In the town of my growing-up, the flora and fauna, such as they were, were stable. Extinction, although understood as awful, seemed exotic. The dodo had never roamed my New York suburb. The spotted owl, whose possible extinction shut down logging operations, and the tiny snail darter, an endangered fish that delayed a big dam, were in other states. There had never been Yangtze River dolphins in Tenafly, N.J.

But now the bell is tolling, crazily, insistently, for the animals of my childhood.

When I was about 10 and slogging around our local nature center, the news that a little olive-colored salamander called a newt had a secret identity as the “the red eft” — turning orange as it matured before morphing back to its original color — filled my own geeky little heart with joy. In the 1990s, when scientists became alarmed that the count of frogs, toads and salamanders was nose-diving, the news somehow disjointed my memories of that time.

Then there was the report last year that the number of birds in the United States and Canada had fallen by 29 percent over 50 years. I used to do some casual birding with my mother. Or perhaps not so casual: I remember striding into a meeting with the leader of my Cub Scout troop intent on earning three merit badges, all for imitating bird calls. I think five calls were required per badge; amused, he cut me off after 10 calls.

When I read about the bird report, I considered checking the specific numbers on my favorite childhood species, but then I reached the part that noted that even sparrows and robins had taken “steep losses.” I became dispirited and dropped the idea. In my head, my childhood bird list had just taken a 30 percent hit.

I’ve realized over time that my early memories — seemingly secure in the static web of the past — have a perplexing tendency to conform to information of the present. When I was 50, after one parent had died and the other had moved, I returned to Tenafly for three days as a kind of sightseer. I had fun but was mystified not to see any kids out on their bikes, my cohort’s sole means of transportation until we graduated high school. Familiar streets seemed deserted, like in a “Twilight Zone” episode.