Lots of farms in ny. Flew over the Midwest a number of times and I can attest to your grain belt statement. But there still is vast tracks that are not farmed. There is still enough to keep a viable monarch population.
“There is still enough to keep a viable monarch population.”
Probably so, just with reduced numbers in the east. There are two Monarch migratory routes- the eastern route that terminates in Mexico and then the California route. California numbers shouldn’t be affected at all.