Answer:
Any ecosystem is designed with a particular necessity that drives it's entire organisms that is residing in the particular ecosystem. Invasion by other species would deprive the initial nutrients that are contained in an ecosystem for it's native species.
This in turn would gradually make the native species extinct. The ecosystem contains all the nutrients that are enough for its residents and it is perfectly balanced by the nature, but invasion of a non-native species would break the natural balance and create deficit.
