The single greatest source of greenhouse gasses AND of polution in general is... (Xpost from enviro)

[Scootaloo]

2. It's a question of layers

We destroy forests to make way not just for the animals, but also the food we give them. Forests are very carbon-dense, they sequester a lot of the stuff away. when we tear them down, we burn most of the matter, and what's left rapidly rots. Both release carbon. We then replace that growrth with cereals, soya, and the like - none of which are particularly carbon-dense. we then feed this stuff to cattle and pigs, bot hof which are CO2 and methane factories (as are all animals, really). And we have immense numbers of these things. We then have toi power the apparatus to caretake for these animals, then kill them, then preserve them, then ship them, then keep preserving them, on and on down the line.

of course, we could take the cows out. Take them completely out. everyone goes vegan. What happens to global warming? it keeps on keeping on, because the cows are just one corner of the problem. Maybe as a single, individual cause they are very large. But as a part of the whole, they're ultimately negligible.

There is no one "magic button." Nothing is ever so simple.