De fromme muslimers stofmisbrug fører til vandmangel:

“Yemeni citizens have lived on scarce water supplies for thousands of years but the problem has been exacerbated by widespread production of the local drug of choice, qat, which consumes up to 40 per cent of water. About 70 per cent of Yemeni men chew the leaves each day, and bushy qat trees are often the only spots of green in the dry landscape.”

http://www.timesonline.co.uk/tol/news/environment/article6883051.ece