York's first claim, that my essay overstated the climate benefits of pasture-based farming, misses the mark in several ways. She emphasizes that methane, especially from enteric emissions (related to ruminants' digestion), rather than CO2 or nitrous oxides, is the real global warming threat related to meat. I agree that methane is the gas of greatest concern. However, as my op-ed notes, there are viable remedies. University studies have demonstrated that good cattle nutrition and management can substantially reduce such emissions. In addition to the research cited in the essay, consider the following: a study published in the Canadian Journal of Animal Science showed that access to high-quality pasture reduced cattle methane emissions by as much as 50 percent and that cattle grazing on pastures containing legumes and grass produced 25 percent lower methane emissions than cattle grazing on pastures without legumes. Legumes, such as clover and vetch, can be seeded in grazed pastures. In other words, enteric methane is a solvable problem.
There's another thing about enteric methane: it's been around for eons. Logically, climate change policy should focus on things that are in fact changing, especially those caused by human activity that can be altered. The original draft of my Times essay contained the following paragraph, which we needed to cut due to space constraints:
Prior to European colonization of North America, enormous herds of large ruminant mammals covered the continent, including millions of deer, an estimated 10 million elk and somewhere between 30 and 75 million bison. "The moving multitude...darkened the whole plains," Lewis and Clark wrote of bison in 1806. The total number of large ruminants was surely greater than the 40 million mature breeding beef cows and dairy cows in the United States today.
Additionally, as the op-ed also points out, rice fields cause as much as one third of the world's human generated methane. So it's illogical, or at the least skewed, to single out meat.
A related point I emphasize in my op-ed but York ignores in her response is that a food's environmental impact should be considered holistically. It's important to consider grazing's significant environmental benefits. For one thing, pastures have been shown to sequester substantial amounts of carbon, much more than cropland. A mountain of studies have shown that pasture is by far the most ecologically sound method of producing food. Compared to cropland, pastures have much less soil erosion and cause much less water pollution. As the op-ed mentioned, they can also be excellent ways to maintain natural ecosystems and biodiversity. Moreover, the rumen's role in food production is nothing short of miraculous. As Cornell University professor David Pimentel wrote in Food, Energy and Society, ruminants can effectively make use of marginal land that is otherwise unsuitable for food production;they are intermediaries between naturally occurring, inedible cellulosic vegetation and human beings. In other words, by grazing on forage that humans cannot digest--thanks to their rumens, the very cause of those enteric emissions--grazing animals make efficient use of natural resources.