Vegetation makes the food for herbivorous and omnivorous animals in any area. If the vegetation of an area changes, such animals may migrate to other areas in search of food. In the absence of such herbivorous animals, the species of carnivorous animals may also migrate because now even they have to battle with the unavailability of food.
The given area then comes to be inhabited by animals that consume the particular kind of vegetation available. This is how when vegetation is altered animal life changes