Drop in insect and butterfly numbers has nothing to do with climate change. It is due to pesticides being pumped in unprecedented quantities into nature and monoculture agriculture.
It doesn't have "nothing" to do with climate change. Climate change probably contributes to habitat loss as weather becomes less favourable for some species in areas where they could probably survive before.
Pesticide use the is cost you pay for cheap food, meat heavy diets, and other benefits of living in "western" society. Sure we could grow food without pesticides, but it would cost more. It might also require more land - which would probably also impact insect populations.
Before 50 years ago, it was at least debatable whether everyone knew. Now everyone knows. And has for at least a generation.
You fuck things up without realizing, then you get to be surprised they're fucked up. You spend 50 years doing it knowingly, you don't get to act shocked when insects numbers are plummeting and once per century forest fires are happening every year and France gets zero rain for all of Feb...
Welcome to the new normal. The one we all knowingly ordered.