Fraser Island in Queensland did not traditionally house Koala populations. However, since they were brought to the island they have provided benefits and have also caused problems. On a positive note, they are an attraction for tourists providing the island authorities with resources for maintenance. Conversely, they tend to disrupt the flora, even wiping out species of trees if they are not monitored. Thus, in order to maintain healthy populations without damage to the environment, the authorities can decide to cull a number of Koalas (inexpensive) or relocate to the mainland (expensive) where they are already well adapted. Additionally, animal welfare groups do not take kindly to culling.
Note: this is a fictitious example.