Insect populations are declining in places like New England and the upper midwest despite farming both declining and finding more efficient ways to use fertilizer and pesticides on the same timeline.

If we're going down the road of human introduced chemical toxins (like pesticide pollution) I think a fair bit of blame also deserves to be laid at the feet of the state (and by proxy voters) for poisoning the soil immediately adjacent to roads (and to a slightly lesser degree, the watersheds) with various salts.