Inefficient land and resource use
Land degradation
Loss of biodiversity
Soil erosion
In the US, most of the land used for grazing is already insufficient for farming most crops. You take cows and such off of them, you're left with near-useless land.
Chemical runoff from pesticides and fertilizers
Not exclusive to livestock and their feed, feels weird to attribute it to just them.
Widely-available meat in the Western world is a Pandora's Box; it's just not going away. It's better to find ways to make it more efficient than to go all pissed-off-vegan and want to ban meat everywhere in favor of ultra-processed replacement monstrosities. You'll win more people to your side too.
Furthermore, attacking the end-consumer does absolutely nothing. It's like banning plastic bags/straws, It just makes liberal lawmakers feel good about themselves. You want to really change our diets? Go after the billions in subsidies handed out to farmers for growing corn/soybeans/dairy and such in order to stay competitive against cheaper products overseas. Good luck.