This is the June 12th entry from my "Living Green" page-a-day calendar (email version so I'm not wasting paper :-)
"A steak might be an American institution, but it comes with a side of environmental costs. Central and South American forests are being cut or burned down to provide pasture. Effluent from feedlots pollutes land and waters, and each cow produces 300 liters of methane—a greenhouse gas—every day. Consider reducing the amount of meat you eat; while the cows aren’t problematic in and of themselves, modern mass-farming methods take a toll. "
We tend not to eat a lot of meat in our home anyways, but in addition to the health benefits this is yet another reason to cut back on red meat.