[rendang]

There's a great deal of land in the very cold part of the N hemisphere that may become more agriculturally productive with warming.

[wing-_-nuts]

The soil quality there is very low. Also, large parts of canada are covered by the 'canadian shield' which is basically where glaciers have scraped down to bare granite bedrock. If we had thousands of years to adjust, I'm sure we could manage but you're not planting huge fields of wheat, corn or soybean in that soil.

[Daishiman]

Those area are limited by the number of hours of sunlight and the number of growing seasons. Reductions in 20-30% are expected, but this doesn't really capture the increase in extreme weather events that can lead to total crop loss.