[wolfgang]

Originally Posted by vlizz

The only problem with your reasoning is that trees are a renewable resource when re-forestation is utilized, and fossil fuels are not. As long as trees are replanted, the net carbon balance is unchanged. Even if we all become vegetarians, growing populations are going to demand more food. Instead of growing crops to feed the animals, you are going to grow crops to feed yourself.

So clear cutting for cows (no re-forestation) is the same as having a growing population to feed? The comparision is between land use for not eating cows versus eating cows. You can't throw population in to that comparison because if eating cows uses more land than not eating cows, more people would still mean less land to not eat cows.

Contrary to popular belief, livestock is an efficient way to harvest solar energy when managed correctly. Cattle can be used on marginal land where crops cannot be grown well to turn solar energy in the form of grasses into a form we humans can digest (meat). For more on this read The Omnivore's Dilemma by Michael Pollen. The problem is that in the present day, most cattle are fed corn or other calorie intense grains in order to produce meat.

Free range cows? How to change that industry at this point - they are after yield. If free range cows would be more efficient, why hasn't the industry gone that way?
LEAD digital library: Livestock’s long shadow - Environmental issues and options

This is much less efficient than using marginal land grasses and requires fertile soils to produce the grains. Becoming vegetarian is not going to stop deforestation or global warming.

Not eating cows will slow deforestation by a lot.

How will it decrease the world's need for food and land to produce that food on?

That is not the question. The question is: would not eating cows be far less impact than eating them? And maybe be managable.

This is even better:
Spirulina's Environmental Advantages