The behavior that can end up being more harmful than helpful is:
Iguanas and tortoises eat leaves, fruits, and flowers, relying on each as important seasonal food sources.
This is because their foraging can lead to overconsumption of certain plants, potentially harming the plants' ability to reproduce and thrive. In contrast, the other behaviors listed (pollination, seed dispersal, and territorial defense by hummingbirds) generally promote plant reproduction and survival.