Well it seemed like a good idea at the time.

After wandering around the forest for a few minutes and realizing that if he finds the shooter he'll be able to get back home in time for supper, Mark decides that the only logical thing to do is climb a tree and see what he can see. This might be a good idea, or it might not. I'm not sure how thick Lost Forest is and how helpful climbing a tree will be if said tree puts you above the canopy. Seems to me like it might make finding the shooter more difficult, unless, of course, he has also decided to climb a tree. Then Mark will have to shimmy around the trunk to make sure that he's not hit when Elmer gets a clear shot in all of that fresh air. Looking at the tree he decided to climb, however, I think that Mark should also be prepared to bail out when it falls down because it's clearly dead or quickly heading that way. (You know, there was a tree fairly similar to that one in Space Quest II, and it fell over just a soon as Roger Wilco climbed it, and unless Mark needs to climb down a ravine/gorge, I think he might want to find a healthier specimen.) There are also the crows to deal with, and I think we can all be fairly certain that those buggers are not on Mark's side (and that Andy can't climb trees because he's a dog).

As Mark climbs up the dying tree, Elmer continues to wander about Lost Forest, now lost, tired, cranky, and wishing that he'd paid more attention at those Boy Scout meetings he attended when he was a lad. Just as he's about to give up hope, Elmer notices the crows, and at first thinks he scared them, but then sees Mark in the tree and changes his mind. (He also apparently changes perspective and distance too, since panel two gives the impression that he's just about standing under the tree while panel three seems to put quite a distance between the two. Oh well. Maybe time and distance are funny here. Perhaps the world has moved on and things aren't quite right.) He also seems to have decided that Mark is just too tempting a target to pass up. I hope Mark is wearing his bullet proof khaki, or that Elmer is out of bullets, otherwise this is going to turn into "Mark Trail's Adventures In Emergency Medicine," and informative as that might be, it won't do anything about those barrels that we can only assume are still leaking their hazardous contents onto the floor of Lost Forest.