People complaining about wrecked ecosystems apparently don't remember what "monsters" are. Monsters are creatures made out of magic that spontaneously generate from the passive magic of an area. They aren't part of the normal ecosystem, and it shouldn't actually be possible to "exterminate" them without draining or destroying the magic of the land itself. It takes monsters a longer time to regenerate and respawn when they're outside of a dungeon, but they will eventually respawn. The fact that the Enrage Monster trick works at all is proof of this: normal creatures and humans wouldn't care at all about a big pile of magic sitting in the middle of a clearing, but it draws monsters to it immediately. If anything, doing a full area pull and then nuking all the monsters that show up is doing the ecosystem a favor, because all of the normal animal and plantlife have to live in a world where they're constantly terrorized and predated upon by supernatural freaks. You're giving the ecosystem a break for a few weeks by genociding the monster population.
Also, technology seems to be progressing extremely quickly. The students went from a bunch of yokels who can barely make air move with their hands to a dedicated magical combat engineering corp. We'll have spelljammers and stargates in no time at this rate. I wonder how long it will be before somebody puts together a magic gun.