How could you have kids running around there with exploding rocks and poisonous dart throwing plants?
I think the idea was that those were defenses controlled by Vaal, and with Vaal shut down, they were deactivated. At least that's how the comics sequel mentioned above interpreted it.
Teaser: The Vaalians are seen again in my next Trek book, No Time Like the Past,
and I interpreted the exploding rocks somewhat differently.