How was the ecosystem affected by the introduction or extermination?

You see what had happened was

When you remove on introduce a new species into an ecosystem, it tends to throw everything out of balance. Imagine if a super-predator was introduced that killed all of another predator's prey. The normal predator would starve to death. If you were to remove the predator, then the prey might multiply rapidly without anything to cull their population. They might devour the food source of another prey that starves to death. If you introduced a super-plant, it might overrun the normal flora and 'cause those who relied on that to starve which leads to the predators who relied on those prey to starve. Nature is a delicate thing. A true balancing act between predator and prey.