What would happen if a number of carnivores decreases in an ecosystem?

The following consequences may occur due to decrease in number of carnivores in an ecosystem.
(i) population of herbivores will increase due to absence of its predator
(ii) Plants will decrease in number or disappear from the system due to overgrazing by the herbivores
(iii) Both these factors may disturb the food chain and food webs thus affecting the ecosystem.