Comma and conjunctions. Is the sentence truly an idependent one?

Question

I am correcting a text for a friend. She wrote:

You can find biodiversity in wild meadows, but these areas decrease by seven percent annually.

A comma should be used if there are 2 independent clauses. To me, "these areas..." is not truly independent. If I read this on its own I would not know "these areas" actually are, right? Therefore there shouldn't be a comma?!

I encountered the same problem when correcting a longer text about a certain topic. In a paragraph, some of the sentences could not be really understood if you had not read the preceding ones first although they didn't use "this" or "these". I don´t know if these sentences should be called independent at all?

Answer 1

There are two independent clauses in the example. The fact that the second clause uses a pronoun that refers to the first doesn't mean that they are grammatically dependent.

A sentence "This is mine." is a complete sentence, even if I don't tell you what I am talking about.

You don't need to know what "these areas" refers to. Grammatically independence just means that the clause has a subject and a finite verb. You could say the clauses are semantically dependent, but grammatically independent.