Can smoking weed hurt a mans sperm?

My SO smokes weed everyday and has been for years. I'm worried about when we try to have a baby if he'll be able to give me one naturally. I would really rather not have to do invetro or artificial insemination. He doesn't want to stop smoking but says he will when we start ttc if necessary. Our friend had a baby and he smokes all the time. So is this true or not?