Correct usage of en-dash/em-dash in this example

Question

Just when you thought the world had suffered enough in 2017, Mother Nature decided it hadn’t – brewing from 25 August, Hurricane Harvey, a Category 4 hurricane, struck the southern area of the United States, killing 90 civilians and striking up an astonishingly high damage cost of $198.6 billion – despite their growing prosperity and developments in building more withstanding infrastructure, the hurricane was the costliest natural disaster in United States history.

Is this correct usage of the en-dash connecting the sentences within the paragraph this way: informally? It's confusing to tell where the new sentences begin. It's from an informal source though. Capital letters are a rule are they not when connecting two independent sentences with a dash?

What the difference between using an en-dash or an em-dash in this type of usage.

Answer 1

There is only a single sentence in your passage, not several that have been joined together by dashes.

From a purely syntactical point of view, it's a connection of three independent clauses within the same very long sentence.

There is also no guidance I know of that says to use a capital letter after a dash—unless the dash actually does terminate a sentence, such as in the case of interrupted dialogue, and an explicitly new sentence follows. (Which is not what's happening here.)

Stylistically, most people would object to the how this sentence was formed, as it really makes more sense to break it into three separate sentences right where the dashes are. As it is, it becomes needlessly long, and somewhat difficult to parse, because you end up scanning back and forth to try to understand the punctuation as a whole.

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In North America, it's common to see em dashes without spaces. In the UK, it's common to see en dashes with spaces on either side. They both serve the same purpose, and it's simply a matter of style as to which is used.