Sentence punctuation 2: with more than one independent clause

The table below shows some ways in which ideas may be linked  together in a sentence which contains more than one independent clause. These clauses are of equal importance to each other and could stand alone in separate clauses. Common ways of linking independent clauses in one sentence are to use punctuation markers or words like "but", "and", "so" and "or".

If you use a logical marker in these kinds of sentences, you need to use between-sentence markers, because the clauses are all independent, and therefore equivalent to a sentence.

Some people worry about the future of the planet

 : many species are disappearing at an alarming rate
colon (:) shows reason for people's worry
clause #1: subject "some people", verb "worry"
clause #2: subject "many species", verb "are disappearing"
Some people are often rather unconcerned about other environmental issues ; they worry about the issue of biodiversity.
semicolon(;) shows contrast between people's lack of concern about some issues and their concern about biodiversity
clause #1: subject "some people", verb "are unconcerned"
clause #2: subject "they", verb "worry"
Some people are often rather unconcerned about other environmental issues (,) but they worry about the issue of biodiversity.
2 independent clauses linked by contrast marker "but"
comma before "but" optional
Some people are often rather unconcerned about other environmental issues ; they worry, however, about the issue of biodiversity.
semi-colon (;) shows the ideas in the 2 independent clauses are equally important individually, but closely connected - in this case by contrast
contrast between people's lack of concern about some issues and their concern about biodiversity marked by contrast marker "however"
comma before and after "however" because marker is not in initial position