There was a study made in a UK forest in where it was calculated the population of red squirrels and grey squirrels. There was a clear competition and by the end of the study, there were only grey squirrels. How the decline of the red squirrel population might affect its native ecosystem??
Since grey squirrels can Camouflage... predators may not eat because the red squirrels die out. And grey squirrels may reproduce more because there is no competition anymore.