I think there could be multiple types of plants apart from just grass and normal plants 
lilly pads for the water as an aquatic plant cactuses for dry parts and maybe moss can evolve from microalgae and then develop into plants instead of a normal algae evolving into a giant plant to make it more realistic.
Also if you add small plants maybe you could add small animals(insects) but to avoid simulating millions of insects you can just make it so that every insect species lives in a specific area and has a specific population and you can use that information to generate insects close to the camera in random places when the player is nearby and when they go away and come back you can just generate them again in random places so you don't have to simulate things when they are not loaded and only when they have to be. Ngl I think the game could really use insects because imagine finding a giant mosquito irl it looks so weird so if you're trying to add arthropods it would be SO much better if they were small and only loaded when needed.