The ecosytsem has a very fine balance. Each species is dependant on one another for food and population control. Introducing a new species such as the Cane Toad which has been introduced into Australia and Flordia and are extrmely invasive completly wipping out populations of Native species and are a huge problem. If you lose a population such as the wolves in yellow stone species such as elk will actually suffer from starvation and other issues due to lack of food etc because the wolves were not there for population control. But in some cases such as the wolves who were added back into Yellow stone it had a huge positive impact on species/populations.
