There was an article posted here recently about fireflies disappearing. The conclusion was more that they have a rather limited range, and prefer certain (damp, wooded) environments, and it is these environments which are disappearing.
My skepticism is rooted in having fireflies where I lived 20 years ago in a neighborhood that wasn't new. Now, there are no fireflies there. Unless the die-off is very slow, my experience clashes with your report that their limited range / terraforming are to blame.
If the article is merely stating that terraforming has MORE of an impact than pesticides... well, that could be true merely because we build more than we spray.
To your point, I think a lot of folks forget how much "terraforming" we're doing all of the time. Entire expanses of grasslands and forests are growing and being re-leveled.
A look at Google maps satellite demonstrates changes of color (dark green to light green and vice versa) across parts of several continents, changes that ebb and flow in big ways over just decades. I think this would very much affect insect (and animal and plant) populations.
