Back when I was a kid, after a heavy downpour the roads would be crowded with earthworms. You really had to watch where you step to avoid stepping on one of those suckers. Fast forward today and I RARELY see a single worm out on the road after a similar downpour.
This reminds me of a passage in the book Sapiens, where the author muses that there may have been prehistoric tribes where grandparents told tales of when mammoths were so plentiful hunters would take them every month, and the grandchildren would smile and nod. The grandchildren would in turn grow up and tell their grandchildren that there were once beasts called mammoths, and these grandchildren too would smile and…
It's described more here - https://oceana.org/blog/daniel-pauly-and-george-monbiot-conv... and aptly illustrated here - https://oceana.org/sites/default/files/285468/catch_of_the_d...