There was indeed a big mentality change. Significantly less casual pollution (Diemerzeedijk in Amsterdam North, the open chemical dump for Europe, comes to mind), and .. lots of the polluting industry outsourced to Asia, China mostly.

My personal impression is that there are way less insects than there used to be.

Edit: found an old HN comment about the relationship to Agent Orange production and Diemerzeedijk: https://news.ycombinator.com/item?id=9431741

I was actually searching an article about exploding chemical barrels now and then landing on fishing boats sailing in the area.