The Vegan Thread

I don't have specific papers to hand and I frankly can't be bothered to trawl through introductions to find the right ones, but it's perhaps worth pointing out that it's better for the environment to give up cheese/milk/yoghurt than it is to give up chicken/eggs. Beef is of course by far the worst source of protein by a long way.

This data is just grouped into "dairy" rather than splitting between cheese, milk and yoghurt but illustrates the point

https://ourworldindata.org/grapher/greenhouse-gas-emissions-per-gram-of-protein-by-food-type

Edit: I also found this random article:

...rank different protein sources in terms of their life-cycle greenhouse gas emissions per four-ounce serving. Beef, as you’d expect, is bad — No. 2 on the list in terms of climate impact, surpassed only by lamb. But the No. 3 offender is cheese, ranking worse than pork and chicken ounce for ounce, and substantially worse than other dairy products like milk and yogurt.

What makes cheese so bad? “Cheese has a high carbon footprint because it takes a lot of milk to produce a pound of cheese — 10 pounds of milk, on average, go into producing a pound of hard cheese,” says report author Kari Hamerschlag, senior analyst at EWG. “You’re producing the milk from a dairy cow that is emitting large quantities of methane, which has a global-warming impact 25 times higher than carbon. And then you have the methane and nitrous oxide that are also generated from the cow’s manure. And then all of the grains that go into feeding the cows, which range from corn to alfalfa and other forage, and there’s a footprint associated with that.”

...

Are greenhouse gas emissions lower for cheeses made from goat or sheep milk? Nope. Finnish researchers reported in 2008 that goat cheeses are roughly similar to cow cheeses in terms of emissions, while sheep cheeses are worse because sheep emit more methane per unit of milk produced.

Hard cheeses take a lot of milk (10:1 milk to cheese by weight), so you will want to avoid those. Soft cheese takes less milk. I don't know about yoghurt but it doesn't take a lot of time to make so I expect that the ratio of milk to yoghurt is much lower (near enough 1:1 perhaps) as evaporation/shrinkage/whatever isn't really a significant part of the production process.

Ultimately the best thing to do would probably be to eat legumes, grains, nuts, etc. first, then eggs, chicken, pork, milk and yoghurt, soft cheese, hard cheese, beef in order of decreasing frequency, sourcing things locally as often as you can. I feel like the climate impact of eggs from locally-kept chickens is going to be very minimal and the ethical concerns aren't too great if the chickens are healthy and well-kept and effectively treated like pets. To the point where they're probably better for the environment than beans/rice that have been transported by plane.

Edit: forgot about sea food. Absolutely no idea where that falls on the scale but if I had to make a complete guess I would say that local line-caught fish is probably still better than pork, cheese, beef etc. though it raises questions about ethics. Other seafood is probably the same.