Deathworld av Harry Harrison
Från Wikipedia
Everything on the planet is deadly to humans. The large animals are strong enough to destroy small vehicles, while the small ones have neurotoxic venom. Even the plants are deadly. All microorganisms consume insufficiently protected tissue as quickly as acids. On top of all this, life evolves so quickly that even Kerk and his Pyrran crew have to be retrained upon their return in order to survive.
Jason now reveals all. Although all life on Pyrrus competes for survival individually, they react collectively to natural disasters. The grubbers, with the assistance of their talkers, have integrated themselves peacefully into the planet's ecosystem, killing only for food or in self-defense. The junkmen, however, think only of killing, and kill everything they can simply because they can. The animals and plants band together against the common threat and cooperate in trying to eliminate them, mutating to better kill humans. Jason proves this to the junkmen, first by having the grubbers safely handle one of the city's ultralethal species, then doing it himself. The city's science director pretends he is handling a training aid, and is able to do the same.