This isn't about the way animals are treated, nor is it about reducing heart disease. For the sake of the climate alone, we -- as a culture -- need to eat half as many burgers, and half as much bacon.

According to a recent study from Davidson, this controversial dietary shift is crucial if we want to get serious about reducing emissions of nitrous oxide (N2O), a potent greenhouse gas.

We've long known that eating animals (who eat grains) requires a great deal more agricultural production than eating those grains ourselves. And since farming involves fertilizers and animal manure -- two factors that have recently been pinpointed as major contributors of atmospheric N20 -- we need to use much less of them. Oh, and while we're at it, the way we farm also has to change, to the tune of 50 percent fewer N2O emissions.