How can invasive species be harmful?
An example was the introduction of rabbits in Australia. The rabbitns had no natural predators and were able to reproduce rapidly. The rabbits ate the grass causing starvation of other species that were native to Austria.
Starlings were another invasive species that disrupted the ecology of North America. After a period of time a new balance was achieved and the Starlings became part of the environment.
Invasive species upset the ecological balance of an environment. This causes damage to the ecological balance that might take years to rectify.