I haven't been able to bring myself to go to war with the tree-hugging vermin lately.
First, I should point out that, over the course of the past year, I've cut around 500 logs my surface of trees in order to build a few above-ground dwellings constructed entirely out of palm (plus a marble masoleum / chapel, but thats aside the point), plus another 180 from the second cavern layer to beef up my danger rooms in preparation for Fun. They have no issues with this, apparently.
Secondly, in the last SINGULAR caravan, they brought me breeding pairs of alligators and jaguars.
Third... they don't seem to mind hauling away several hundred nearly worthless stone blocks with them every year. In fact, if anything, the cheap but heavy animals they bring with them every year (900 weight / 150 stone blocks for 400 dorfbucks) seem almost tailored to make them a stone disposal mechanism: my masons get experience, I get exotic animals, and they get... well, nothing useful, at least.
At the same time, though, I'm feeling rather undwarvenly for allowing the elves - who apparently don't care too much about the fact that one of the two tree types that grows in my area has disappeared - to freely come and go as they please...
I'm torn! They're elves, but... they're bringing me wild cats to fling at goblins, and helping me get rid of excess stone!