Movie Moments IX: And your job would be what?

Aside from the two guys who have to shield their eyes from the Death Star's laser beam, one of my favorite, lesser know, probably not even named, characters from Star Wars Episode IV: A New Hope would be the guy in the tower with the spear at the end of the film.  Every time that I see him standing at the top of that watchtower, just hanging out, holding on to the spear, I have to wonder why he's even there.  I mean, the guy looks to be sitting at the top of a cell tower and all he has to protect himself, and the secret rebel base, is a spear (and maybe a blaster if he's lucky).  You could say that he's a lookout, but that doesn't make much sense since the base is surrounded by a heavily forested area, so anything below the canopy is out of his sight, and anything big enough to be seen (like an AT-AT or an AT-ST) would just blast the guy away, and if the rebels have radar, there's no real need for him to be looking to the sky.  Besides, what could he possibly do if there was an attack?  Throw the spear at a TIE Fighter?  I'm not sure how effective that would be, and once he's thrown it, how else is he going to defend himself?  So many questions.  (Who knows, maybe he got in trouble and that's the punishment.  You get elected "Rebel not in an aircraft most likely to be blasted out of the sky during an attack.")  Still, it warms my heart every time that I see him standing there, doing his job, whatever it may be.