[WalterBright]

Populations regularly outgrow their food supply and migrate. That isn't climate change. They also exhaust their land with poor farming practices, that isn't climate change, either.

[restalis]

"They also exhaust their land with poor farming practices, that isn't climate change, either."

The climate change adepts will argue with you on this one, as human induced (micro)climate change is still considered a climate change.