Tomatoes taste good, but how good are they for the planet?

RODALE NEWS, EMMAUS, PA—It's no secret that factory farms are heinous, polluting messes. Farm operators inject their animals with antibiotics and growth hormones that, in the form of animal waste, run off to nearby rivers and ponds. Growing all the grain used to feed these animals requires thousands of pounds of petroleum-based fertilizers and pesticides that generate greenhouse gases and create ozone. And all that meat is bad for our health, leading to chronic heart problems and even vision loss.

But is eating a vegetarian, or mostly vegetarian, diet better for the environment? This week, the Environmental Working Group (EWG) tried to answer that question with a new report on the environmental impact of farming.

The group's analysis of beef, chicken, pork, vegetable, and fish production concluded that beef produces serious amounts of climate-changing greenhouse gases, while vegetables do not. But it's not just beef that's heating up the plant. Fish production and cheese making are huge contributors of greenhouse gases, with farmed salmon and canned tuna emitting more than some forms of meat, and cheese generating more emissions than pork. (If you'd like to read the full report, view it on EWG's website).

For those who choose to eat meat, the report's authors stress that grass-fed livestock is the way to go (in agreement with a recent Department of Agriculture study finding that grass-fed cows produce fewer greenhouse-gas emissions). Not just because pastured animals are less polluting, but also because their meat is a healthier choice. Studies have found grass-fed beef has lower levels of saturated fat, higher levels of healthy omega-3 fatty acids, and more vitamin E, beta-carotene, and B vitamins.

Here are five other interesting facts the report revealed about farming and the environment:

#1: Lamb tops the list. In terms of greenhouse-gas emissions, lamb was the worst, generating 50 percent more emissions of greenhouse gases than beef production, and six times more greenhouse gases than producing chicken (which generated the lowest greenhouse-gas emissions of all the meat production analyzed). Sheep, like cattle, are ruminant animals that generate a lot of methane (a delicate way of saying they pass a lot of gas). And methane is a potent greenhouse gas—25 times more damaging than carbon dioxide. Lambs also produce less edible meat per pound of live weight than cattle do. It takes a lot of greenhouse-gas-emitting fertilizers and pesticides to raise the food lambs eat, compared to the small amount of meat a farmer can harvest from them.