Today, simultaneously, we have alpine, desert, tundra, savanna, forest, and other ecosystems - all at the same time, and each with respective fauna (animals) and flora (plants).
It was the same before the Flood. You would have had many different ecosystems thriving ALL AT THE SAME TIME, during the 1600 years. I will use the evolution-believed names, but without their mythical “sequence”. In the pre-Flood era, simultaneously, there were: jurassic, cretaceous, devonian, ordovician, silurian, and cambrian ecosystems - all thriving AT THE SAME TIME. That is what common sense shows, as it fits similar to what we see in the world today. -Creation, once again, consistent with common sense and with known science.