You write beautifully and movingly. I had a very similar experience at age 12. There was a many miles long swath of woods and fields behind my family's backyard when I was growing up. I loved walking there, alone or with playmates. We found box turtles, frogs, lizards; we made short-lived ponds by damming the stream; and I learned many types of trees and flowers and their annual rhythms. One day surveying poles began appearing and a long straight new trail was cut. The entire swath had been designated to become a 6-lane highway. The stream would disappear into a culvert. Nearly the whole ecosystem would be destroyed. I was heartbroken. Eventually I learned that the highway plans had been in place for over a decade. State budget politics had delayed its construction. It was only because of the impending highway, that those woods had never been sold and developed for more suburban housing. In other words, the highway had actually "protected" that swath for all those years; and by being delayed, it had allowed me to enjoy them and connect with Nature in a way that remains a part of me 50+ years later. It feels strange to be grateful to a highway but like you say impermanence is the state of all things. I feel lucky to have had my woods for my formative years.