If all the plants died, then photosynthesis would not occur. Also, the primary consumers won't have any food to eat, because they are herbivores. Then the secondary consumers can't eat the primary consumers, because the primary consumers are dead due to a lack of food. Therefore the secondary consumers also die, and so do the tertiary consumers. However, some of these starving animals could move to a new environment, and find a niche and food their. After 10 - 20 years, secondary succession will take place, and the plants will grow back allowing for animals to live their once again.
Please Mark Brainliest if it helped!