This isn't just about producing meat. Land has to be cleared for new fields to grow produce as well. This is more of an effect of people being disconnected from their food. It wasn't that long ago when most people grew atleast some of their food on their own land. Within a community almost, if not all, of the people's food was grown. It was consumed fresh and at its peak, supplying the best nutrients as well as energy.
Now few people, atleast in the US, grow any food at home. It isn't that they don't have the means, it is that they just don't. I drive around and see acres and acres of nicely mowed lawns. There are houses sitting on atleast 1 acre, though many times a lot more than that, with nothing but grass on them. What do they do with that grass? They just mow it. What a waste! If they wanted just grass the least they could do would be to put a cow or goat (or a few) out there to eat the grass and keep the 'lawn' trimmed and neat. Then at the end of the season they could have some meat, or have milk most of the year. A few animals do not require a lot of space.
If they wanted to, they could be growing atleast some of their food on a small patch of that, or all of it. In the time they spent mowing their yards they could have put time in growing some of their food. This would not only reduce the need to destroy forests for new mega fields, it would also provide them with fresher, healthier food and create a more stable and sustainable food supply.
Again the only reason we have these problems is because of industrial agriculture. Farming spread out in the form of small farms is much more environmentally friendly. Large concentrated mono 'crop' operations cause a lot of problems because they are not natural.
the less people that eat meat, the less of a need for industrialized agriculture. Cows cause pollution.
"Methane, which is 23 times more potent than carbon dioxide as a contributor to global warming, is produced daily by cows. In fact, agriculture generates about 14 percent of the greenhouse gases today -- including two-thirds of all ammonia -- from cows. Even though other grazing animals also expel greenhouse gases, statistics suggest that cows produce 26 to 53 gallons (and some say up to 132 gallons) of methane every day -- the same amount of pollution emitted by a car in a day. And it's only going to worsen: The U.S. Food and Agriculture Organization predicts a 60 percent increase in agricultural methane output by 2030"
http://curiosity.discovery.com/question/cows-cause-pollution-than-cars
"Nothing will benefit human health and increase chances for survival of life on Earth as much as the evolution to a vegetarian diet." -Albert Einstein
btw, it's nice to see you here again WITW