There are intensive methods of agriculture involved in producing tobacco; the biggest environmental damage issue apparent is ironically one of the worst side-effects the raising of massive cattle herds bred for the meat industry creates: deforestation.
That said, the latter is inherent in farming many, many other raw products such as soya, which are often sown on land formally used for ranching in the Amazon, and make the land all but useless at recovering in the aftermath. As a whole, we humans are simply awful at creating big business with minimal impact on the planet's lungs! -_-
Incidentally I quit smoking cold turkey at the beginning of July. It was actually one of the principle factors that made up my mind when I considered going vegan again. I felt I owed my body something positive (not that I don't still stuff my face with popcorn!) I won't tell you to quit because I sure as hell never listened when others told me the same, but I will say that taking the leap, when you do... it's actually ok over here: it is doable.
