I'm not a native English speaker, so help me out here. Is not the sentence "What a beautiful nature" incorrect, in the same way as "What a dreadful traffic"? I thought the "a" was removed in English when speaking about these sort of uncountable nouns. Or would you argue that "nature" is in fact countable?
Even though "what beautiful nature" sounds strange to a lot of native english speakers, as someone who has spent a lot of time studying Norwegian and now Swedish, I think that sentence sounds fine, and is something you would likely hear from a Norwegian speaking english. Can't say for sure about a Swede.
I think it is important to note that Norwegians and I'm guessing Swedes have a slightly different connotation for the English word "nature" than Americans do.
For example, if you told someone in Scandinavia you were visiting and "want to see all the beautiful nature," I don't think people would think twice about it.
I'm not sure if it makes it a "correct" sentence in english or not, but that's my two cents.