but.. it wouldn't happen that way (like throwing a switch). Crops would rot in the field and then be replaced by native plants. Is this evidence presented in paper(s)?
The moment the farmer dies without an heir, his field is fallow. From that point forward, whatever germinates will grow if it can compete. So pioneer species get free reign and they can spread widely in only a few years.
The little ice age was almost 300 years. From a geologic standpoint or even a glacial one, trees sprouting up all over in a five year time frame is pretty sudden, but the sudden event I was talking about was acreage of unmanaged land.
I hesitate to call it anthropogenic because it’s the opposite of that. I suppose the delay of the cold period counts, though.