Agriculture is not responsible for the bulk of worldwide greenhouse gas emissions; that honor goes to more fossil-fuel intensive activities like transportation and generating electricity. Even still, greenhouse gas emissions from global agriculture are climbing by 1 percent a year.

Humans did once upon a time live without HDTVs and Hummers—we could do so again, at least in theory—but people will always have to eat. This makes reducing agricultural emissions particularly difficult. Researchers in the UK have reported that an approach called "land sparing" farming could offset the emissions coming from agriculture by sequestering carbon.

Land sparing increases the efficiency of existing farming practices, allowing more food to be produced on less land. The surplus farmland is then allowed to revert to a “natural” habitat. It all sounds sensible, and the paper led to a number of news articles earlier this month.

However, the actual paper leaves a lot of blanks to be filled in by technological solutions that don't actually exist yet.

The authors' models, for example, have some pretty hefty caveats. They note that “As yields increase, the area of farmland required for a given level of production declines, allowing land to be spared.” True, but they don't mention how we get yields to increase; rather, they helpfully point out that “A key issue, therefore, is identifying the mechanisms that could contribute to this outcome.” Naturally, especially as food demand is also projected to increase.

The authors also rely on as yet undefined future developments in the field of animal husbandry to reduce emissions. “A large proportion of projected upper-bound mitigation arises owing to assumed growth in livestock productivity,” they write. “Our upper-bound livestock productivity gains assume that technological advancements lead to continued genetic gains through breeding, coupled with improved livestock health and nutrition.”

But it's not just the cows that would have to change. Cutting meat out of our diets and trying to minimize food waste can also alleviate the growth of emissions, they report. They suggest that a tax on meat might do the trick.

The takeaway from this paper is that using land for forests that store carbon instead of growing crops and grazing cattle can reduce greenhouse gas emissions, or at least slow the growth of greenhouse gas emissions. Provided, that is, that someone, somewhere, somehow figures out how to actually grow enough food on the reduced farmland.

Nature Climate Change, 2015. DOI: 10.1038/nclimate2910 (About DOIs).