your link is new to me, so i dug through it a bit, checked some references, and i've decided the methodology is bad, and the authors either know this or they should have known this. the primary source for the LCA comparisons says, in plain english, in the introduction that LCA's should not be used for comparisons due to a lack of control for the data gathering procedures. the actual paper's purpose was to, i shit you not, ignore this guidance, average every datapoint they could find for any food type, and then stock them together in one paper.... to let you compare LCAs. this is shoddy work.
i didn't bother to go digging into the tertiary sources on which your link relies, but i will say i did some of the reading into the sources for other papers on the impacts of animal agriculture, and i have yet to find any investigation that doesn't attribute to livestock all of the impacts of everything in their diet. that seems reasonable: if a cow eats it, then it should be counted. but that falls apart under scrutiny. my primary example is that, in the united states, many cattle are fed cottonseed. cottonis not a food crop, though. it's a textile. the cottonseed is a byproduct, and whether we feed it to cattle or press it for oil, any such use is actually reclaiming resources. how should that be counted? it's not as though cottonseed is an essential part of cattle diets, it's only through the happenstance of its availability and relative price point that it's in there at all.
and this just points at a larger problem: everything in our agricultural sector is so intertwined and interdependent that the impact of anything is a mercurial notion, that changes on a seasonal basis dependent on the weather, technology, and people's feelings.
i don't believe beef can't be raised sustainably (which is to say, indefinitely on a given plot of land, given sufficient sun and rainfall). i'm open to data about this, but cattle were among the first domesticated animals, and we've seen all kinds of climate change since then, so cattle can't be the problem in-and-of themselves.
