I have to guess due to differences they noticed in terms of specific diseases, medical conditions, migration patterns, population changes and/or population distribution over time. IANABiologist though so I’m interested to hear the answer also.

We could notice something going very wrong with the rate at which species go extinct.

Extinctions are normal. Extinctions due to human settlements are higher, and not good for the local environment, but we have been modelling them for years now.

Extinction rates due to global warming? It’s a catastrophe.