Large populations adapting or not adapting to change has gone on for thousands of years. Most ancient civilisations coped on their ears with this including Australian aborigines.
Those that did not starved or went down the aggressive ( one can add pestilence and disease ) route or moved - again normal outcomes for living things in the cycle of nature.
The various American Indian tribes made war on each other - food was limited and this balanced their numbers with the available food on offer, given their tech, level being just one example. South American populations simply left areas that became deserts over time. They famously made human sacrifices to appease the climate gods on their pyramid temples along the way. Unfortunately, @pintohoo their level is the level you are operating on. Religous zealotry with no foundation in facts but fear alone.
