Wolves are keystone species. In other words, if you were to take wolves out of their natural environment, it would be thrown out of balance and the ecosystem would collapse. For example, take away wolves, increase in deer, decrease in the plants the deer eat due to them eating more, decrease in all of the other animals that eat those plants, and then say the plants were all gone, the deer would die, and everything would be gone due to wolves being taken away from that environment.
