As per title, but see the link here: https://www.theguardian.com/uk-news/2018/oct/23/welsh-slate-quarries-gwyned...
The proposed area includes the Dinorwig quarry. UNESCO sites are "intended for practical conservation for posterity, which otherwise would be subject to risk from human or animal trespassing, unmonitored/uncontrolled/unrestricted access, or threat from local administrative negligence". Given that climbing in the quarries is formally not allowed but quietly ignored, how would this play out?
Furthermore, North Wales is already pretty busy. Does it really need an increased tourist load often associated with UNESCO status?
(n.b. decisions wouldn't be made until 2021)