Big herbivores such as zebras and elephants are disappearing in huge numbers so much that they can potentially become extinct. William Ripple and his team focused on 74 species of large herbivores and came to the conclusion that they will continue to diminish in large numbers if something isn't done to intervene. According to Ripple this would come with great cost, ecologically, economically and socially. With this would also come the decline of carnivores, whose prey are going extinct. They also believe that with the loss of the herbivore population, other parts of the ecosystem will suffer. Besides lack of food for carnivores, there will be lack of seed dispersal, changes in habitat for fish, and slower nutrient cycles for plants.
See this link for more info on the topic:http://www.sciencedaily.com/releases/2015/05/150501151606.htm