Can words like "darüber" or "darauf" etc. be used to refer back to a plural noun, or do you have to use constructions like über sie, auf sie etc?

In the case of replacing nouns with pronouns. "Wir haben über die Umwelt, die Kultur und die Landeskunde gelesen" - could we say "Wir haben darüber gelesen" or would this imply there was only one thing that we read about? In other words does "darüber" mean "about that/ it" only, or can it mean "about them". I'm presuming the same rule would apply to any of the other da+preposition words, like darauf, davon etc.