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The problem with the assertion that cattle methane has had a meaningful impact is that it's not measured against any historical control. We have a roughly 50-60 million year period to compare against where mammals have been the dominant kingdom of animals on planet earth [1]. Their digestive systems have not meaningfully changed. Livestock have merely supplanted biomass that would otherwise be wild biomass, producing methane just the same (though perhaps distributed over a more diverse spectrum of species). Domesticated cattle occupy land that was occupied by wild ruminants long before it was fenced in. In the absence of monocrop agriculture and human dwellings, hundreds of millions of more acres would be occupied by ruminant mammals. The Great Plains, where we today grow massive amounts of corn, wheat and soybeans, were occupied by massive quantities of bison, elk, and deer. And before the mass extinctions of the Late Pleistocene, the earth was massively occupied by wooly mammoths, giant ground sloths, giant bison, muskox, shrub ox, stag moose, stout legged llamas, etc etc [2]. The Eurasian biomass of wooly mammoths alone was more than the global biomass of all domesticated cattle alive today [3] (assuming 200 million mammoths 50K YA in Eurasia and 1 billion global cattle population today, with mammoths averaging 10x more mass than cows). It might be the case that human activity actually reduced the amount of methane produced globally by four-legged ungulates (although surely we've more than made up for the difference from mining and drilling). [1] https://www.science.org/doi/10.1126/sciadv.adn6842?utm_campa...
[2] https://en.wikipedia.org/wiki/Late_Pleistocene_extinctions
[3] https://www.researchgate.net/figure/Estimated-Number-of-Wool... EDIT: On further review, I found a study that makes the attempt to estimate what pre-European U.S. settlement methane production attributed to ruminants was and estimates it to be 86% of what modern day livestock and wild ruminant methane production, underscoring my point (livestock ruminants merely supplanted wild ruminants): https://pubmed.ncbi.nlm.nih.gov/22178852/ |