It is and you’re right, but there point op was making (perhaps not very well) is that a plain monoculture grass field is about as biodiverse as a car park. In order to be a sustainable ecological habitat for life more is needed than just grass.
Water, trees, bushes, flowering plants etc. These provide shade, places to nest and food that is needed for life to thrive.
A field is essentially an ecological wasteland.
Unfortunately the game continues however, and you just lost.