In the early stages of highway development, their trend can still follow the landform, that is, along the edge of the river or forest. But now, the highway is ubiquitous, and the animal populations that could roam freely such as wolves and bears are divided into scattered. Compared with the populations of large animals, the populations of smaller animals have greater fluctuations in numbers and are more prone to mixed habitation.
The trend of highway development can be inferred from this text.