If they were always in the red for both grassland and forest, i upgraded them to the next size pen. I tested these by putting each dinosaur in the enclosures pictured above and adding trees one by one until they were happy.

I’m just doing this so you know the smallest they’ll accept. Note 3: You don’t to make their exhibits as small as I’m showing. Note 2: The larger their exhibit, the more forgiving they are on required terrain. If you fill a open plain with water, it still counts as grassland. If you fill a area of trees with water, it still counts as Forest. Note 1: Water counts as whatever you put it on. Instead of using the hard to decipher numbers in the information panel of the dinosaurs, I’m going to classify each dinosaur as a Tiny to Huge exhibit based on their minimum requirements, and list their Tree or Grassland needs as ‘Very Low’ to “Very HIgh’ based on how much of their exhibit they want covered.