global economy works in more insidious ways, as reported in a superb piece published today on Mongabay.com.

Here's the basic equation. The demand for ethanol has encouraged farmers in the U.S. to vastly increase the acreage of farmland devoted to corn this year. This has resulted in a concurrent decline in soybean production, and a rise in soybean prices. Brazil is responding to this incentive by dramatically increasing its production of soy. Most of these new soy plantations are also not being carved out of the rain forest, but instead, are displacing small farmers and cattle ranchers who then start impinging on the virgin forest frontier.

The consequences of this butterfly flaps its wings in an Iowa corn field and a cattle farmer swings an ax at the Amazon jungle have important implications for the movement to certify biodiesel as environmentally sustainable. What good does it do the world if a soybean or sugar-cane plantation is itself certified as innocent, when the downstream effects result in the same problem the certification program is attempting to avoid?