Herbivores are animals that consume only plants for their dietary needs. The extinction of an herbivore would have a debilitating effect for the carnivores that probably fed on this type of animal. Now the carnivores have one less meal choice to choose from. So that will put a strain on the other animals considered prey for the carnivores. It potentially could have a positive/negative effect on the amount of vegetation available within the ecosystem. Positive, in that the plants this particular herbivore was consuming now are not being consumed; negative, in that the lack of plant consumption has now increased the competitiveness of all the plants struggling for survival. The balance between producers, herbivores, and carnivores is a delicate part in the maintenance of an established ecosystem. Interrupt too many links in the food chain, and the whole thing can come screeching to a halt.