You can't break down the environmental impact of foods by saying "meat bad, veg good" - it's far more nuanced than that. Most of the environmental impact of any food comes from clearing land for monoculture, subsidized water supply systems, pesticides and herbicides to keep competing plants at bay, labor intensive harvesting, transportation, storage and the distribution supply chain. I could grow my own lettuce (best), buy it from a local farmer (good) or buy it from a supermarket (worst) - how it gets to your table is by far the biggest driver of environmental impact, not the food itself.

Sure, we should be eating less meat. But it's not a panacea, we must address the systemic problems of industrial agriculture that makes veganism possible.

Vegetarianism seems like it should be enough - if your argument is ecological.

Do you have a source on that? A source which takes into account "milk cows" being slaughtered and eaten after max. 4 years too? Accounting for the fact the cows only produce milk when having baby cows and some of these being male?

I am highly sceptical cutting meat is enough. Animal based protein, and energy is just inherently wasteful since 3/4 of intake energy is radiated away as body heat. (Yes, there is this super small niche of grass land unsuitable for humans feeding agriculture.)

I am not sure about the thermodynamics and ecology of fish in general, but I think eating predatory fish is an ecological disaster regardless of the carbon footprint.

Just to make sure, I don't think you have to quit all animal products for a sustainable future. If people go 95% plant based calorie-wise that's probably enough. Celebrate a steak once a month, commit to that, pay the real price for that!

"GHG emissions in kilograms of carbon dioxide equivalents per day (kgCO2e/day) were 7.19 (7.16, 7.22) for high meat-eaters ( > = 100 g/d), 5.63 (5.61, 5.65) for medium meat-eaters (50-99 g/d), 4.67 (4.65, 4.70) for low meat-eaters ( < 50 g/d), 3.91 (3.88, 3.94) for fish-eaters, 3.81 (3.79, 3.83) for vegetarians and 2.89 (2.83, 2.94) for vegans"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4372775/

I don't know what reduction is enough.

I think this study does not address my point and includes dairy products as their partial footprint of growing cow. The problem is: no meat, no milk.

The low footprint of vegetarianism only works as long as there are meat eaters eating the "milk cows". If everyone stopped eating meat, the dead cows would end up on the vegetarian's bill. I hope this doesn't sound stupid and you get my twist :)

My wife has recently cut out a lot of dairy products and tried to replace them with vegan alternatives. The problem is most of the alternatives you can buy from the supermarket are made from coconut oil, soybeans, or some kind of exotic nut - which typically aren't grown here in Europe. I'm not sure if these are any better than dairy products, especially if you take into account conversion of rain forests (in places with less stringent regulations than the West) to agricultural land to grow these crops.

This "argument" gets repeated over and over...

Every plant based product is better than their equivalent animal (warm-blooded mamals) product. Animals radiate away about 3/4 of the energy they consume. This means generally speaking land use for every x amount of animal produce, you'd only need 1/4 of the land to feed humans on plant produce. Of course some plant are worse than others nutritionally, but I think the overall idea of energy waste by warm-bodied animals is pretty self-evident. Soy is a pretty high quality protein mix and overall, it's questionable if overfeeding on easy proteins is a good idea health wise, e.g. see methionine, IGF-1 and cancer risk.

Fun fact: Almost all soy for human consumption in Europe is actually grown in Europe. The rainforest killing soy is grown to feed cows. See above...

Oh look it's even worse: only about 10% of intake energy is fixated (plant matter -> meat) in the next trophic level.

https://en.m.wikipedia.org/wiki/Ecological_efficiency

Wikipedia says ATP generation alone loses 60% of energy regardless if ecto- or endothermal organism. ATP is the energy curency of life. So 60% of energy lost, before any synthesis, signaling, membrane transport, ... even happened.

I don't disagree that eating plants is more efficient than eating animal products, but what I'd like to know is how much it costs to transport these products.

Is coconut oil grown and processed in Thailand, then flown to Europe and transported by truck another few thousand miles, still better than butter made from cows milk that are raised 20km away?

I doubt the transportation has a huge impact, but either way it's an issue of its own. You don't have to eat vegan products grown across the globe. Bringing this up is as relevant as talking about the footprint of the clothes you wear while eating. Btw. the soy grown in the Amazonian ex-rainforest to feed cows, isn't magically appearing on American farms either.