It was people.
It has always bothered me when people claim to be vegans for “environmental reasons” as the implication is that meat eaters are out to destroy the earth by remaining true to their carnivorous origins.
When I suspect the real reason many people are vegan is that they are following a fad and like to feel superior to their fellow dumb animals.
But we now have very clear evidence that farting cows and food production in general is not the main contributor to pollution. Cows are still out there farting away. Food production is arguably higher than ever given all there is for people to do now is eat.
It’s since the humans were kept indoors that the air has cleared.
How do vegans rationalise what most non-vegans knew all along? That it’s human traffic - including vegans - causing the problem.