The questions can have various level of localization. For example take that one: Do I need to worry about feral dogs or even wolves if I camp in random areas while hitchhiking in Georgia (the country)?. It is about camping in Georgia, but it could be formulated to target the whole Kaukasus, Middle Asia, or it could be something specify for trekking in Svanetia.
In my opinion, the tags should be used to organize questions. So the locality level of tags should be dependent on how much questions they are adequate for.
In the case of question linked by me, the most adequate tag would be [georgia], but there are too less questions about that region, so [kaukasus] would be enough. [asia], on the other way, would make no sense, because there are no specific outdoor issues related to the whole Asia. In case of this site, it is rational to assume, that geographic tags should not be broader that some climatic zone, because it's the factor that makes most difference when being outdoor.
I would create more specific, subregional tags, when the regional tag has at least a few dozen questions.