Bill McKibben on Grass-Fed Beef

A key cause of climate change
A key cause of climate change

It hardly seems fair to attack an article in which Bill McKibben, a tireless and effective advocate for much needed action on climate change, issues “a call for America to divest its heart and stomach from feedlot beef.” McKibben, like Michael Pollan, is attempting to define grass-fed beef as good, and factory farmed (corn-fed) beef as bad. From a political and ethical point of view, this isn’t a bad approach. In Colorado some years ago a ballot initiative restricting hog farms found the vegetarians and the cattle ranchers on the same side.

But does this make sense scientifically?  Cows naturally produce methane, a major greenhouse gas — that’s how they digest cellulose, their natural diet. When they are fed an unnatural diet that makes them sick (as on feedlots), they also emit less methane. Some scientists and even one study funded by the livestock industry reports that whatever its other merits, grass-fed beef is worse for climate change than feedlot beef for this reason. There are three specific questionable points in McKibben’s case to the contrary.

McKibben first of all states that the recent Livestock and Climate Change article in WorldWatch magazine (by Robert Goodland and Jeff Anhang) that found that 51 percent of all human-caused greenhouse gas emissions were due to livestock has been “discredited.” Indeed? And what is his source? He doesn’t give one; he just states it as a fact.

There have been some criticisms of Livestock and Climate Change, but none of them have stuck, and the authors responded to criticisms in the March/April 2010 issue of WorldWatch. The Atlantic Monthly and Macleans both recently cited the report matter-of-factly; the FAO is in an ongoing dialogue with the authors of the article, and Robert Goodland recently made an Earth Day presentation at Chapman University. The FAO and World Bank, at least, seem to regard it as quite credible. This is not to say that more evidence might come up later, but if I were making such a statement I would want to provide a further explanation or at least refer to something published so that people would know the reasons.

Secondly, McKibben raises the issue of naturally occurring ruminant animals: “nature had its own herds of hoofed ungulates. Big herds of big animals—perhaps 60 million bison ranging across North America . . . ” This widely-cited figure is almost certainly wrong. Dale Lott, who wrote a pretty authoritative book on the American Bison, said that the real figure is less than half of this — and he’s not talking about the actual numbers of bison, just about the theoretical carrying capacity of the land for bison in a good year under ideal circumstances. And even this ignores the roles of indigenous people in burning the prairie to maintain these herds, so it’s not clear how “natural” this was anyway.

Third, McKibben says that “recent preliminary research indicates that methane-loving bacteria in healthy soils will sequester more of the gas in a day than cows supported by the same area will emit in a year.” This would certainly be interesting news, but where is he getting this? Once again, he doesn’t say. A Google search on methane and bacteria turns up a 2007 Fox News story about extremophile bacteria that eat methane (“Methane-Eating Bacteria Could Save the World”), but nothing that would be widespread in grasslands. It’s not clear how soil bacteria would absorb methane belched into the air by cows, either, since methane is lighter than air.

We haven’t seen the last word on climate change and methane.  However, given the strong prima facie scientific evidence that grass-fed cattle are actually worse for climate change than corn-fed cattle, we should be much more careful in citing sources, so that we can at least tell where the author is coming from.