I understand this is a very old post, but I'm with Martin on "all but". I'm sure that you can tell, but I'm not particularly gifted in English theory. Anyway, what I find problematic with "all but" is that, while it may mean "almost" when followed by an adjective, if one has never been exposed to that phrasing and reads the sentence word-for-word, it has no conclusion.

"All" is synonymous with "anything" so, to just read it with out the special exemption, "all but " means literally anything but extinct. The population in question can be declining, increasing, remaining steady, anything! I guess I'm saying the same thing people who were citing "everything except" as how they interpreted it, and I understand idioms are exceptions by nature, but when it comes to "all" and "but", I can't think of a single context to makes either word a synonym for "almost" except for in the case of "all but".