It's not the cow, it's the HOW
sustainabledish.com/its-not-the-cow-its-the-how-new-study-shows-grass-fed-beef-can-be-a-carbon-sink/
Grassfed pastured ruminants are a net benefit for the environment, they sequester carbon (tons per acre per year), they encourage deep root structures in the grass, which hold nutrients and water, minimising runoff and flooding. They can help reverse desertification... see Allan Savory's TED talk.
www.ted.com/talks/allan_savory_how_to_green_the_world_s_deserts_and_reverse_climate_change?language=en
The key thing is that they do not displace nature and other creatures, like what happens with tillage agriculture. Agriculture is ecocide. Basically, you take a piece of land, you clear every living thing off it, whether it was a forest or a prairie, down to the microscopic bugs in the soil. You spray it with herbicides, fungicides, insecticides, fossil fuel fertiliser. All of those have huge ecological impacts. Even just the act of breaking the soil with the plough puts tons of carbon into the atmosphere.
Obviously, if you first grow grains/soy and feed them to cattle, it amplifies the already bad effects of agriculture, you also get very sick animals who are not eating their natural diet and require large amounts of veterinary medicines and antibiotics. Grain fed animals are the farters and belchers, grassfed ones are a net negative effect on carbon levels, ie they help sequester more carbon into the soil than they emit.
Compare that with the management of livestock and nature at the Knepp Estate in Sussex. Wildlife is flourishing there. Cranes have recently returned. Read this article and Wilding by Isabella Tree
www.theguardian.com/environment/2018/jun/15/the-magical-wilderness-farm-raising-cows-among-the-weeds-at-knepp
Also read the Vegetarian Myth by Lierre Keith, it turned me from an annoying radical vegan, to an ethical, deep ecological, grassfed meat omnivore.
www.amazon.co.uk/Vegetarian-Myth-Lierre-Keith/dp/1604860804/?tag=mumsnetforu03-21