palaeobotany is a great tag.
When considering a new tag, ask yourself: firstly, have you got, or seen, questions relating to that tag? If not, then it is at least premature; and secondly, would it help people follow a particular subject that they're interested in? Are there people for whom a question would be of interest if it were about the US EPA, regardless of anything else to do with the question? Are there people who'd want to hide any questions that are something to do with the US EPA (because you can lower the visibility of particular tags, as well as increase it).
Remember, the search engine should pick up any of these sets of initials anyway. So it's easy to find posts that mention the EPA. Tags are for the classification of questions: and that's a different role than merely indexing references, because the search engine does that well anyway.