Someone once predicted that if there were no tobacco on the earth , there would be no conflicts in the world. This would seem to be an exaggeration, but it would also seem the harm of tobacco is underestimated. At least I think that's what you're trying to say. Start sentences with a capital letter and leave a space after a full stop. Moreover, watch your spelling. All in all, it was pretty awful.

I don't smoke so I wouldn't care if there was no tobacco at all. so it's wrong.

if on the the earth was not tobacco there would not be reason to conflicts. The problem would be if sb had tobacco and rest of world would not have :D i am not sure if you ask if the hypothesis is right or sentence :D so as for sentence it should be "if there was not tobacco on the earth, there would be conflicts in the world. " - it is 2th conditional sentence (if sb was ... it would be ...) ;)

if on the the earth was not tobacco there would not be reason to conflicts. The problem would be if sb had tobacco and rest of world would not have :D i am not sure if you ask if the hypothesis is right or sentence :D so as for sentence it should be "if there was not tobacco on the earth, there would be conflicts in the world. " - it is 2th conditional sentence (if sb was ... it would be ...) ;)

I don't see a link between tobacco on the earth and conflicts in the world, so I would say this is an exaggeration. Two hundred years ago, however, tobacco was used as money in early America. Even traveling preachers were paid in tobacco, because they could use it to buy other things they need.