“Back in the 1970s” is the problem. It’s not even a blink of an eye in terms of the planet. It’s a flash, it’s instantaneous. It looks like it’s happening in slow motion to us because we’re such short-lived creatures, but “back” in the 1970s is not even a flicker in geological time.
It’s accelerating too. In the 1990s there were insects everywhere where I grew up; playing outside was half playing with my friends and half playing with butterflies. Now there’s almost nothing.
Remember how many insects spattered on your parent’s car’s windows?
How many insects have you hit recently?
Edit: This also goes unnoticed because each generation grows up with their own “normal”. Less than 100 years ago a school of whales could stretch from horizon to horizon. Now we think of a school as a dozen or so of the beasts. Only another hundred or so years back from there, ships could see nothing but turtles all around them, stretching off into the distance; landlocked by shells.
Your kid catches a foot long fish and is delighted. No-one he knows has ever caught one that long! He’s the talk of the school until you show him a picture of one you caught at his age; it’s over twice as long! Your dad laughs, and pulls out the picture of the 6 foot one he and his friends caught at that age. Grandad shrugs and nods to the beams of the house; propped up by a 9 foot long fishbone.
Your grandkids are going to think that a minnow in the river is a newspaper-worthy event. “Normal” is whatever is there at the time.