there’s this classification called “trophic level”, which is basically a breakdown of how far removed a species is from getting energy directly from the sun

So we’re not seeing a planet wide die-off of plants because their source of energy is broadly unchanged (this becomes a different story when you start looking at how specific regions are changing). Insects are specifically vulnerable to a changing climate, as /u/beambrain points out. They tend to live short, fast lives and need a consistent intake of energy, water, and nutrients as they don’t have much in the way of long term storage (specific species may vary, this is in general). Overall, they’re immediately vulnerable to any large scale disruption in the environment, the first to feel those shocks.

Vertebrates tend to be one or two trophic levels removed from insects, with (comparatively) larger stores of energy to last them from meal to meal. This means they’re also a level removed from any shock to the overall flow of energy. This doesn’t mean they’re immune, just that any consequences are delayed. The shock has to flow through the lower levels first.

Now, he [David Wagner, entomologist and a professor of ecology] finds himself coming home empty-handed. “I just got back from Texas, and it was the most unsuccessful trip I’ve ever taken,” he says. “There just wasn’t any insect life to speak of.”

It was not only the insects missing, he says, it was everything. “Everything was crispy, fried; the lizard numbers were down to the lowest numbers I can ever remember. And then the things that eat lizards were not present – I didn’t see a single snake the entire time.”