Look I'm not putting up an argument where neither of us have the data to look at this factually, but I don't think we had any problems in the pre industrial revolution era.
My point is - The focus should be on optimizing the sources that contribute the most to these emissions.
The article mentions this could reduce Australias ghg emissions by 10%, figures I've found for the UK suggest 3%. That's a massive cut no matter how you cut it, and shouldn't be ignored.
You cant just say cows were domesticated before the industrial revolution, ergo cows are ok, and shouldn't be part of the solution. Animal husbandry has changed massively in the past 2/300 years, you are comparing apples and oranges.
My 2 orders of magnitude guess is conservative. Population has increased by well over one order of magnitude since the industrial revolution. Per capita meat/dairy consumption accounts for the rest.
My point is - The focus should be on optimizing the sources that contribute the most to these emissions.