Researchers have linked dietary data from over 55,000 individuals with data on the environmental impacts of the foods they eat. The team, from the Livestock, Environment and People (LEAP) project at the University of Oxford, found that the dietary impacts of vegans were around a third of those of high meat eaters. They also saw a 30% difference between high- and low-meat diets for most of the measures of environmental harm.
Yes I am on the same page mostly but this paper does not actually cover the impact of a vegan diet nor all the situations that can arise. There needs to be a lot more work on the large scale impacts of many diets to really get the best dialed in. I think the huge factory farms are the main issue, but what is not mentioned are the huge factory farms are not all raising meat and that depending on location the transportation impact is larger then the damage done when producing (think of bananas for example). I have worked on large cash cropping operations (canola, soy and some corn) and was frankly shocked at how little thought was put into any sort of environmental impact.
In contrast I have a neighbor who turned an old abandoned property (less then 5 acres) into a small homestead for their family. They have some of trouble growing much of anything on that land (they had to bring in soil and build cold frames), but they have no issues grazing with their goats, sheep, chickens and one cow (whose name is Daisy and was raised like a dog). They seem to have drastically reduced the environmental impact of the family and may have even reduced below say a vegan living in a large metro center, but this would not work for most of the worlds population and is not scale able. I guess I just think more work has to be done to figure this out.