Wrt:  Levyubg taxes according to food-chain ranking so that
   products with the worst environmental impact cost the most...
  If one chooses to eat high-impact food, one should pay the full costs of
such a choice,"

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To be accurate, the foods that should be taxed most should be foods that
take a lot of processing (energy/fuel) to be made EDIBLE for humans.  Tops
on the list should be legumes, grains, sugar and products made from them.
It takes a HUGE amount of energy to turn raw soy beans into soy milk, tofu,
soy dogs, soy burgers, soy candy bars; to turn wheat berries into vegetarian
"wheat meat," puffed cold cereals, etc.

My husband read a book many years ago on food processing and the amount of
energy it took to process and can corn and make breads and all that.  I
can't recall the name of the book, BUT I do recall that it took more
k/calories of energy to process most conventional canned, boxed, bottled
foods than the foods actually yielded.  Soda pop and all other things that
don't provide nutrients should be taxed to the MAX!!

Grass fed animals, including pasture raised poultry and birds/eggs, would be
ideal then.  We should move our agriculture economy in that direction.  Btw:
If bison and lamb were raised more than beef cattle, that'd be more
ecological as well.  THese animals are better suited to dry lands, more
weather hearty, require less water, no pampering, etc.

Also, our grain-based agriculture supports an unnaturally large population
which puts great strain on the earth.

 Rachel