The second and third planks of the
Deep Ecology platform are:
2. Richness and diversity of life-forms contribute to the realization of these values and are also values in themselves.
3. Humans have no right to reduce this richness and diversity except to satisfy vital needs.
That says to me that we are allowed to reduce diversity to some extent through agriculture, but only in the pursuit of vital needs, like food. I say "biofuels for everyone" is not a vital need. Others' mileage may vary.
Deep Ecologists tend to be the most philosophically uncompromising SOBs in the green movement. If they've decided that some agriculture is morally defensible, I'm good to go. But dammit, making enough ethanol so everybody can just keep on truckin' like back when there was still oil does not meet my definition of a vital need.